Category Archives: Evolutionary Psychology

‘Wise Man’, Sapiens, A Brief History of Humankind – Dr Yuval Noah Harari.

Just 6 million years ago, a single female ape had two daughters. One became the ancestor of all chimpanzees, the other is our own grandmother.

From about 2 million years ago until around 10,000 years ago, the world was home, at one and the same time, to several human species. And why not? Today there are many species of foxes, bears and pigs. The earth of a hundred millennia ago was walked by at least six different species of man. It’s our current exclusivity, not that multi-species past, that is peculiar and perhaps incriminating.

It is unsettling and perhaps thrilling to think that we Sapiens could at one time have sex with an animal from a different species, and produce children together. Tolerance is not a Sapiens trademark. As we will see, we Sapiens have good reasons to repress the memory of our siblings.

Sapiens can cooperate in extremely flexible ways with countless numbers of strangers. That’s why Sapiens rule the world, whereas ants eat our leftovers and chimps are locked up in zoos and research laboratories.

100,000 years ago, at least six human species inhabited the earth. Today there is just one.

Us, Homo sapiens.

How did our species succeed in the battle for dominance? Why did our foraging ancestors come together to create cities and kingdoms? How did we come to believe in gods, nations and human rights; to trust money, books and laws; and to be enslaved by bureaucracy, consumerism and the pursuit of happiness? And what will our world be like in the millennia to come?

Bold, wide-ranging and provocative, Sapiens challenges everything we thought we knew about being human: our beliefs, our actions, our power and our future.

About the Author

“I encourage all of us, whatever our beliefs, to question the basic narratives of our world, to connect past developments with present concerns, and not to be afraid of controversial issues.”

Dr Yuval Noah Harari has a PhD in History from the University of Oxford and now lectures at the Hebrew University of Jerusalem, specialising in World History. His research focuses on broad questions, such as:

What is the relation between history and biology? Is there justice in history? Did people become happier as history unfolded?

65,000 people have signed up to Harari’s online course, A Brief History of Humankind. Sapiens is an international bestseller and is published in more than 20 languages worldwide. In 2012 Harari was awarded the annual Polonsky Prize for Creativity and Originality in the Humanistic Disciplines.

PART ONE

The Cognitive Revolution

1. An Animal of No Significance

ABOUT 13.5 BILLION YEARS ago, matter, energy, time and space came into being in what is known as the Big Bang. The story of these fundamental features of our universe is called physics.

About 300,000 years after their appearance, matter and energy started to coalesce into complex structures, called atoms, which then combined into molecules. The story of atoms, molecules and their interactions is called chemistry.

About 3.8 billion years ago, on a planet called Earth, certain molecules combined to form particularly large and intricate structures called organisms. The story of organisms is called biology.

About 70,000 years ago, organisms belonging to the species Homo sapiens started to form even more elaborate structures called cultures. The subsequent development of these human cultures is called history.

Three important revolutions shaped the course of history: the Cognitive Revolution kick-started history about 70,000 years ago. The Agricultural Revolution sped it up about 12,000 years ago. The Scientific Revolution, which got under way only 500 years ago, may well end history and start something completely different.

This book tells the story of how these three revolutions have affected humans and their fellow organisms.

There were humans long before there was history. Animals much like modern humans first appeared about 2.5 million years ago. But for countless generations they did not stand out from the myriad other organisms with which they shared their habitats.

On a hike in East Africa 2 million years ago, you might well have encountered a familiar cast of human characters: anxious mothers cuddling their babies and clutches of carefree children playing in the mud; temperamental youths chafing against the dictates of society and weary elders who just wanted to be left in peace; chest-thumping machos trying to impress the local beauty and wise old matriarchs who had already seen it all. These archaic humans loved, played, formed close friendships and competed for status and power but so did chimpanzees, baboons and elephants. There was nothing special about humans. Nobody, least of all humans themselves, had any inkling that their descendants would one day walk on the moon, split the atom, fathom the genetic code and write history books. The most important thing to know about prehistoric humans is that they were insignificant animals with no more impact on their environment than gorillas, fireflies or jellyfish.

Biologists classify organisms into species. Animals are said to belong to the same species if they tend to mate with each other, giving birth to fertile offspring. Horses and donkeys have a recent common ancestor and share many physical traits. But they show little sexual interest in one another. They will mate if induced to do so but their offspring, called mules, are sterile. Mutations in donkey DNA can therefore never cross over to horses, or vice versa. The two types of animals are consequently considered two distinct species, moving along separate evolutionary paths. By contrast, a bulldog and a spaniel may look very different, but they are members of the same species, sharing the same DNA pool. They will happily mate and their puppies will grow up to pair off with other dogs and produce more puppies.

Species that evolved from a common ancestor are bunched together under the heading ‘genus’ (plural genera). Lions, tigers, leopards and jaguars are different species within the genus Panthera. Biologists label organisms with a two-part Latin name, genus followed by species. Lions, for example, are called Panthera Leo, the species leo of the genus Panthera. Presumably, everyone reading this book is a Homo sapiens the species sapiens (wise) of the genus Homo (man).

Genera in their turn are grouped into families, such as the cats (lions, Cheetahs, house cats), the dogs (wolves, foxes, jackals) and the elephants (elephants, mammoths, mastodons). All members of a family trace their lineage back to a founding matriarch or patriarch. All cats, for example, from the smallest house kitten to the most ferocious lion, share a common feline ancestor who lived about 25 million years ago.

Homo sapiens, too, belongs to a family. This banal fact used to be one of history’s most closely guarded secrets. Homo sapiens long preferred to view itself as set apart from animals, an orphan bereft of family, lacking siblings or cousins, and, most importantly, without parents. But that’s just not the case. Like it or not, we are members of a large and particularly noisy family called the great apes. Our closest living relatives include chimpanzees, gorillas and orangutans. The chimpanzees are the closest. Just 6 million years ago, a single female ape had two daughters. One became the ancestor of all chimpanzees, the other is our own grandmother.

Skeletons in the Closet

Homo sapiens has kept hidden an even more disturbing secret. Not only do we possess an abundance of uncivilised cousins, once upon a time we had quite a few brothers and sisters as well. We are used to thinking about ourselves as the only humans, because for the last 10,000 years, our species has indeed been the only human species around. Yet the real meaning of the word human is ‘an animal belonging to the genus Homo’, and there used to be many other species of this genus besides Homo sapiens. Moreover, as we shall see in the last chapter of the book, in the not-so-distant future we might again have to contend with non-sapiens humans. To clarify this point, I will often use the term ‘Sapiens’ to denote members of the species Homo sapiens, while reserving the term ‘human’ to refer to all extant members of the genus Homo.

Humans first evolved in East Africa about 2.5 million years ago from an earlier genus of apes called Australopithecus, which means ‘Southern Ape’. About 2 million years ago, some of these archaic men and women left their homeland to journey through and settle vast areas of North Africa, Europe and Asia. Since survival in the snowy forests of northern Europe required different traits than those needed to stay alive in Indonesia’s steaming jungles, human populations evolved in different directions. The result was several distinct species, to each of which scientists have assigned a pompous Latin name.

Humans in Europe and western Asia evolved into Homo neanderthalensis (‘Man from the Neander Valley’), popularly referred to simply as ‘Neanderthals’. Neanderthals, bulkier and more muscular than us Sapiens, were well adapted to the cold climate of Ice Age western Eurasia. The more eastern regions of Asia were populated by Homo erectus, ‘Upright Man’, who survived there for close to 2 million years, making it the most durable human species ever. This record is unlikely to be broken even by our own species. It is doubtful whether Homo sapiens will still be around a thousand years from now, so 2 million years is really out of our league.

On the island of Java, in Indonesia, lived Homo soloensis, ‘Man from the Solo Valley’, who was suited to life in the tropics. On another Indonesian island the small island of Flores archaic humans underwent a process of dwarfing. Humans first reached Flores when the sea level was exceptionally low, and the island was easily accessible from the mainland. When the seas rose again, some people were trapped on the island, which was poor in resources. Big people, who need a lot of food, died first. Smaller fellows survived much better. Over the generations, the people of Flores became dwarves. This unique species, known by scientists as Homo floresiensis, reached a maximum height of only one metre and weighed no more than twenty-five kilograms. They were nevertheless able to produce stone tools, and even managed occasionally to hunt down some of the island’s elephants though, to be fair, the elephants were a dwarf species as well.

In 2010 another lost sibling was rescued from oblivion, when scientists excavating the Denisova Cave in Siberia discovered a fossilised finger bone. Genetic analysis proved that the finger belonged to a previously unknown human species, which was named Homo denisova. Who knows how many lost relatives of ours are waiting to be discovered in other caves, on other islands, and in other climes?

While these humans were evolving in Europe and Asia, evolution in East Africa did not stop. The cradle of humanity continued to nurture numerous new Species, such as Homo rudolfensis, ‘Man from Lake Rudolf’, Homo ergaster, ‘Working Man’, and eventually our own species, which we’ve immodestly named Homo sapiens, ‘Wise Man’.

The members of some of these species were massive and others were dwarves. Some were fearsome hunters and others meek plant-gatherers. Some lived only on a single island, while many roamed over continents. But all of them belonged to the genus Homo. They were all human beings.

It’s a common fallacy to envision these species as arranged in a straight line of descent, with Ergaster begetting Erectus, Erectus begetting the Neanderthals, and the Neanderthals evolving into us. This linear model gives the mistaken impression that at any particular moment only one type of human inhabited the earth, and that all earlier species were merely older models of ourselves.

The truth is that from about 2 million years ago until around 10,000 years ago, the world was home, at one and the same time, to several human species. And why not? Today there are many species of foxes, bears and pigs. The earth of a hundred millennia ago was walked by at least six different species of man. It’s our current exclusivity, not that multi-species past, that is peculiar and perhaps incriminating. As we will shortly see, we Sapiens have good reasons to repress the memory of our siblings.

The Cost of Thinking

Despite their many differences, all human species share several defining characteristics. Most notably, humans have extraordinarily large brains compared to other animals. Mammals weighing sixty kilograms have an average brain size of 200 cubic centimetres. The earliest men and women, 2.5 million years ago, had brains of about 600 cubic centimetres. Modern Sapiens sport a brain averaging 1,200-1,400 cubic centimetres. Neanderthal brains were even bigger.

That evolution should select for larger brains may seem to us like, well, a no-brainer. We are so enamoured of our high intelligence that we assume that when it comes to cerebral power, more must be better. But if that were the case, the feline family would also have produced cats who could do calculus, and frogs would by now have launched their own space programme. Why are giant brains so rare in the animal kingdom?

The fact is that a jumbo brain is a jumbo drain on the body. It’s not easy to carry around, especially when encased inside a massive skull. It’s even harder to fuel. In Homo sapiens, the brain accounts for about 2-3 per cent of total body weight, but it consumes 25 per cent of the body’s energy when the body is at rest. By comparison, the brains of other apes require only 8 per cent of rest-time energy.

Archaic humans paid for their large brains in two ways. Firstly, they spent more time in search of food. Secondly, their muscles atrophied. Like a government diverting money from defence to education, humans diverted energy from biceps to neurons. It’s hardly a foregone conclusion that this is a good strategy for survival on the savannah. A chimpanzee can’t win an argument with a Homo sapiens, but the ape can rip the man apart like a rag doll.

Today our big brains pay off nicely, because we can produce cars and guns that enable us to move much faster than chimps, and shoot them from a safe distance instead of wrestling. But cars and guns are a recent phenomenon. For more than 2 million years, human neural networks kept growing and growing, but apart from some flint knives and pointed sticks, humans had precious little to show for it.

What then drove forward the evolution of the massive human brain during those 2 million years? Frankly, we don’t know.

Another singular human trait is that we walk upright on two legs. Standing up, it’s easier to scan the savannah for game or enemies, and arms that are unnecessary for locomotion are freed for other purposes, like throwing stones or signalling. The more things these hands could do, the more successful their owners were, so evolutionary pressure brought about an increasing concentration of nerves and finely tuned muscles in the palms and fingers. As a result, humans can perform very intricate tasks with their hands. In particular, they can produce and use sophisticated tools. The first evidence for tool production dates from about 2.5 million years ago, and the manufacture and use of tools are the criteria by which archaeologists recognise ancient humans.

Yet walking upright has its downside. The skeleton of our primate ancestors developed for millions of years to support a creature that walked on all fours and had a relatively small head. Adjusting to an upright position was quite a challenge, especially when the scaffolding had to support an extra-large cranium. Humankind paid for its lofty vision and industrious hands with backaches and stiff necks.

Women paid extra. An upright gait required narrower hips, constricting the birth canal and this just when babies’ heads were getting bigger and bigger. Death in childbirth became a major hazard for human females. Women who gave birth earlier, when the infant’s brain and head were still relatively small and supple, fared better and lived to have more children. Natural selection consequently favoured earlier births. And, indeed, compared to other animals, humans are born prematurely, when many of their vital systems are still underdeveloped. A colt can trot shortly after birth; a kitten leaves its mother to forage on its own when it is just a few weeks old. Human babies are helpless, dependent for many years on their elders for sustenance, protection and education.

This fact has contributed greatly both to humankind’s extraordinary social abilities and to its unique social problems. Lone mothers could hardly forage enough food for their offspring and themselves with needy children in tow. Raising children required constant help from other family members and neighbours.

It takes a tribe to raise a human. Evolution thus favoured those capable of forming strong social ties.

In addition, since humans are born underdeveloped, they can be educated and socialised to a far greater extent than any other animal. Most mammals emerge from the womb like glazed earthenware emerging from a kiln, any attempt at remoulding will only scratch or break them. Humans emerge from the womb like molten glass from a furnace. They can be spun, stretched and shaped with a surprising degree of freedom. This is why today we can educate our children to become Christian or Buddhist, capitalist or socialist, warlike or peace-loving.

We assume that a large brain, the use of tools, superior learning abilities and complex social structures are huge advantages. It seems selfevident that these have made humankind the most powerful animal on earth. But humans enjoyed all of these advantages for a full 2 million years during which they remained weak and marginal creatures. Thus humans who lived a million years ago, despite their big brains and sharp stone tools, dwelt in constant fear of predators, rarely hunted large game, and subsisted mainly by gathering plants, scooping up insects, stalking small animals, and eating the carrion left behind by other more powerful carnivores.

One of the most common uses of early stone tools was to crack open bones in order to get to the marrow. Some researchers believe this was our original niche. Just as woodpeckers specialise in extracting insects from the trunks of trees, the first humans specialised in extracting marrow from bones. Why marrow? Well, suppose you observe a pride of lions take down and devour a giraffe. You wait patiently until they’re done. But it’s still not your turn because first the hyenas and jackals and you don’t dare interfere with them scavenge the leftovers. Only then would you and your band dare approach the carcass, look cautiously left and right and dig into the edible tissue that remained.

This is a key to understanding our history and psychology. Genus Homo’s position in the food chain was, until quite recently, solidly in the middle. For millions of years, humans hunted smaller creatures and gathered what they could, all the while being hunted by larger predators. It was only 400,000 years ago that several species of man began to hunt large game on a regular basis, and only in the last 100,000 years with the rise of Homo sapiens that man jumped to the top of the food chain.

That spectacular leap from the middle to the top had enormous consequences. Other animals at the top of the pyramid, such as lions and sharks, evolved into that position very gradually, over millions of years. This enabled the ecosystem to develop checks and balances that prevent lions and sharks from wreaking too much havoc. As lions became deadlier, so gazelles evolved to run faster, hyenas to cooperate better, and rhinoceroses to be more badtempered. In contrast, humankind ascended to the top so quickly that the ecosystem was not given time to adjust. Moreover, humans themselves failed to adjust. Most top predators of the planet are majestic creatures. Millions of years of dominion have filled them with self-confidence. Sapiens by contrast is more like a banana-republic dictator. Having so recently been one of the underdogs of the savannah, we are full of fears and anxieties over our position, which makes us doubly cruel and dangerous. Many historical calamities, from deadly wars to ecological catastrophes, have resulted from this over-hasty jump.

A Race of Cooks

A significant step on the way to the top was the domestication of fire. Some human species may have made occasional use of fire as early as 800,000 years ago. By about 300,000 years ago, Homo erectus, Neanderthals and the forefathers of Homo sapiens were using fire on a daily basis. Humans now had a dependable source of light and warmth, and a deadly weapon against prowling lions. Not long aftenwards, humans may even have started deliberately to torch their neighbourhoods. A carefully managed fire could turn impassable barren thickets into prime grasslands teeming with game. In addition, once the fire died down, Stone Age entrepreneurs could walk through the smoking remains and harvest charcoaled animals, nuts and tubers.

But the best thing fire did was cook. Foods that humans cannot digest in their natural forms such as wheat, rice and potatoes became staples of our diet thanks to cooking. Fire not only changed food’s chemistry, it changed its biology as well. Cooking killed germs and parasites that infested food. Humans also had a far easier time chewing and digesting old favourites such as fruits, nuts, insects and carrion if they were cooked. Whereas chimpanzees spend five hours a day chewing raw food, a single hour suffices for people eating cooked food.

The advent of cooking enabled humans to eat more kinds of food, to devote less time to eating, and to make do with smaller teeth and shorter intestines. Some scholars believe there is a direct link between the advent of cooking, the shortening of the human intestinal tract, and the growth of the human brain. Since long intestines and large brains are both massive energy consumers, it’s hard to have both. By shortening the intestines and decreasing their energy consumption, cooking inadvertently opened the way to the jumbo brains of Neanderthals and Sapiens.

Fire also opened the first significant gulf between man and the other animals. The power of almost all animals depends on their bodies: the strength of their muscles, the size of their teeth, the breadth of their wings. Though they may harness winds and currents, they are unable to control these natural forces, and are always constrained by their physical design. Eagles, for example, identify thermal columns rising from the ground, spread their giant wings and allow the hot air to lift them upwards. Yet eagles cannot control the location of the columns, and their maximum carrying capacity is strictly proportional to their wingspan.

When humans domesticated fire, they gained control of an obedient and potentially limitless force. Unlike eagles, humans could choose when and where to ignite a flame, and they were able to exploit fire for any number of tasks. Most importantly, the power of fire was not limited by the form, structure or strength of the human body. A single woman with a flint or fire stick could burn down an entire forest in a matter of hours. The domestication of fire was a sign of things to come.

Our Brothers’ Keepers

Despite the benefits of fire, 150,000 years ago humans were still marginal creatures. They could now scare away lions, warm themselves during cold nights, and burn down the occasional forest. Yet counting all species together, there were still no more than perhaps a million humans living between the Indonesian archipelago and the Iberian peninsula, a mere blip on the ecological radar.

Our own species, Homo sapiens, was already present on the world stage, but so far it was just minding its own business in a corner of Africa. We don’t know exactly where and when animals that can be classified as Homo sapiens first evolved from some earlier type of humans, but most scientists agree that by 150,000 years ago, East Africa was populated by Sapiens that looked just like us. If one of them turned up in a modern morgue, the local pathologist would notice nothing peculiar. Thanks to the blessings of fire, they had smaller teeth and jaws than their ancestors, whereas they had massive brains, equal in size to ours.

Scientists also agree that about 70,000 years ago, Sapiens from East Africa spread into the Arabian peninsula, and from there they quickly overran the entire Eurasian landmass.

When Homo sapiens landed in Arabia, most of Eurasia was already settled by other humans. What happened to them? There are two conflicting theories. The ‘Interbreeding Theory’ tells a story of attraction, sex and mingling. As the African immigrants spread around the world, they bred with other human populations, and people today are the outcome of this interbreeding.

For example, when Sapiens reached the Middle East and Europe, they encountered the Neanderthals. These humans were more muscular than Sapiens, had larger brains, and were better adapted to cold climes. They used tools and fire, were good hunters, and apparently took care of their sick and infirm. (Archaeologists have discovered the bones of Neanderthals who lived for many years with severe physical handicaps, evidence that they were cared for by their relatives.) Neanderthals are often depicted in caricatures as the archetypical brutish and stupid ‘cave people’, but recent evidence has changed their image.

According to the Interbreeding Theory, when Sapiens spread into Neanderthal lands, Sapiens bred with Neanderthals until the two populations merged. If this is the case, then today’s Eurasians are not pure Sapiens. They are a mixture of Sapiens and Neanderthals. Similarly, when Sapiens reached East Asia, they interbred with the local Erectus, so the Chinese and Koreans are a mixture of Sapiens and Erectus.

The opposing view, called the ‘Replacement Theory’ tells a very different story, one of incompatibility, revulsion, and perhaps even genocide. According to this theory, Sapiens and other humans had different anatomies, and most likely different mating habits and even body odours. They would have had little sexual interest in one another. And even if a Neanderthal Romeo and a Sapiens Juliet fell in love, they could not produce fertile children, because the genetic gulf separating the two populations was already unbridgeable. The two populations remained completely distinct, and when the Neanderthals died out, or were killed off, their genes died with them. According to this view, Sapiens replaced all the previous human populations without merging with them. If that is the case, the lineages of all contemporary humans can be traced back, exclusively, to East Africa, 70,000 years ago. We are all ‘pure Sapiens’.

A lot hinges on this debate. From an evolutionary perspective, 70,000 years is a relatively short interval. If the Replacement Theory is correct, all living humans have roughly the same genetic baggage, and racial distinctions among them are negligible. But if the Interbreeding Theory is right, there might well be genetic differences between Africans, Europeans and Asians that go back hundreds of thousands of years. This is political dynamite, which could provide material for explosive racial theories.

In recent decades the Replacement Theory has been the common wisdom in the field. It had firmer archaeological backing, and was more politically correct (scientists had no desire to open up the Pandora’s box of racism by claiming significant genetic diversity among modern human populations). But that ended in 2010, when the results of a four-year effort to map the Neanderthal genome were published. Geneticists were able to collect enough intact Neanderthal DNA from fossils to make a broad comparison between it and the DNA of contemporary humans. The results stunned the scientific community.

It turned out that 1-4 per cent of the unique human DNA of modern populations in the Middle East and Europe is Neanderthal DNA. That’s not a huge amount, but it’s significant. A second shock came several months later, when DNA extracted from the fossilised finger from Denisova was mapped. The results proved that up to 6 per cent of the unique human DNA of modern Melanesians and Aboriginal Australians is Denisovan DNA.

If these results are valid, and it’s important to keep in mind that further research is under way and may either reinforce or modify these conclusions, the Interbreeders got at least some things right. But that doesn’t mean that the Replacement Theory is completely wrong. Since Neanderthals and Denisovans contributed only a small amount of DNA to our present-day genome, it is impossible to speak of a ‘merger’ between Sapiens and other human species. Although differences between them were not large enough to completely prevent fertile intercourse, they were sufficient to make such contacts very rare.

How then should we understand the biological relatedness of Sapiens, Neanderthals and Denisovans? Clearly, they were not completely different species like horses and donkeys. On the other hand, they were not just different populations of the same species, like bulldogs and spaniels. Biological reality is not black and white. There are also important grey areas. Every two species that evolved from a common ancestor, such as horses and donkeys, were at one time just two populations of the same species, like bulldogs and spaniels. There must have been a point when the two populations were already quite different from one another, but still capable on rare occasions of having sex and producing fertile offspring. Then another mutation severed this last connecting thread, and they went their separate evolutionary ways.

It seems that about 50,000 years ago, Sapiens, Neanderthals and Denisovans were at that borderline point. They were almost, but not quite, entirely separate species. As we shall see in the next chapter, Sapiens were already very different from Neanderthals and Denisovans, not only in their genetic code and physical traits, but also in their cognitive and social abilities, yet it appears it was still just possible, on rare occasions, for a Sapiens and a Neanderthal to produce a fertile offspring. So the populations did not merge, but a few lucky Neanderthal genes did hitch a ride on the Sapiens Express.

It is unsettling and perhaps thrilling to think that we Sapiens could at one time have sex with an animal from a different species, and produce children together.

But if the Neanderthals, Denisovans and other human species didn’t merge with Sapiens, why did they vanish? One possibility is that Homo sapiens drove them to extinction. Imagine a Sapiens band reaching a Balkan valley where Neanderthals had lived for hundreds of thousands of years. The newcomers began to hunt the deer and gather the nuts and berries that were the Neanderthals’ traditional staples. Sapiens were more proficient hunters and gatherers thanks to better technology and superior social skills so they multiplied and spread. The less resourceful Neanderthals found it increasingly difficult to feed themselves. Their population dwindled and they slowly died out, except perhaps for one or two members who joined their Sapiens neighbours.

Another possibility is that competition for resources flared up into violence and genocide.

Tolerance is not a Sapiens trademark. In modern times, a small difference in skin colour, dialect or religion has been enough to prompt one group of Sapiens to set about exterminating another group. Would ancient Sapiens have been more tolerant towards an entirely different human species? It may well be that when Sapiens encountered Neanderthals, the result was the first and most significant ethnic-cleansing campaign in history.

Whichever way it happened, the Neanderthals, and the other human species, pose one of history’s great what ifs. Imagine how things might have turned out had the Neanderthals or Denisovans survived alongside Homo sapiens. What kind of cultures, societies and political structures would have emerged in a world where several different human species coexisted? How, for example, would religious faiths have unfolded? Would the book of Genesis have declared that Neanderthals descend from Adam and Eve, would Jesus have died for the sins of the Denisovans, and would the Qur’an have reserved seats in heaven for all righteous humans, whatever their species? Would Neanderthals have been able to serve in the Roman legions, or in the sprawling bureaucracy of imperial China? Would the American Declaration of Independence hold as a self-evident truth that all members of the genus Homo are created equal? Would Karl Marx have urged workers of all species to unite?

Over the past 10,000 years, Homo sapiens has grown so accustomed to being the only human species that it’s hard for us to conceive of any other possibility. Our lack of brothers and sisters makes it easier to imagine that we are the epitome of creation, and that a chasm separates us from the rest of the animal kingdom.

When Charles Darwin indicated that Homo sapiens was just another kind of animal, people were outraged. Even today many refuse to believe it. Had the Neanderthals survived, would we still imagine ourselves to be a creature apart? Perhaps this is exactly why our ancestors wiped out the Neanderthals. They were too familiar to ignore, but too different to tolerate.

Whether Sapiens are to blame or not, no sooner had they arrived at a new location than the native population became extinct. The last remains of Homo soloensis are dated to about 50,000 years ago. Homo denisova disappeared shortly thereafter. Neanderthals made their exit roughly 30,000 years ago. The last dwarf-like humans vanished from Flores Island about 12,000 years ago. They left behind some bones, stone tools, a few genes in our DNA and a lot of unanswered questions. They also left behind us, Homo sapiens, the last human specks.

What was the Sapiens’ secret of success? How did we manage to settle so rapidly in so many distant and ecologically different habitats? How did we push all other human species into oblivion? Why couldn’t even the strong, brainy, cold-proof Neanderthals survive our onslaught? The debate continues to rage. The most likely answer is the very thing that makes the debate possible: Homo sapiens conquered the world thanks above all to its unique language.

2. The Tree of Knowledge

IN THE PREVIOUS chapter we saw that although Sapiens had already populated East Africa 150,000 years ago, they began to overrun the rest of planet Earth and drive the other human species to extinction only about 70,000 years ago. In the intervening millennia, even though these archaic Sapiens looked just like us and their brains were as big as ours, they did not enjoy any marked advantage over other human species, did not produce particularly sophisticated tools, and did not accomplish any other special feats.

In fact, in the first recorded encounter between Sapiens and Neanderthals, the Neanderthals won. About 100,000 years ago, some Sapiens groups migrated north to the Levant, which was Neanderthal territory, but failed to secure a firm footing. It might have been due to nasty natives, an inclement climate, or unfamiliar local parasites. Whatever the reason, the Sapiens eventually retreated, leaving the Neanderthals as masters of the Middle East.

This poor record of achievement has led scholars to speculate that the internal structure of the brains of these Sapiens was probably different from ours. They looked like us, but their cognitive abilities, learning, remembering, communicating were far more limited. Teaching such an ancient Sapiens English, persuading him of the truth of Christian dogma, or getting him to understand the theory of evolution would probably have been hopeless undertakings. Conversely, we would have had a very hard time learning his language and understanding his way of thinking.

But then, beginning about 70,000 years ago, Homo sapiens started doing very special things. Around that date Sapiens bands left Africa for a second time. This time they drove the Neanderthals and all other human species not only from the Middle East, but from the face of the earth. Within a remarkably short period, Sapiens reached Europe and East Asia. About 45,000 years ago, they somehow crossed the open sea and landed in Australia a continent hitherto untouched by humans. The period from about 70,000 years ago to about 30,000 years ago witnessed the invention of boats, oil lamps, bows and arrows and needles (essential for sewing warm clothing). The first objects that can reliably be called art date from this era (see the Stadel lion-man hem), as does the first clear evidence for religion, commerce and social stratification.

Most researchers believe that these unprecedented accomplishments were the product of a revolution in Sapiens’ cognitive abilities. They maintain that the people who drove the Neanderthals to extinction, settled Australia, and carved the Stadel lion-man were as intelligent, creative and sensitive as we are. If we were to come across the artists of the Stadel Cave, we could learn their language and they ours. We’d be able to explain to them everything we know from the adventures of Alice in Wonderland to the paradoxes of quantum physics and they could teach us how their people view the world.

The Cognitive Revolution

The appearance of new ways of thinking and communicating, between 70,000 and 30,000 years ago, constitutes the Cognitive Revolution. What caused it? We’re not sure. The most commonly believed theory argues that accidental genetic mutations changed the inner wiring of the brains of Sapiens, enabling them to think in unprecedented ways and to communicate using an altogether new type of language. We might call it the Tree of Knowledge mutation.

Why did it occur in Sapiens DNA rather than in that of Neanderthals? It was a matter of pure chance, as far as we can tell. But it’s more important to understand the consequences of the Tree of Knowledge mutation than its causes. What was so special about the new Sapiens language that it enabled us to conquer the world?

It was not the first language. Every animal has some kind of language. Even insects, such as bees and ants, know how to communicate in sophisticated ways, informing one another of the whereabouts of food. Neither was it the first vocal language. Many animals, including all ape and monkey species, have vocal languages. For example, green monkeys use calls of various kinds to communicate. Zoologists have identified one call that means ‘Careful! An eagle!’ A slightly different call warns ‘Careful! A lion!’ When researchers played a recording of the first call to a group of monkeys, the monkeys stopped what they were doing and looked upwards in fear. When the same group heard a recording of the second call, the lion warning, they quickly scrambled up a tree.

Sapiens can produce many more distinct sounds than green monkeys, but whales and elephants have equally impressive abilities. A parrot can say anything Albert Einstein could say, as well as mimicking the sounds of phones ringing, doors slamming and sirens wailing. Whatever advantage Einstein had over a parrot, it wasn’t vocal. What, then, is so special about our language?

The most common answer is that our language is amazingly supple. We can connect a limited number of sounds and signs to produce an infinite number of sentences, each with a distinct meaning. We can thereby ingest, store and communicate a prodigious amount of information about the surrounding world. A green monkey can yell to its comrades, ‘Careful! A lion!’ But a modern human can tell her friends that this morning, near the bend in the river, she saw a lion tracking a herd of bison. She can then describe the exact location, including the different paths leading to the area. With this information, the members of her band can put their heads together and discuss whether they should approach the river, chase away the lion, and hunt the bison.

A second theory agrees that our unique language evolved as a means of sharing information about the world. But the most important information that needed to be conveyed was about humans, not about lions and bison. Our language evolved as a way of gossiping.

According to this theory Homo sapiens is primarily a social animal. Social cooperation is our key for survival and reproduction. It is not enough for individual men and women to know the whereabouts of lions and bison. It’s much more important for them to know who in their band hates whom, who is sleeping with whom, who is honest, and who is a cheat.

The amount of information that one must obtain and store in order to track the ever-changing relationships of even a few dozen individuals is staggering. (In a band of fifty individuals, there are 1,225 one-on-one relationships, and countless more complex social combinations.) All apes show a keen interest in such social information, but they have trouble gossiping effectively.

Neanderthals and archaic Homo sapiens probably also had a hard time talking behind each other’s backs, a much maligned ability which is in fact essential for cooperation in large numbers. The new linguistic skills that modern Sapiens acquired about seventy millennia ago enabled them to gossip for hours on end. Reliable information about who could be trusted meant that small bands could expand into larger bands, and Sapiens could develop tighter and more sophisticated types of cooperation.

The gossip theory might sound like a joke, but numerous studies support it. Even today the vast majority of human communication whether in the form of emails, phone calls or newspaper columns is gossip. It comes so naturally to us that it seems as if our language evolved for this very purpose. Do you think that history professors chat about the reasons for the First World War when they meet for lunch, or that nuclear physicists spend their coffee breaks at scientific conferences talking about quarks? Sometimes. But more often, they gossip about the professor who caught her husband cheating, or the quarrel between the head of the department and the dean, or the rumours that a colleague used his research funds to buy a Lexus. Gossip usually focuses on wrongdoings. Rumour-mongers are the original fourth estate, journalists who inform society about and thus protect it from cheats and freeloaders.

Most likely, both the gossip theory and the there-is-a-lion-near-the-river theory are valid. Yet the truly unique feature of our language is not its ability to transmit information about men and lions. Rather, it’s the ability to transmit information about things that do not exist at all.

As far as we know, only Sapiens can talk about entire kinds of entities that they have never seen, touched or smelled.

Legends, myths, gods and religions appeared for the first time with the Cognitive Revolution. Many animals and human species could previously say, ‘Careful! A lion!’ Thanks to the Cognitive Revolution, Homo sapiens acquired the ability to say, ‘The lion is the guardian spirit of our tribe.’ This ability to speak about fictions is the most unique feature of Sapiens language.

It’s relatively easy to agree that only Homo sapiens can speak about things that don’t really exist, and believe six impossible things before breakfast. You could never convince a monkey to give you a banana by promising him limitless bananas after death in monkey heaven. But why is it important? After all, fiction can be dangerously misleading or distracting.

People who go to the forest looking for fairies and unicorns would seem to have less chance of survival than people who go looking for mushrooms and deer. And if you spend hours praying to non-existing guardian spirits, aren’t you wasting precious time, time better spent foraging, fighting and fornicating?

But fiction has enabled us not merely to imagine things, but to do so collectively. We can weave common myths such as the biblical creation story, the Dreamtime myths of Aboriginal Australians, and the nationalist myths of modern states. Such myths give Sapiens the unprecedented ability to cooperate flexibly in large numbers. Ants and bees can also work together in huge numbers, but they do so in a very rigid manner and only with close relatives. Wolves and chimpanzees cooperate far more flexibly than ants, but they can do so only with small numbers of other individuals that they know intimately.

Sapiens can cooperate in extremely flexible ways with countless numbers of strangers. That’s why Sapiens rule the world, whereas ants eat our leftovers and chimps are locked up in zoos and research laboratories.

The Legend of Peugeot

Our chimpanzee cousins usually live in small troops of several dozen individuals. They form close friendships, hunt together and fight shoulder to shoulder against baboons, Cheetahs and enemy chimpanzees. Their social structure tends to be hierarchical. The dominant member, who is almost always a male, is termed the ‘alpha male’. Other males and females exhibit their submission to the alpha male by bowing before him while making grunting sounds, not unlike human subjects kowtowing before a king. The alpha male strives to maintain social harmony within his troop. When two individuals fight, he will intervene and stop the violence. Less benevolently, he might monopolise particularly coveted foods and prevent lower-ranking males from mating with the females.

When two males are contesting the alpha position, they usually do so by forming extensive coalitions of supporters, both male and female, from within the group. Ties between coalition members are based on intimate daily contact hugging, touching, kissing, grooming and mutual favours. Just as human politicians on election campaigns go around shaking hands and kissing babies, so aspirants to the top position in a chimpanzee group spend much time hugging, back-slapping and kissing baby chimps. The alpha male usually wins his position not because he is physically stronger, but because he leads a large and stable coalition. These coalitions play a central part not only during overt struggles for the alpha position, but in almost all day-to-day activities. Members of a coalition spend more time together, share food, and help one another in times of trouble.

There are clear limits to the size of groups that can be formed and maintained in such a way. In order to function, all members of a group must know each other intimately. Two chimpanzees who have never met, never fought, and never engaged in mutual grooming will not know whether they can trust one another, whether it would be worthwhile to help one another, and which of them ranks higher. Under natural conditions, a typical chimpanzee troop consists of about twenty to fifty individuals. As the number of chimpanzees in a troop increases, the social order destabilises, eventually leading to a rupture and the formation of a new troop by some of the animals. Only in a handful of cases have zoologists observed groups larger than a hundred. Separate groups seldom cooperate, and tend to compete for territory and food. Researchers have documented prolonged warfare between groups, and even one case of ‘genocidal’ activity in which one troop systematically slaughtered most members of a neighbouring band.

Similar patterns probably dominated the social lives of early humans, including archaic Homo sapiens. Humans, like chimps, have social instincts that enabled our ancestors to form friendships and hierarchies, and to hunt or fight together. However, like the social instincts of chimps, those of humans were adapted only for small intimate groups. When the group grew too large, its social order destabilised and the band split. Even if a particularly fertile valley could feed 500 archaic Sapiens, there was no way that so many strangers could live together. How could they agree who should be leader, who should hunt where, or who should mate with whom?

In the wake of the Cognitive Revolution, gossip helped Homo sapiens to form larger and more stable bands. But even gossip has its limits. Sociological research has shown that the maximum ‘natural’ size of a group bonded by gossip is about 150 individuals. Most people can neither intimately know, nor gossip effectively about, more than 150 human beings.

Even today, a critical threshold in human organisations falls somewhere around this magic number. Below this threshold, communities, businesses, social networks and military units can maintain themselves based mainly on intimate acquaintance and rumour-mongering. There is no need for formal ranks, titles and law books to keep order. A platoon of thirty soldiers or even a company of a hundred soldiers can function well on the basis of intimate relations, with a minimum of formal discipline. A well-respected sergeant can become ‘king of the company’ and exercise authority even over commissioned officers. A small family business can survive and flourish without a board of directors, a CEO or an accounting department.

But once the threshold of 150 individuals is crossed, things can no longer work that way. You cannot run a division with thousands of soldiers the same way you run a platoon. Successful family businesses usually face a crisis when they grow larger and hire more personnel. If they cannot reinvent themselves, they go bust.

How did Homo sapiens manage to cross this critical threshold, eventually founding cities comprising tens of thousands of inhabitants and empires ruling hundreds of millions? The secret was probably the appearance of fiction. Large numbers of strangers can cooperate successfully by believing in common myths.

Any large-scale human cooperation whether a modern state, a medieval church, an ancient city or an archaic tribe is rooted in common myths that exist only in people’s collective imagination. Churches are rooted in common religious myths. Two Catholics who have never met can nevertheless go together on crusade or pool funds to build a hospital because they both believe that God was incarnated in human flesh and allowed Himself to be crucified to redeem our sins. States are rooted in common national myths. Two Serbs who have never met might risk their lives to save one another because both believe in the existence of the Serbian nation, the Serbian homeland and the Serbian flag. Judicial systems are rooted in common legal myths. Two lawyers who have never met can nevertheless combine efforts to defend a complete stranger because they both believe in the existence of laws, justice, human rights and the money paid out in fees.

Yet none of these things exists outside the stories that people invent and tell one another. There are no gods in the universe, no nations, no money, no human rights, no laws and no justice outside the common imagination of human beings.

People easily understand that ‘primitives’ cement their social order by believing in ghosts and spirits, and gathering each full moon to dance together around the campfire. What we fail to appreciate is that our modern institutions function on exactly the same basis. Take for example the world of business corporations. Modern businesspeople and lawyers are, in fact, powerful sorcerers. The principal difference between them and tribal shamans is that modern lawyers tell far stranger tales. The legend of Peugeot affords us a good example.

An icon that somewhat resembles the Stadel lion-man appears today on cars, trucks and motorcycles from Paris to Sydney. It’s the hood ornament that adorns vehicles made by Peugeot, one of the oldest and largest of Europe’s carmakers. Peugeot began as a small family business in the village of Valentigney, just 300 kilometres from the Stadel Cave. Today the company employs about 200,000 people worldwide, most of whom are complete strangers to each other. These strangers cooperate so effectively that in 2008 Peugeot produced more than 1.5 million automobiles, earning revenues of about 55 billion euros.

In what sense can we say that Peugeot SA (the company’s official name) exists? There are many Peugeot vehicles, but these are obviously not the company. Even if every Peugeot in the world were simultaneously junked and sold for scrap metal, Peugeot SA would not disappear. It would continue to manufacture new cars and issue its annual report. The company owns factories, machinery and showrooms, and employs mechanics, accountants and secretaries, but all these together do not comprise Peugeot. A disaster might kill every single one of Peugeot’s employees, and go on to destroy all of its assembly lines and executive offices. Even then, the company could borrow money, hire new employees, build new factories and buy new machinery. Peugeot has managers and shareholders, but neither do they constitute the company. All the managers could be dismissed and all its shares sold, but the company itself would remain intact.

It doesn’t mean that Peugeot SA is invulnerable or immortal. If a judge were to mandate the dissolution of the company, its factories would remain standing and its workers, accountants, managers and shareholders would continue to live but Peugeot SA would immediately vanish. In short, Peugeot SA seems to have no essential connection to the physical world. Does it really exist?

Peugeot is a figment of our collective imagination. Lawyers call this a ‘legal fiction’. It can’t be pointed at; it is not a physical object. But it exists as a legal entity. Just like you or me, it is bound by the laws of the countries in which it operates. It can open a bank account and own property. It pays taxes, and it can be sued and even prosecuted separately from any of the people who own or work for it.

Peugeot belongs to a particular genre of legal fictions called ‘limited liability companies’. The idea behind such companies is among humanity’s most ingenious inventions. Homo sapiens lived for untold millennia without them. During most of recorded history property could be owned only by flesh-and-blood humans, the kind that stood on two legs and had big brains. If in thirteenth-century France Jean set up a wagon-manufacturing workshop, he himself was the business. If a wagon he’d made broke down a week after purchase, the disgruntled buyer would have sued Jean personally. If Jean had borrowed 1,000 gold coins to set up his workshop and the business failed, he would have had to repay the loan by selling his private property his house, his cow, his land. He might even have had to sell his children into servitude. If he couldn’t cover the debt, he could be thrown in prison by the state or enslaved by his creditors. He was fully liable, without limit, for all obligations incurred by his workshop.

If you had lived back then, you would probably have thought twice before you opened an enterprise of your own. And indeed this legal situation discouraged entrepreneurship. People were afraid to start new businesses and take economic risks. It hardly seemed worth taking the chance that their families could end up utterly destitute.

This is why people began collectively to imagine the existence of limited liability companies. Such companies were legally independent of the people who set them up, or invested money in them, or managed them. Over the last few centuries such companies have become the main players in the economic arena, and we have grown so used to them that we forget they exist only in our imagination. In the US, the technical term for a limited liability company is a ‘corporation’, which is ironic, because the term derives from ‘corpus’ (‘body’ in Latin) the one thing these corporations lack. Despite their having no real bodies, the American legal system treats corporations as legal persons, as if they were flesh-and-blood human beings.

And so did the French legal system back in 1896, when Armand Peugeot, who had inherited from his parents a metalworking shop that produced springs, saws and bicycles, decided to go into the automobile business. To that end, he set up a limited liability company. He named the company after himself, but it was independent of him. If one of the cars broke down, the buyer could sue Peugeot, but not Armand Peugeot. If the company borrowed millions of francs and then went bust, Armand Peugeot did not owe its creditors a single franc. The loan, after all, had been given to Peugeot, the company, not to Armand Peugeot, the Homo sapiens. Armand Peugeot died in 1915. Peugeot, the company, is still alive and well.

How exactly did Armand Peugeot, the man, create Peugeot, the company? In much the same way that priests and sorcerers have created gods and demons throughout history, and in which thousands of French curés were still creating Christ’s body every Sunday in the parish churches. It all revolved around telling stories, and convincing people to believe them. In the case of the French curés, the crucial story was that of Christ’s life and death as told by the Catholic Church. According to this story, if a Catholic priest dressed in his sacred garments solemnly, said the right words at the right moment, mundane bread and wine turned into God’s flesh and blood. The priest exclaimed, ‘Hoc est corpus meum!’ (Latin for ‘This is my body!’) and hocus pocus the bread turned into Christ’s flesh. Seeing that the priest had properly and assiduously observed all the procedures, millions of devout French Catholics behaved as if God really existed in the consecrated bread and wine.

In the case of Peugeot SA the crucial story was the French legal code, as written by the French parliament. According to the French legislators, if a certified lawyer followed all the proper liturgy and rituals, wrote all the required spells and oaths on a wonderfully decorated piece of paper, and affixed his ornate signature to the bottom of the document, then hocus pocus a new company was incorporated. When in 1896 Armand Peugeot wanted to create his company, he paid a lawyer to go through all these sacred procedures. Once the lawyer had performed all the right rituals and pronounced all the necessary spells and oaths, millions of upright French citizens behaved as if the Peugeot company really existed.

Telling effective stories is not easy. The difficulty lies not in telling the story, but in convincing everyone else to believe it. Much of history revolves around this question: how does one convince millions of people to believe particular stories about gods, or nations, or limited liability companies? Yet when it succeeds, it gives Sapiens immense power, because it enables millions of strangers to cooperate and work towards common goals. Just try to imagine how difficult it would have been to create states, or churches, or legal systems if we could speak only about things that really exist, such as rivers, trees and lions.

Over the years, people have woven an incredibly complex network of stories. Within this network, fictions such as Peugeot not only exist, but also accumulate immense power. The kinds of things that people create through this network of stories are known in academic circles as ‘fictions’, ‘social constructs’ or ‘imagined realities’. An imagined reality is not a lie. I lie when I say that there is a lion near the river when I know perfectly well that there is no lion there. There is nothing special about lies. Green monkeys and chimpanzees can lie. A green monkey, for example, has been observed calling ‘Careful! A lion!’ when there was no lion around. This alarm conveniently frightened away a fellow monkey who had just found a banana, leaving the liar all alone to steal the prize for itself.

Unlike lying, an imagined reality is something that everyone believes in, and as long as this communal belief persists, the imagined reality exerts force in the world. The sculptor from the Stadel Cave may sincerely have believed in the existence of the lion-man guardian spirit. Some sorcerers are Charlatans, but most sincerely believe in the existence of gods and demons. Most millionaires sincerely believe in the existence of money and limited liability companies. Most human-rights activists sincerely believe in the existence of human rights. No one was lying when, in 2011, the UN demanded that the Libyan government respect the human rights of its citizens, even though the UN, Libya and human rights are all figments of our fertile imaginations.

Ever since the Cognitive Revolution, Sapiens have thus been living in a dual reality. On the one hand, the objective reality of rivers, trees and lions; and on the other hand, the imagined reality of gods, nations and corporations. As time went by, the imagined reality became ever more powerful, so that today the very survival of rivers, trees and lions depends on the grace of imagined entities such as the United States and Google.

Bypassing the Genome

The ability to create an imagined reality out of words enabled large numbers of strangers to cooperate effectively. But it also did something more. Since large-scale human cooperation is based on myths, the way people cooperate can be altered by changing the myths, by telling different stories. Under the right circumstances myths can change rapidly. In 1789 the French population switched almost overnight from believing in the myth of the divine right of kings to believing in the myth of the sovereignty of the people.

Consequently, ever since the Cognitive Revolution Homo sapiens has been able to revise its behaviour rapidly in accordance with changing needs. This opened a fast lane of cultural evolution, bypassing the traffic jams of genetic evolution. Speeding down this fast lane, Homo sapiens soon far outstripped all other human and animal species in its ability to cooperate.

The behaviour of other social animals is determined to a large extent by their genes. DNA is not an autocrat. Animal behaviour is also influenced by environmental factors and individual quirks. Nevertheless, in a given environment, animals of the same species will tend to behave in a similar way. Significant changes in social behaviour cannot occur, in general, without genetic mutations. For example, common chimpanzees have a genetic tendency to live in hierarchical groups headed by an alpha male. Members of a closely related chimpanzee species, bonobos, usually live in more egalitarian groups dominated by female alliances. Female common chimpanzees cannot take lessons from their bonobo relatives and stage a feminist revolution. Male chimps cannot gather in a constitutional assembly to abolish the office of alpha male and declare that from here on out all chimps are to be treated as equals. Such dramatic changes in behaviour would occur only if something changed in the chimpanzees’ DNA.

For similar reasons, archaic humans did not initiate any revolutions. As far as we can tell, changes in social patterns, the invention of new technologies and the settlement of alien habitats resulted from genetic mutations and environmental pressures more than from cultural initiatives. This is why it took humans hundreds of thousands of years to make these steps. Two million years ago, genetic mutations resulted in the appearance of a new human species called Homo erectus. Its emergence was accompanied by the development of a new stone tool technology, now recognised as a defining feature of this species. As long as Homo erectus did not undergo further genetic alterations, its stone tools remained roughly the same for close to 2 million years!

In contrast, ever since the Cognitive Revolution, Sapiens have been able to change their behaviour quickly, transmitting new behaviours to future generations without any need of genetic or environmental change. As a prime example, consider the repeated appearance of childless elites, such as the Catholic priesthood, Buddhist monastic orders and Chinese eunuch bureaucracies. The existence of such elites goes against the most fundamental principles of natural selection, since these dominant members of society willingly give up procreation. Whereas chimpanzee alpha males use their power to have sex with as many females as possible and consequently sire a large proportion of their troop’s young the Catholic alpha male abstains completely from sexual intercourse and childcare. This abstinence does not result from unique environmental conditions such as a severe lack of food or want of potential mates. Nor is it the result of some quirky genetic mutation. The Catholic Church has survived for centuries, not by passing on a ‘celibacy gene’ from one pope to the next, but by passing on the stories of the New Testament and of Catholic canon law.

In other words, while the behaviour patterns of archaic humans remained fixed for tens of thousands of years, Sapiens could transform their social structures, the nature of their interpersonal relations, their economic activities and a host of other behaviours within a decade or two. Consider a resident of Berlin, born in 1900 and living to the ripe age of one hundred. She spent her childhood in the Hohenzollern Empire of Wilhelm ll; her adult years in the Weimar Republic, the Nazi Third Reich and Communist East Germany; and she died a citizen of a democratic and reunified Germany. She had managed to be a part of five very different sociopolitical systems, though her DNA remained exactly the same.

This was the key to Sapiens’ success. In a one-on-one brawl, a Neanderthal would probably have beaten a Sapiens. But in a conflict of hundreds, Neanderthals wouldn’t stand a chance. Neanderthals could share information about the whereabouts of lions, but they probably could not tell and revise stories about tribal spirits. Without an ability to compose fiction, Neanderthals were unable to cooperate effectively in large numbers, nor could they adapt their social behaviour to rapidly changing challenges.

While we can’t get inside a Neanderthal mind to understand how they thought, we have indirect evidence of the limits to their cognition compared with their Sapiens rivals. Archaeologists excavating 30,000 year old Sapiens sites in the European heartland occasionally find there seashells from the Mediterranean and Atlantic coasts. In all likelihood, these shells got to the continental interior through long distance trade between different Sapiens bands. Neanderthal sites lack any evidence of such trade. Each group manufactured its own tools from local materials.

Another example comes from the South Pacific. Sapiens bands that lived on the island of New Ireland, north of New Guinea, used a volcanic glass called obsidian to manufacture particularly strong and sharp tools. New Ireland, however, has no natural deposits of obsidian. Laboratory tests revealed that the obsidian they used was brought from deposits on New Britain, an island 400 kilometres away. Some of the inhabitants of these islands must have been skilled navigators who traded from island to island over long distances.

Trade may seem a very pragmatic activity, one that needs no fictive basis. Yet the fact is that no animal other than Sapiens engages in trade, and all the Sapiens trade networks about which we have detailed evidence were based on fictions. Trade cannot exist without trust, and it is very difficult to trust strangers. The global trade network of today is based on our trust in such fictional entities as the dollar, the Federal Reserve Bank, and the totemic trademarks of corporations. When two strangers in a tribal society want to trade, they will often establish trust by appealing to a common god, mythical ancestor or totem animal.

If archaic Sapiens believing in such fictions traded shells and obsidian, it stands to reason that they could also have traded information, thus creating a much denser and wider knowledge network than the one that served Neanderthals and other archaic humans.

Hunting techniques provide another illustration of these differences. Neanderthals usually hunted alone or in small groups. Sapiens, on the other hand, developed techniques that relied on cooperation between many dozens of individuals, and perhaps even between different bands. One particularly effective method was to surround an entire herd of animals, such as wild horses, then chase them into a narrow gorge, where it was easy to slaughter them en masse. If all went according to plan, the bands could harvest tons of meat, fat and animal skins in a single afternoon of collective effort, and either consume these riches in a giant potlatch, or dry, smoke or (in Arctic areas) freeze them for later usage. Archaeologists have discovered sites where entire herds were butchered annually in such ways. There are even sites where fences and obstacles were erected in order to create artificial traps and slaughtering grounds.

We may presume that Neanderthals were not pleased to see their traditional hunting grounds turned into Sapiens controlled slaughterhouses. However, if violence broke out between the two species, Neanderthals were not much better off than wild horses. Fifty Neanderthals cooperating in traditional and static patterns were no match for 500 versatile and innovative Sapiens. And even if the Sapiens lost the first round, they could quickly invent new stratagems that would enable them to win the next time.

What happened in the Cognitive Revolution?

The immense diversity of imagined realities that Sapiens invented, and the resulting diversity of behaviour patterns, are the main components of what we call ‘cultures’. Once cultures appeared, they never ceased to change and develop, and these unstoppable alterations are what we call ‘history’.

The Cognitive Revolution is accordingly the point when history declared its independence from biology. Until the Cognitive Revolution, the doings of all human species belonged to the realm of biology, or, if you so prefer, prehistory (I tend to avoid the term ‘prehistory’, because it wrongly implies that even before the Cognitive Revolution, humans were in a category of their own). From the Cognitive Revolution onwards, historical narratives replace biological theories as our primary means of explaining the development of Homo sapiens. To understand the rise of Christianity or the French Revolution, it is not enough to comprehend the interaction of genes, hormones and organisms. It is necessary to take into account the interaction of ideas, images and fantasies as well.

This does not mean that Homo sapiens and human culture became exempt from biological laws. We are still animals, and our physical, emotional and cognitive abilities are still shaped by our DNA. Our societies are built from the same building blocks as Neanderthal or chimpanzee societies, and the more we examine these building blocks, sensations, emotions, family ties, the less difference we find between us and other apes.

It is, however, a mistake to look for the differences at the level of the individual or the family. One on one, even ten on ten, we are embarrassingly similar to chimpanzees. Significant differences begin to appear only when we cross the threshold of 150 individuals, and when we reach 1,000-2,000 individuals, the differences are astounding. If you tried to bunch together thousands of chimpanzees into Tiananmen Square, Wall Street, the Vatican or the headquarters of the United Nations, the result would be pandemonium. By contrast, Sapiens regularly gather by the thousands in such places. Together, they create orderly patterns such as trade networks, mass celebrations and political institutions that they could never have created in isolation. The real difference between us and chimpanzees is the mythical glue that binds together large numbers of individuals, families and groups. This glue has made us the masters of creation.

Of course, we also needed other skills, such as the ability to make and use tools. Yet tool-making is of little consequence unless it is coupled with the ability to cooperate with many others. How is it that we now have intercontinental missiles with nuclear warheads, whereas 30,000 years ago we had only sticks with flint spearheads? Physiologically, there has been no significant improvement in our tool-making capacity over the last 30,000 years. Albert Einstein was far less dexterous with his hands than was an ancient hunter-gatherer. However, our capacity to cooperate with large numbers of strangers has improved dramatically. The ancient flint spearhead was manufactured in minutes by a single person, who relied on the advice and help of a few intimate friends. The production of a modern nuclear warhead requires the cooperation of millions of strangers all over the world from the workers who mine the uranium ore in the depths of the earth to theoretical physicists who write long mathematical formulae to describe the interactions of subatomic particles.

To summarise the relationship between biology and history after the Cognitive Revolution:

1. Biology sets the basic parameters for the behaviour and capacities of Homo sapiens. The whole of history takes place within the bounds of this biological arena.

2. However, this arena is extraordinarily large, allowing Sapiens to play an astounding variety of games. Thanks to their ability to invent fiction, Sapiens create more and more complex games, which each generation develops and elaborates even further.

3. Consequently, in order to understand how Sapiens behave, we must describe the historical evolution of their actions. Referring only to our biological constraints would be like a radio sportscaster who, attending the World Cup football championships, offers his listeners a detailed description of the playing field rather than an account of what the players are doing.

What games did our Stone Age ancestors play in the arena of history? As far as we know, the people who carved the Stadel lion-man some 30,000 years ago had the same physical, emotional and intellectual abilities we have. What did they do when they woke up in the morning? What did they eat for breakfast and lunch? What were their societies like? Did they have monogamous relationships and nuclear families? Did they have ceremonies, moral codes, sports contests and religious rituals? Did they fight wars? The next chapter takes a peek behind the curtain of the ages, examining what life was like in the millennia separating the Cognitive Revolution from the Agricultural Revolution.

3. A Day in the Life of Adam and Eve

TO UNDERSTAND OUR nature, history and psychology, we must get inside the heads of our hunter-gatherer ancestors. For nearly the entire history of our species, Sapiens lived as foragers. The past 200 years, during which ever increasing numbers of Sapiens have obtained their daily bread as urban labourers and office workers, and the preceding 10,000 years, during which most Sapiens lived as farmers and herders, are the blink of an eye compared to the tens of thousands of years during which our ancestors hunted and gathered.

The flourishing field of evolutionary psychology argues that many of our present-day social and psychological characteristics were shaped during this long preagricultural era. Even today, scholars in this field claim, our brains and minds are adapted to a life of hunting and gathering. Our eating habits, our conflicts and our sexuality are all the result of the way our hunter-gatherer minds interact with our current post-industrial environment, with its mega-cities, aeroplanes, telephones and computers. This environment gives us more material resources and longer lives than those enjoyed by any previous generation, but it often makes us feel alienated, depressed and pressured.

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from

Sapiens, A Brief History of Humankind

by Yuval Noah Harari

get it at Amazon.com

How Our Brains Grow – Ruby Wax.

Evolution plays its part in creating an experience dependent brain in that you are born inside out (don’t panic it all works out) so when you’re only a one month old embryo, your outer layer of cells folds inward forming your brain stem and this is why our insides were once literally connected to the outside. The DNA instructs the neurons on which area they should migrate to. They then connect to each other, based on your experience and that ultimately will determine how your brain is shaped.

Only the strong and often used neurons survive and the rest die off, like sperm that don’t make it through the big swim.

Somehow every single cell has to know if it’s a cell for your nose or part of your toenail and find its way to that particular area. No satnav, no nothing. Can you imagine that kind of a challenge? Trillions of cells trying to put together the puzzle of all your parts; what makes you you. It would be like rush hour, squared.

What are the chances that you come out vaguely normal and not looking like a Picasso with three breasts coming out of your forehead? I wouldn’t bet on the odds. And let’s say you form the full complement of limbs and digits and a brain that works, now you depend on your parents, two descendants of a one-celled amoeba, to fill your tiny empty brain with the first spoonfuls of knowledge; teaching you to talk, walk, think, feel, flirt and freak out. This is why each of us, each generation, has to struggle with this universal quandary: what are we supposed to be doing here?

Reptiles lay some eggs or just stand and deliver and move on; without sentimentality they walk away to mate again somewhere with anyone who happens to be mounting them at the time while they’re munching on some lawn. Then the baby automatically knows how to swim, slither, trot or fly away. We are born knowing nothing and just lie there in our own mess till someone lifts us out of it and bothers to change our pants.

They, animals, need no manual, they just know things. Compared to other primates, humans are born far too early for their brain to be mature, if we could stay in our mother’s womb for the brain to fully develop we’d be in there 24 months. The only reason we come out at nine months is because our heads wouldn’t fit through the birth canal if we stayed in there and would end up doing some serious damage to Mommy; she would probably never walk again and sue us for personal injury. You know that scene in Ben Hur where they tie each of a man’s legs to an elephant and then scream, ‘Giddy up’? That’s how Mommy would feel.

The genes build the scaffolding of your head invitro but once outside Baby only has his basic amphibian brain, just enough to keep his heart and breathing going and that’s about all. But it’s not all bad news, evolution can be smart sometimes and because we come out so undercooked the development of our brain depends on external experience. We have so much to learn once we’re out so we need that external stimuli to develop, which is a blessing because it would be impossible to learn shorthand or ping pong while we’re inside the womb.

This is a very clever idea because no one knows where you’re going to be born and you need different skills depending on the area and culture you plop out into. If you’re born in the Sahara, it would be good to have a structure that would make you proficient in camel straddling or if you’re born in New York, it’s more helpful if you develop the motor skills to honk and scream at other drivers. We have so much learning to do. This is called neural Darwinism.

By age three, the baby’s brain has formed about 1000 trillion synaptic connections.

At that point, the baby has the equipment to speak any language in the world. Its ears, tongue and mouth are primed for any sound or accent that may be needed depending on where it’s born. The sounds around you shape your tongue and palate, so the first 16 months will determine your accent. If you are Chinese, you will probably leave out ‘r’s for the rest of your life. ‘I’m sowwy but it’s twoo’. If you’re German, you will probably make that sound in your throat that sounds like you’re about to bring up phlegm.

Before you learn to speak, your brain is like a wad of chewing gum so any language is possible to learn with the perfect accompanying accent and, unless you become an impressionist, you’ll be stuck with it.

You better learn fast at this point because after the first two months half your neurons drop dead.

The right hemisphere has a higher rate of growth during the first 18 months, which establish the basic structures of attachment and emotional regulation. During the second year of life, a growth spurt happens in the left hemisphere. We learn to crawl, then walk and then there’s an explosion of language skills such as saying ‘poo, poo’. The hands and eyes become more connected to visual stimuli and vocabulary develops, so now we can demand things like a rattle on ice with a splash of vermouth. The language areas are activated by about 18 months after birth and babies begin to develop selfconsciousness where they can recognize themselves in a mirror.

This is the birth of the concept of ‘I’ when you get that feeling that you are you, if you know what I mean.

As Baby matures, neural circuits guided by the environment, connect. As sensory systems develop, they provide increasingly precise input to shape neural network formation and more and more complex patterns of behaviour. Now Baby can draw like Rembrandt. Movements and emotional networks connect with motor systems so you can spit in someone’s face because they have pissed you off.

Now all the wires of behaviour, movement, sensory experience and emotions connect and feed each other information, like wires in a complex phone system. Right and left hemisphere integration allows us to put feelings into words. This linking up of right and left hemispheres is accomplished through Mommy and Baby eye contact, facial expressions and speaking ‘goo goo’ which is called ‘motherese’. (Some lesbians use it with their cats.) The baby imitates Mommy and so she/he learns how to put feelings into words. Then when Mommy rocks the baby, her hormones are released making baby feel safe. A game of peekaboo activates the baby’s nervous system by the fine art of surprise and leads to cascades of biological processes enhancing Baby’s excitement. Peek-a-boo is not just an aimless activity, it is a brain grower. So forget chess and suduko, just jump out at someone from behind a door, you’ll be doing them a big favour, upping their IQ by thousands.

The memory of how Mommy is with Baby influences the baby’s physiology, biology, neurology and psychology. How the brain grows is affected by how she put you down, held, smiled, ignored or forgot you; she is the uber-regulator, the big boss of brain development. The neural clusters for social and emotional learning are sculpted by Mommy’s attunement with Baby.

She grows these neurons in the baby by making direct eye contact with her left eye to Baby’s right eye. This is why Mommies usually hold babies in their left arm so this eye contact is made easier.

When they gaze into each others’ eyes, their hearts, brains and minds are linking up. These face-to-face interactions increase oxygen consumption and energy. Also holding the baby in this position means it can hear Mommy’s heartbeat. Seeing her loving face looking down on Baby triggers high levels of endogenous opiates so he experiences pleasure in later social interactions by the positive and exciting stimulation from Mommy.

If the mother is too connected, this affects Baby and later he might feel people are encroaching on his space. If, on the other hand, she is too disconnected, he might in later life feel abandoned and become a comedian looking for constant attention. If the mother soothes the terrified baby, he learns to regulate his own fear. The mother’s face shows him what is safe and what isn’t. If she shows fear or any negative state, the baby internalizes it. If she expresses depression or shows an expressionless face, the baby, not being able to think something is wrong with the mother, believes he is the cause and so has a greater chance of having depression or some other mental dysfunction himself, while keeping an idealized image of his caretaker; his survival depends on her.

Babies are built to engage and respond to the world. If they don’t get a response, they stop engaging with the world and can become emotionally frozen.

The holding and separating which are repeated by mother and child, help baby to self-regulate throughout his life while he learns how to care for himself. When the mother over-holds you can soon see the results; every Jewish boy’s first novel is about mothers who never let go.

Neuroplasticity

It was thought about ten years ago that, genewise, you’re hard-wired from birth; imprisoned by your DNA. But now science has broken that shackle; change is possible well into old age. It was thanks to a scientist named Michael Meaney that the idea of genetic determinism was toppled like the Berlin Wall; here one day, gone the next. His experiments on rats showed that the way a mother treats her babies determines which genes in the offspring’s brains are turned on and which are turned off, demonstrating that the genes we’re born with are simply nature’s opening shot. The genes that make you shy, resilient, anxious, exuberant are shaped by maternal behaviour. If maternal behaviour changes, the genes change. Fearful baby rats were put with nurturing mother rats and were licked rather than ignored and their actual genetic expression changed, proving we’re not held captive by our genes.

I wouldn’t have wanted my mother to lick me but perhaps it would have made me more positive and loving. Who am I to say?

But the point is that the brain changes continuously by every sight, sound, taste, touch, thought, feeling etc. Experience and learning remodel new circuits, neurogenesis.

We do know some of our ingredients and what they do and maybe in years to come we’ll be able to carry around some kind of recipe where we can change who we are day by day. We might decide we want to take a tablespoon of oxytocin and dribble in some dopamine to make us feel good about finishing our homework.

But for right now, the practice of mindfulness gives you some of the utensils that help you turn something you burnt and destroyed into something that tastes good and feels soothing inside.

How misguided we are in insisting the external world is exactly as we see it. Much of what you see out there is manufactured by your brain, painted in like computer generated graphics in a movie; only a very small part of the inputs to your occipital lobe comes directly from the external world, the rest comes from internal memory stores and other processes.

Think of the area in your visual cortex, a projection room creating what’s out there from incoming information. In actuality we see the world in single snapshots and it is a part of your brain that makes it seem like it’s constantly moving. There are about 70 separate areas working to create a cohesive picture of the world; one part contributes colour, another movement, another edges, another picks up shapes and another shadows. There is no single part that gets the whole picture. And in completely different zones, the images get a name, or an association or an emotional tag.

We live in a virtual reality. Think of The Wizard of OZ, you’re being run by the guy behind the curtain. You get clips that randomly come into your consciousness, never the whole film. So while you’re getting these fleeting clips to make you feel that’s all that’s going on, a trillion things without you knowing it are going on right now inside of you.

When you wake up in the morning, you remember who you were the day before because of billions of neurons, electrically zapping around the brain, working around the clock to make you believe you have unity and keep you wanting to exist.

Another thing your remarkable brain is doing is keeping your heart beating more than 100,000 times per day, that’s 40 million heartbeats per year, pumping two gallons of blood per minute, through a system of vascular channels about 60,000 miles in length or twice the circumference of the Earth.

Just now 100,000 chemical reactions took place in every single one of your cells. Multiply 100,000 chemical reactions by the 70 to 100 trillion cells that make up you. (I couldn’t do that but maybe you can.) So while your bodies doing its ‘thing’ you could be using your mind to bring you calm and happiness. What a segue to introduce you to mindfulness.

Evolutionary Psychology

What Is Evolutionary Psychology?

Our bodies evolved over eons, slowly calibrating to the African savanna on which 98 percent of our ancestors lived and died. So, too, did our brains. Evolutionary psychology postulates that the mind is shaped by pressure to survive and reproduce.

We jealously guard romantic partners and cherish our closest relatives above all others, lest we fail to pass on our genes.

We easily acquire language, which is critical for cooperation and hence survival. Evolutionary psychology acknowledges these forces but stresses the ultimate (and largely unconscious) gene’s eye view of behavior.

Psychology Today

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Evolutionary psychology is a theoretical approach in the social and natural sciences that examines psychological structure from a modern evolutionary perspective. It seeks to identify which human psychological traits are evolved adaptations – that is, the functional products of natural selection or sexual selection in human evolution. Adaptationist thinking about physiological mechanisms, such as the heart, lungs, and immune system, is common in evolutionary biology. Some evolutionary psychologists apply the same thinking to psychology, arguing that the modularity of mind is similar to that of the body and with different modular adaptations serving different functions. Evolutionary psychologists argue that much of human behavior is the output of psychological adaptations that evolved to solve recurrent problems in human ancestral environments.

Evolutionary psychologists suggest that it is not simply a subdiscipline of psychology but that evolutionary theory can provide a foundational, metatheoretical framework that integrates the entire field of psychology in the same way evolution has for biology.

Evolutionary psychologists hold that behaviors or traits that occur universally in all cultures are good candidates for evolutionary adaptations including the abilities to infer others’ emotions, discern kin from non-kin, identify and prefer healthier mates, and cooperate with others. They report successful tests of theoretical predictions related to such topics as infanticide, intelligence, marriage patterns, promiscuity, perception of beauty, bride price, and parental investment.

The theories and findings of evolutionary psychology have applications in many fields, including economics, environment, health, law, management, psychiatry, politics, and literature.

Criticism of evolutionary psychology involves questions of testability, cognitive and evolutionary assumptions (such as modular functioning of the brain, and large uncertainty about the ancestral environment), importance of non-genetic and non-adaptive explanations, as well as political and ethical issues due to interpretations of research results.

Principles

Evolutionary psychology is an approach that views human nature as the product of a universal set of evolved psychological adaptations to recurring problems in the ancestral environment. Proponents suggest that it seeks to integrate psychology into the other natural sciences, rooting it in the organizing theory of biology (evolutionary theory), and thus understanding psychology as a branch of biology. Anthropologist John Tooby and psychologist Leda Cosmides note:

“Evolutionary psychology is the long-forestalled scientific attempt to assemble out of the disjointed, fragmentary, and mutually contradictory human disciplines a single, logically integrated research framework for the psychological, social, and behavioral sciences – a framework that not only incorporates the evolutionary sciences on a full and equal basis, but that systematically works out all of the revisions in existing belief and research practice that such a synthesis requires.”

Just as human physiology and evolutionary physiology have worked to identify physical adaptations of the body that represent “human physiological nature,” the purpose of evolutionary psychology is to identify evolved emotional and cognitive adaptations that represent “human psychological nature.” According to Steven Pinker, it is “not a single theory but a large set of hypotheses” and a term that “has also come to refer to a particular way of applying evolutionary theory to the mind, with an emphasis on adaptation, gene-level selection, and modularity.” Evolutionary psychology adopts an understanding of the mind that is based on the computational theory of mind. It describes mental processes as computational operations, so that, for example, a fear response is described as arising from a neurological computation that inputs the perceptional data, e.g. a visual image of a spider, and outputs the appropriate reaction, e.g. fear of possibly dangerous animals.

While philosophers have generally considered the human mind to include broad faculties, such as reason and lust, evolutionary psychologists describe evolved psychological mechanisms as narrowly focused to deal with specific issues, such as catching cheaters or choosing mates. The discipline views the human brain as comprising many functional mechanisms, called psychological adaptations or evolved cognitive mechanisms or cognitive modules, designed by the process of natural selection. Examples include language-acquisition modules, incest-avoidance mechanisms, cheater-detection mechanisms, intelligence and sex-specific mating preferences, foraging mechanisms, alliance-tracking mechanisms, agent-detection mechanisms, and others. Some mechanisms, termed domain-specific, deal with recurrent adaptive problems over the course of human evolutionary history. Domain-general mechanisms, on the other hand, are proposed to deal with evolutionary novelty.

Evolutionary psychology has roots in cognitive psychology and evolutionary biology but also draws on behavioral ecology, artificial intelligence, genetics, ethology, anthropology, archaeology, biology, and zoology. It is closely linked to sociobiology, but there are key differences between them including the emphasis on domain-specific rather than domain-general mechanisms, the relevance of measures of current fitness, the importance of mismatch theory, and psychology rather than behavior. Most of what is now labeled as sociobiological research is now confined to the field of behavioral ecology.

Nikolaas Tinbergen’s four categories of questions can help to clarify the distinctions between several different, but complementary, types of explanations. Evolutionary psychology focuses primarily on the “why?” questions, while traditional psychology focuses on the “how?” questions.

Premises

Evolutionary psychology is founded on several core premises.

The brain is an information processing device, and it produces behavior in response to external and internal inputs.
The brain’s adaptive mechanisms were shaped by natural and sexual selection.
Different neural mechanisms are specialized for solving problems in humanity’s evolutionary past.

The brain has evolved specialized neural mechanisms that were designed for solving problems that recurred over deep evolutionary time, giving modern humans stone-age minds. This is now being challenged by Cecilia Heyes.
Most contents and processes of the brain are unconscious; and most mental problems that seem easy to solve are actually extremely difficult problems that are solved unconsciously by complicated neural mechanisms.

Human psychology consists of many specialized mechanisms, each sensitive to different classes of information or inputs. These mechanisms combine to produce manifest behavior.

History of Evolutionary Psychology

The history of evolutionary psychology began with Charles Darwin, who said that humans have social instincts that evolved by natural selection.
Darwin’s work inspired later psychologists such as William James and Sigmund Freud but for most of the 20th century psychologists focused more on behaviorism and proximate explanations for human behavior.

E.O. Wilson’s landmark 1975 book, Sociobiology, synthesized recent theoretical advances in evolutionary theory to explain social behavior in animals, including humans.
Jerome Barkow, Leda Cosmides and John Tooby popularized the term “evolutionary psychology” in their 1992 book The Adapted Mind: Evolutionary Psychology and The Generation of Culture.

Like sociobiology before it, evolutionary psychology has been embroiled in controversy, but evolutionary psychologists see their field as gaining increased acceptance overall.

After his seminal work in developing theories of natural selection, Charles Darwin devoted much of his final years to the study of animal emotions and psychology.
He wrote two books; The Descent of Man, and Selection in Relation to Sex in 1871 and The Expression of the Emotions in Man and Animals in 1872 that dealt with topics related to evolutionary psychology.
He introduced the concepts of sexual selection to explain the presence of animal structures that seemed unrelated to survival, such as the peacock’s tail. He also introduced theories concerning group selection and kin selection to explain altruism.
Darwin pondered why humans and animals were often generous to their group members. Darwin felt that acts of generosity decreased the fitness of generous individuals. This fact contradicted natural selection which favored the fittest individual.
Darwin concluded that while generosity decreased the fitness of individuals, generosity would increase the fitness of a group. In this case, altruism arose due to competition between groups.

The following quote, from Darwin’s Origin of Species, is often interpreted by evolutionary psychologists as indication of his foreshadowing the emergence of the field:

“In the distant future I see open fields for far more important researches. Psychology will be based on a new foundation, that of the necessary acquirement of each mental power and capacity by gradation.”
Charles Darwin 1859
The Origin of Species, p.488

Darwin’s theory inspired William James’s functionalist approach to psychology. At the core of his theory was a system of “instincts.” James wrote that humans had many instincts, even more than other animals. These instincts, he said, could be overridden by experience and by each other, as many of the instincts were actually in conflict with each other.

In their Evolutionary Psychology Primer Tooby and Cosmides make note of James’ perspective, and also quote him:

“We do not realize that ‘normal’ behavior needs to be explained at all. This “instinct blindness” makes the study of psychology difficult. To get past this problem, James suggested that we try to make the “natural seem strange”:

William James “It takes…a mind debauched by learning to carry the process of making the natural seem strange, so far as to ask for the why of any instinctive human act. To the metaphysician alone can such questions occur as: Why do we smile, when pleased, and not scowl? Why are we unable to talk to a crowd as we talk to a single friend? Why does a particular maiden turn our wits so upside-down? The common man can only say, Of course we smile, of course our heart palpitates at the sight of the crowd, of course we love the maiden, that beautiful soul clad in that perfect form, so palpably and flagrantly made for all eternity to be loved!
And so, probably, does each animal feel about the particular things it tends to do in the presence of particular objects. … To the lion it is the lioness which is made to be loved; to the bear, the she-bear. To the broody hen the notion would probably seem monstrous that there should be a creature in the world to whom a nestful of eggs was not the utterly fascinating and precious and never-to-be-too-much-sat-upon object which it is to her.
Thus we may be sure that, however mysterious some animals’ instincts may appear to us, our instincts will appear no less mysterious to them. (William James, 1890)”

“In our view, William James was right about evolutionary psychology. Making the natural seem strange is unnatural — it requires the twisted outlook seen, for example, in Gary Larson cartoons. Yet it is a pivotal part of the enterprise. Many psychologists avoid the study of natural competences, thinking that there is nothing there to be explained.”

According to Noam Chomsky, perhaps Anarchist thinker Peter Kropotkin could be credited as having founded evolutionary psychology, when in his 1902 book Mutual Aid: A Factor of Evolution he argued that the human instinct for cooperation and mutual aid could be seen as stemming from evolutionary adaption.

William McDougall made a reference to “evolutionary psychology” in his 1919 book An Introduction to Social Psychology: “It is only a comparative and evolutionary psychology that can provide the needed basis (for psychology); and this could not be created before the work of Darwin had convinced men of the continuity of human with animal evolution as regards all bodily characters, and had prepared the way for the quickly following recognition of the similar continuity of man’s mental evolution with that of the animal world.”

While Darwin’s theories on natural selection gained acceptance in the early part of the 20th century, his theories on evolutionary psychology were largely ignored. Only after the second world war, in the 1950s, did interest increase in the systematic study of animal behavior. It was during this period that the modern field of ethology emerged. Konrad Lorenz and Nikolaas Tinbergen were pioneers in developing the theoretical framework for ethology for which they would receive a Nobel prize in 1973.

Desmond Morris’s book The Naked Ape attempted to frame human behavior in the context of evolution, but his explanations failed to convince academics because they were based on a teleological (goal-oriented) understanding of evolution. For example, he said that the pair bond evolved so that men who were out hunting could trust that their mates back home were not having sex with other men.

Sociobiology

In 1975, E.O. Wilson built upon the works of Lorenz and Tinbergen by combining studies of animal behavior, social behavior and evolutionary theory in his book Sociobiology: The New Synthesis. Wilson included a chapter on human behavior. Wilson’s application of evolutionary analysis to human behavior caused bitter debate.

With the publication of Sociobiology, evolutionary thinking for the first time had an identifiable presence in the field of psychology. E.O. Wilson argues that the field of evolutionary psychology is essentially the same as “human sociobiology”.

Edward H. Hagen writes in The Handbook of Evolutionary Psychology that sociobiology is, despite the public controversy regarding the applications to humans, “one of the scientific triumphs of the twentieth century.” “Sociobiology is now part of the core research and curriculum of virtually all biology departments, and it is a foundation of the work of almost all field biologists” Sociobiological research on nonhuman organisms has increased dramatically and appears continuously in the world’s top scientific journals such as Nature and Science. The more general term behavioral ecology is commonly used as substitute for the term sociobiology in order to avoid the public controversy.

Modern use of the term “evolutionary psychology”

The term evolutionary psychology was used by American biologist Michael Ghiselin in a 1973 article published in the journal Science. Jerome Barkow, Leda Cosmides and John Tooby popularized the term “evolutionary psychology” in their 1992 book The Adapted Mind: Evolutionary Psychology and The Generation of Culture.

In contrast to sociobiology and behavioral ecology, evolutionary psychology emphasizes that organisms are “adaptation executors” rather than “fitness maximizers.” In other words, organisms have emotional, motivational and cognitive adaptations that generally increased inclusive fitness in the past but may not do so in the present. This distinction may explain some maladaptive behaviors that are the result of “fitness lags” between ancestral and modern environments. For example, our ancestrally developed desires for fat, sugar and salt often lead to health problems in modern environment where these are readily available in large quantities.

Also, in contrast to sociobiology and behavioral ecology (which mostly study non-human animal behavior), rather than focus primarily on overt behavior, EP attempts to identify underlying psychological adaptations (including emotional, motivational and cognitive mechanisms), and how these mechanisms interact with the developmental and current environmental influences to produce behavior.

Before 1990, introductory psychology textbooks scarcely mentioned Darwin. In the 1990s, evolutionary psychology was treated as a fringe theory, and evolutionary psychologists depicted themselves as an embattled minority. Coverage in psychology textbooks was largely hostile. According to evolutionary psychologists, current coverage in psychology textbooks is usually neutral or balanced.

The presence that evolutionary theory holds in psychology has been steadily increasing. According to its proponents, evolutionary psychology now occupies a central place in psychological science.

Theoretical foundations of evolutionary psychology

The theoretical foundations of evolutionary psychology are the general and specific scientific theories that explain the ultimate origins of psychological traits in terms of evolution. These theories originated with Charles Darwin’s work, including his speculations about the evolutionary origins of social instincts in humans. Modern evolutionary psychology, however, is possible only because of advances in evolutionary theory in the 20th century.

Evolutionary psychologists say that natural selection has provided humans with many psychological adaptations, in much the same way that it generated humans’ anatomical and physiological adaptations. As with adaptations in general, psychological adaptations are said to be specialized for the environment in which an organism evolved, the environment of evolutionary adaptedness, or EEA. Sexual selection provides organisms with adaptations related to mating. For male mammals, which have a relatively fast reproduction rate, sexual selection leads to adaptations that help them compete for females. For female mammals, with a relatively slow reproduction rate, sexual selection leads to choosiness, which helps females select higher quality mates. Charles Darwin described both natural selection and sexual selection, but he relied on group selection to explain the evolution of self-sacrificing behavior. Group selection is a weak explanation because in any group the less self-sacrificing animals will be more likely to survive and the group will become less self-sacrificing.

In 1964, William D. Hamilton proposed inclusive fitness theory, emphasizing a “gene’s-eye” view of evolution. Hamilton noted that individuals can increase the replication of their genes into the next generation by helping close relatives with whom they share genes survive and reproduce. According to “Hamilton’s rule”, a self-sacrificing behavior can evolve if it helps close relatives so much that it more than compensates for the individual animal’s sacrifice. Inclusive fitness theory resolved the issue of how “altruism” evolved. Other theories also help explain the evolution of altruistic behavior, including evolutionary game theory, tit-for-tat reciprocity, and generalized reciprocity. These theories not only help explain the development of altruistic behavior but also account for hostility toward cheaters (individuals that take advantage of others’ altruism).

Several mid-level evolutionary theories inform evolutionary psychology. The r/K selection theory proposes that some species prosper by having many offspring while others follow the strategy of having fewer offspring but investing much more in each one. Humans follow the second strategy. Parental investment theory explains how parents invest more or less in individual offspring based on how successful those offspring are likely to be, and thus how much they might improve the parents’ inclusive fitness. According to the Trivers-Willard hypothesis, parents in good conditions tend to invest more in sons (who are best able to take advantage of good conditions), while parents in poor conditions tend to invest more in daughters (who are best able to have successful offspring even in poor conditions). According to life history theory, animals evolve life histories to match their environments, determining details such as age at first reproduction and number of offspring. Dual inheritance theory posits that genes and human culture have interacted, with genes affecting the development of culture and culture, in turn, affecting human evolution on a genetic level (see also the Baldwin effect).

Critics of evolutionary psychology have sometimes challenged its theoretical underpinnings, saying that humans never developed powerful social instincts through natural selection and that the hypotheses of evolutionary psychologists are merely just-so-stories.

General Evolutionary Theory

Evolutionary psychology primarily uses the theories of natural selection, sexual selection, and inclusive fitness to explain the evolution of psychological adaptations.

Evolutionary psychology is sometimes seen not simply as a subdiscipline of psychology but as a metatheoretical framework in which the entire field of psychology can be examined.

Natural selection

Evolutionary psychologists consider Charles Darwin’s theory of natural selection to be important to an understanding of psychology. Natural selection occurs because individual organisms who are genetically better suited to the current environment leave more descendants, and their genes spread through the population, thus explaining why organisms fit their environments so closely. This process is slow and cumulative, with new traits layered over older traits. The advantages created by natural selection are known as adaptations. Evolutionary psychologists say that animals, just as they evolve physical adaptations, evolve psychological adaptations.

Evolutionary psychologists emphasize that natural selection mostly generates specialized adaptations, which are more efficient than general adaptations. They point out that natural selection operates slowly, and that adaptations are sometimes out of date when the environment changes rapidly. In the case of humans, evolutionary psychologists say that much of human nature was shaped during the stone age and may not match the contemporary environment.

Sexual selection

Sexual selection favors traits that provide mating advantages, such as the peacock’s tail, even if these same traits are usually hindrances. Evolutionary psychologists point out that, unlike natural selection, sexual selection typically leads to the evolution of sex differences. Sex differences typically make reproduction faster for one sex and slower for the other, in which case mates are relatively scarce for the faster sex. Sexual selection favors traits that increase the number of mates for the fast sex and the quality of mates for the slow sex. For mammals, the female has the slower reproduction rate. Males typically evolve either traits to help them fight other males or traits to impress females. Females typically evolve greater abilities to discern the qualities of males, such as choosiness in mating.

Inclusive fitness

Inclusive fitness theory, proposed by William D. Hamilton, emphasized a “gene’s-eye” view of evolution. Hamilton noted that what evolution ultimately selects are genes, not groups or species. From this perspective, individuals can increase the replication of their genes into the next generation not only directly via reproduction, by also indirectly helping close relatives with whom they share genes survive and reproduce. General evolutionary theory, in its modern form, is essentially inclusive fitness theory.

Inclusive fitness theory resolved the issue of how “altruism” evolved. The dominant, pre-Hamiltonian view was that altruism evolved via group selection: the notion that altruism evolved for the benefit of the group. The problem with this was that if one organism in a group incurred any fitness costs on itself for the benefit of others in the group, (i.e. acted “altruistically”), then that organism would reduce its own ability to survive and/or reproduce, therefore reducing its chances of passing on its altruistic traits.

Furthermore, the organism that benefited from that altruistic act and only acted on behalf of its own fitness would increase its own chance of survival and/or reproduction, thus increasing its chances of passing on its “selfish” traits. Inclusive fitness resolved “the problem of altruism” by demonstrating that altruism can evolve via kin selection as expressed in Hamilton’s rule:

cost < relatedness × benefit

In other words, altruism can evolve as long as the fitness cost of the altruistic act on the part of the actor is less than the degree of genetic relatedness of the recipient times the fitness benefit to that recipient. This perspective reflects what is referred to as the gene-centered view of evolution and demonstrates that group selection is a very weak selective force.

Middle-level evolutionary theories

Middle-level evolutionary theories are consistent with general evolutionary theory, but focus on certain domains of functioning (Buss, 2011) Specific evolutionary psychology hypotheses may be derivative from a mid-level theory (Buss, 2011). Three very important middle-level evolutionary theories were contributed by Robert Trivers as well as Robert MacArthur and E. O. Wilson

The theory of parent-offspring conflict rests on the fact that even though a parent and his/her offspring are 50% genetically related, they are also 50% genetically different. All things being equal, a parent would want to allocate their resources equally amongst their offspring, while each offspring may want a little more for themselves. Furthermore, an offspring may want a little more resources from the parent than the parent is willing to give. In essence, parent-offspring conflict refers to a conflict of adaptive interests between parent and offspring. However, if all things are not equal, a parent may engage in discriminative investment towards one sex or the other, depending on the parent’s condition.

The Trivers–Willard hypothesis, which proposes that parents will invest more in the sex that gives them the greatest reproductive payoff (grandchildren) with increasing or marginal investment. Females are the heavier parental investors in our species. Because of that, females have a better chance of reproducing at least once in comparison to males, but males in good condition have a better chance of producing high numbers of offspring than do females in good condition. Thus, according to the Trivers–Willard hypothesis, parents in good condition are predicted to favor investment in sons, and parents in poor condition are predicted to favor investment in daughters.

r/K selection theory, which, in ecology, relates to the selection of traits in organisms that allow success in particular environments. r-selected species, i.e., species in unstable or unpredictable environments, produce many offspring, each of which is unlikely to survive to adulthood.
By contrast, K-selected species, i.e., species in stable or predictable environments, invest more heavily in fewer offspring, each of which has a better chance of surviving to adulthood.

Life history theory posits that the schedule and duration of key events in an organism’s lifetime are shaped by natural selection to produce the largest possible number of surviving offspring.
For any given individual, available resources in any particular environment are finite. Time, effort, and energy used for one purpose diminishes the time, effort, and energy available for another.
Examples of some major life history characteristics include: age at first reproductive event, reproductive lifespan and aging, and number and size of offspring.
Variations in these characteristics reflect different allocations of an individual’s resources (i.e., time, effort, and energy expenditure) to competing life functions.
For example, attachment theory proposes that caregiver attentiveness in early childhood can determine later adult attachment style. Also, Jay Belsky and others have found evidence that if the father is absent from the home, girls reach first menstruation earlier and also have more short term sexual relationships as women.

Evolved psychological mechanisms

Evolutionary psychology is based on the hypothesis that, just like hearts, lungs, livers, kidneys, and immune systems, cognition has functional structure that has a genetic basis, and therefore has evolved by natural selection.
Like other organs and tissues, this functional structure should be universally shared amongst a species, and should solve important problems of survival and reproduction.

Evolutionary psychologists seek to understand psychological mechanisms by understanding the survival and reproductive functions they might have served over the course of evolutionary history.
These might include abilities to infer others’ emotions, discern kin from non-kin, identify and prefer healthier mates, cooperate with others and follow leaders. Consistent with the theory of natural selection, evolutionary psychology sees humans as often in conflict with others, including mates and relatives.
For instance, a mother may wish to wean her offspring from breastfeeding earlier than does her infant, which frees up the mother to invest in additional offspring.
Evolutionary psychology also recognizes the role of kin selection and reciprocity in evolving prosocial traits such as altruism.
Like chimpanzees and bonobos, humans have subtle and flexible social instincts, allowing them to form extended families, lifelong friendships, and political alliances.
In studies testing theoretical predictions, evolutionary psychologists have made modest findings on topics such as infanticide, intelligence, marriage patterns, promiscuity, perception of beauty, bride price and parental investment.

Historical topics

Proponents of evolutionary psychology in the 1990s made some explorations in historical events, but the response from historical experts was highly negative and there has been little effort to continue that line of research.
Historian Lynn Hunt says that the historians complained that the researchers:

“have read the wrong studies, misinterpreted the results of experiments, or worse yet, turned to neuroscience looking for a universalizing, anti-representational and anti-intentional ontology to bolster their claims”

Hunt states that, “the few attempts to build up a subfield of psychohistory collapsed under the weight of its presuppositions.” She concludes that as of 2014 the “‘iron curtain’ between historians and psychology…remains standing.”

Products of evolution: adaptations, exaptations, byproducts, and random variation

Not all traits of organisms are evolutionary adaptations. As noted in the table below, traits may also be exaptations, byproducts of adaptations (sometimes called “spandrels”), or random variation between individuals.

Psychological adaptations are hypothesized to be innate or relatively easy to learn, and to manifest in cultures worldwide. For example, the ability of toddlers to learn a language with virtually no training is likely to be a psychological adaptation.
On the other hand, ancestral humans did not read or write, thus today, learning to read and write require extensive training, and presumably represent byproducts of cognitive processing that use psychological adaptations designed for other functions.
However, variations in manifest behavior can result from universal mechanisms interacting with different local environments. For example, Caucasians who move from a northern climate to the equator will have darker skin. The mechanisms regulating their pigmentation do not change; rather the input to those mechanisms change, resulting in different output.

One of the tasks of evolutionary psychology is to identify which psychological traits are likely to be adaptations, byproducts or random variation.
George C. Williams suggested that an “adaptation is a special and onerous concept that should only be used where it is really necessary.”
As noted by Williams and others, adaptations can be identified by their improbable complexity, species universality, and adaptive functionality.

Obligate and facultative adaptations

A question that may be asked about an adaptation is whether it is generally obligate (relatively robust in the face of typical environmental variation) or facultative (sensitive to typical environmental variation).
The sweet taste of sugar and the pain of hitting one’s knee against concrete are the result of fairly obligate psychological adaptations; typical environmental variability during development does not much affect their operation.
By contrast, facultative adaptations are somewhat like “if-then” statements. For example, adult attachment style seems particularly sensitive to early childhood experiences. As adults, the propensity to develop close, trusting bonds with others is dependent on whether early childhood caregivers could be trusted to provide reliable assistance and attention.
The adaptation for skin to tan is conditional to exposure to sunlight; this is an example of another facultative adaptation. When a psychological adaptation is facultative, evolutionary psychologists concern themselves with how developmental and environmental inputs influence the expression of the adaptation.

Cultural universals

Evolutionary psychologists hold that behaviors or traits that occur universally in all cultures are good candidates for evolutionary adaptations.[5] Cultural universals include behaviors related to language, cognition, social roles, gender roles, and technology.
Evolved psychological adaptations (such as the ability to learn a language) interact with cultural inputs to produce specific behaviors (e.g., the specific language learned).
Basic gender differences, such as greater eagerness for sex among men and greater coyness among women, are explained as sexually dimorphic psychological adaptations that reflect the different reproductive strategies of males and females.
Evolutionary psychologists contrast their approach to what they term the “standard social science model,” according to which the mind is a general-purpose cognition device shaped almost entirely by culture.

Environment of evolutionary adaptedness

Evolutionary psychology argues that to properly understand the functions of the brain, one must understand the properties of the environment in which the brain evolved. That environment is often referred to as the “environment of evolutionary adaptedness”.

The idea of an environment of evolutionary adaptedness was first explored as a part of attachment theory by John Bowlby.
This is the environment to which a particular evolved mechanism is adapted. More specifically, the environment of evolutionary adaptedness is defined as the set of historically recurring selection pressures that formed a given adaptation, as well as those aspects of the environment that were necessary for the proper development and functioning of the adaptation.

Humans, comprising the genus Homo, appeared between 1.5 and 2.5 million years ago, a time that roughly coincides with the start of the Pleistocene 2.6 million years ago. Because the Pleistocene ended a mere 12,000 years ago, most human adaptations either newly evolved during the Pleistocene, or were maintained by stabilizing selection during the Pleistocene. Evolutionary psychology therefore proposes that the majority of human psychological mechanisms are adapted to reproductive problems frequently encountered in Pleistocene environments.
In broad terms, these problems include those of growth, development, differentiation, maintenance, mating, parenting, and social relationships.

The environment of evolutionary adaptedness is significantly different from modern society.
The ancestors of modern humans lived in smaller groups, had more cohesive cultures, and had more stable and rich contexts for identity and meaning.
Researchers look to existing hunter-gatherer societies for clues as to how hunter-gatherers lived in the environment of evolutionary adaptedness.
Unfortunately, the few surviving hunter-gatherer societies are different from each other, and they have been pushed out of the best land and into harsh environments, so it is not clear how closely they reflect ancestral culture.

Evolutionary psychologists sometimes look to chimpanzees, bonobos, and other great apes for insight into human ancestral behavior. Christopher Ryan and Cacilda Jethá argue that evolutionary psychologists have overemphasized the similarity of humans and chimps, which are more violent, while underestimating the similarity of humans and bonobos, which are more peaceful.

Mismatches

Since an organism’s adaptations were suited to its ancestral environment, a new and different environment can create a mismatch. Because humans are mostly adapted to Pleistocene environments, psychological mechanisms sometimes exhibit “mismatches” to the modern environment.
One example is the fact that although about 10,000 people are killed with guns in the US annually, whereas spiders and snakes kill only a handful, people nonetheless learn to fear spiders and snakes about as easily as they do a pointed gun, and more easily than an unpointed gun, rabbits or flowers.
A potential explanation is that spiders and snakes were a threat to human ancestors throughout the Pleistocene, whereas guns (and rabbits and flowers) were not. There is thus a mismatch between humans’ evolved fear-learning psychology and the modern environment.

This mismatch also shows up in the phenomena of the supernormal stimulus, a stimulus that elicits a response more strongly than the stimulus for which the response evolved.
The term was coined by Niko Tinbergen to refer to non-human animal behavior, but psychologist Deirdre Barrett said that supernormal stimulation governs the behavior of humans as powerfully as that of other animals. She explained junk food as an exaggerated stimulus to cravings for salt, sugar, and fats, and she says that television is an exaggeration of social cues of laughter, smiling faces and attention-grabbing action.
Magazine centerfolds and double cheeseburgers pull instincts intended for an EEA where breast development was a sign of health, youth and fertility in a prospective mate, and fat was a rare and vital nutrient.
The psychologist Mark van Vugt recently argued that modern organizational leadership is a mismatch. His argument is that humans are not adapted to work in large, anonymous bureaucratic structures with formal hierarchies. The human mind still responds to personalized, charismatic leadership primarily in the context of informal, egalitarian settings. Hence the dissatisfaction and alienation that many employees experience. Salaries, bonuses and other privileges exploit instincts for relative status, which attract particularly males to senior executive positions.

Evolutionary psychology and culture

Evolutionary psychology has traditionally focused on individual-level behaviors, determined by species-typical psychological adaptations. Considerable work, though, has been done on how these adaptations shape and, ultimately govern, culture (Tooby and Cosmides, 1989).
Tooby and Cosmides (1989) argued that the mind consists of many domain-specific psychological adaptations, some of which may constrain what cultural material is learned or taught.
As opposed to a domain-general cultural acquisition program, where an individual passively receives culturally-transmitted material from the group, Tooby and Cosmides (1989), among others, argue that: “the psyche evolved to generate adaptive rather than repetitive behavior, and hence critically analyzes the behavior of those surrounding it in highly structured and patterned ways, to be used as a rich (but by no means the only) source of information out of which to construct a ‘private culture’ or individually tailored adaptive system; in consequence, this system may or may not mirror the behavior of others in any given respect.” (Tooby and Cosmides 1989).

Epidemiological culture

The Epidemiology of representations, or cultural epidemiology, is a broad framework for understanding cultural phenomena by investigating the distribution of mental representations in and through populations.
The theory of cultural epidemiology was largely developed by Dan Sperber to study society and cultures. The theory has implications for psychology and anthropology. Mental representations are transferred from person to person through cognitive causal chains. Sperber (2001) identified three different, yet interrelated, cognitive causal chains.
A cognitive causal chain (CCC) links a perception to an evolved, domain-specific response or process. For example:

“On October 31, at 7:30 p.m., Mrs. Jones’s doorbell rings. Mrs. Jones hears the doorbell, and assumes that there is somebody at the door. She remembers it is Halloween: she enjoyed receiving treats as a child, and now, as an adult, she enjoys giving them. She guesses that there must be children at the door ready to trick-or-treat, and that, if she opens, she will be able to give them the candies she has bought for the occasion. Mrs. Jones decides to open the door, and does so.”

Social Cognitive Causal Chains (SCCC) are inter-individual CCCs. Here, a CCC is used as an act of communication between people (i.e. the mental representation is shared between multiple people). Elaborating on the previous example:

“On October 31, at 7:30 p.m., Mrs. Jones’s doorbell rings. Mrs. Jones hears the doorbell, and assumes that there is somebody at the door. She remembers it is Halloween: she enjoyed receiving treats as a child, and now, as an adult, she enjoys giving them. She guesses that there must be children at the door ready to trick-or-treat, and that, if she opens, she will be able to give them the candies she has bought for the occasion. Mrs. Jones decides to open the door, and does so.”

Cultural Cognitive Causal Chains (CCCCs) are those SCCCs which are shared and reproduced widely among a population.

The stability and longevity of these representations relies on their relevance and domain-specificity. This separates the epidemiology of representations from other evolutionary accounts of cultural transmission, namely memetics.

Evolutionary psychology and cultural evolution

Evolutionary psychological accounts of culture, especially cultural epidemiology, may seem at odds with other disciplines in psychology and anthropology, especially research in cultural evolution (e.g. Boyd and Richerson, 1985, 2005).

Cultural evolution, the domain of research focused on how culture changes through time due to different individual transmission mechanisms and population-level effects, often uses models derived from population genetics, in which agents are passive recipients of cultural traits (e.g. Bentley et al., 2004).

While evolutionary psychology has focused on how behavior may result from species-typical psychological programs which led to greater fitness in ancestral environments, this work has been criticized for neglecting how behavior may be shaped by culturally transmitted information. In contrast to genetic programs, cultural evolution investigates how culture itself may evolve (Mesoudi, 2009).
Gene-culture coevolution studies how culture and genetic evolution influence each other, ultimately shaping behavior, as well. Cultural evolution and evolutionary psychology may not be as disparate as one may think, though. Rather than a passive receptacle of cultural material, Boyd and Richerson (1985, 2005) suggest that our minds consist of psychological mechanisms which direct our attention to and imitate cultural traits depending on the frequency of that trait, the content of it, who carries it, etc. In this way, cultural evolution may be viewed as a particular kind of “scaling up” from the individual-level processes to population-level ones.

In neither account of culture is the mind a blank slate or empty bin for cultural material (Tooby and Cosmides, 1992). Some evolutionary psychologists have suggested that culturally-transmitted culture may pass through a number of lenses and filters shaped by natural selection to catch fitness-relevant information and behaviors; these filters may change due to local environmental conditions, sex, and other factors (Gangestad et al., 2006).
Boyer (2000) argued that evolutionary psychology, and anthropology in general, should investigate how these cognitive predispositions to cultural material affect their representation in following generations.
This research program may help to unify the two fields (Boyer, 2000). Others have suggested that evolutionary psychology, human behavioral ecology, and cultural evolution all fit nicely with each other, ultimately answering different questions on human behavioral diversity; gene-culture coevolution may be at odds with other research programs though by placing more emphasis on socially-learned behavior and its influence on human evolution (Brown et al., 2011)

Evolutionary psychology and human behavioral ecology

Human Behavioral Ecology (HBE) studies how ecology and social factors shape human behavioral variability. A key assumption of human behavioral ecology is that individuals will act in response to environmental factors in ways that enhance their fitness.
While both HBE and evolutionary psychology are both concerned with fitness benefits and natural selection, HBE is not typically concerned with mechanisms or how humans display adaptive behaviors in novel environments.

If the human mind took its present form and evolved in the African Pleistocene, why should one expect to behave adaptively in the present and in so many new environments?
Human Behavioral Ecologists may respond by stating that humans evolved as ecological generalists and display a wide range of variable behaviors to maximize fitness.
Where cooperation and food-sharing among extant hunter-gatherers may be seen as the result of kin-selection psychological mechanisms by an evolutionary psychologist, a human behavioral ecologist may attribute this behavior to optimal risk-reduction strategies and reciprocal altruism.

For Human Behavioral Ecology, cultural behaviors should tend towards optimality (i.e. higher fitness) in their current environment. For evolutionary psychology, cultural behaviors are the result of psychological mechanisms which were selected for in ancestral environments.

Evoked and transmitted culture

The difference between cultural behaviors acquired through selective transmission mechanisms and behaviors resulting from psychological adaptations has resulted in some researchers differentiating between evoked and transmitted culture (Tooby and Cosmides, 1992).

Evoked cultural behaviors are those that are the outputs of shared psychological mechanisms in response to local environmental cues Fessler et al., 2015).

Transmitted cultural behaviors are those behaviors which are learned from one’s social group, regardless of environment.

As such, investigating evoked culture may well rest in the domain of evolutionary psychology and transmitted culture studied by culture evolution, social psychology, and other disciplines.
Differentiating between the two is more difficult than it may appear, however. For example, given the level of cross-cultural variation in human societies, variation between any two cultures may result from separate histories and cultural evolutionary pathways or different evoked cultures, based on different local environmental cues, while uniformity across cultures could result from convergent cultural evolution or similarly functioning psychological adaptations (Fessler et al., 2015).
Specifically, if two cultures exhibit similar behaviors to avoid pathogens, can one differentiate between either the two groups independently inventing similar behaviors or the groups displaying the same underlying psychological adaptation for pathogen avoidance?

As well, the issue of behavioral variation and transmitted culture may be seen as a major point of contention between evolutionary psychology and other disciplines, especially gene-culture coevolution. Evolutionary psychology and human behavioral ecology both admit to cultural transmission as a source of behavioral variation but do not see it as an evolutionary process or its potential to have significantly affected human evolution.

Gene-culture coevolution would argue that culture traits may have altered genetic change and selection pressures, ultimately affecting cognition. However, as Brown et al. (2011) states:”Whether human behavioural ecologists and evolutionary psychologists are willing to accommodate the idea that some portion of human behavioural diversity could result from genetic differences that have arisen via selection pressures imposed by socially transmitted behaviour remains to be seen.”

While this may difficult, some evolutionary psychologists, such as Gangestad, Haselton, and Buss (2006) have argued that the future of the discipline rests on unifying transmitted and evoked culture. In order to do so, the authors suggest that a more comprehensive definition of culture needs to be developed since different cultural phenomena need different kinds of analysis to investigate their effects.
As they state, “Culture, however, is not a “thing” with singularity; it’s an umbrella concept subsuming a collection of extraordinarily varied phenomena, each of which requires scientific analysis” (Gangestad et al., 2006), the issues of behavioral variation through evoked or transmitted culture must rest on empirical evidence.

Psychology, culture, and human evolution

While most researchers would accept the notion that psychological adaptations, shaped by natural selection, underlie culture, some would stress the strength of cultural behaviors on shaping selection pressures (Boyd and Richerson, 2005) or emphasize cultural niche construction (Laland et al., 2000).
Still others have argued for a kind of cognitive niche construction, where culture changes the selection pressures on cognition, resulting in emergent psychological modules (e.g. Wheeler and Clark, 2008).
Wheeler and Clark (2008) have named this interplay between genes, culture, and embodiment the “triple helix.” The authors suggest that self-created environmental structures and reliance on culturally-transmitted information selected for cognitive modules for continual bootstrapping and increases in computational complexity. Their argument relies on cognitive niche construction, where culturally-learned behaviors create a space for new feedback cycles. By shaping the physical space around oneself, for example, the culturally-transmitted practice transform problem solving for new forms of thought.

The feedback cycle, as they and others argue, will alter selection pressures for cognitive developmental programs which bolster these abilities. As they state, “Triple helix models of mind recognize the role of genetic biases in sculpting key developmental trajectories, and the resulting space both for strong forms of genetically specified cognitive modularity and for weaker forms of emergent modularity resulting from trajectories marked by multiple bouts of culturally scaffolded experience and the self- selection of environments” (Wheeler and Clark, 2008.
Other authors have suggested that borrowing methods of dynamical systems analysis may help unravel this tangled web of genes, cognition, and culture (Kenrick et al., 2003). The answers to these type of questions have impacts on anthropology, social psychology, and other behavioral sciences (Mesoudi, 2009).

Wikipedia

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