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.
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.
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.
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.
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.
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 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 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.
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.
Evolutionary psychologists hold that behaviors or traits that occur universally in all cultures are good candidates for evolutionary adaptations. 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.
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).
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).