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Evolutionary psychology (EP) attempts to explain psychological traits—such as memory, perception, or language—as adaptations, that is, as the functional products of natural selection or sexual selection. Adaptationist thinking about physiological mechanisms, such as the heart, lungs, and immune system, is common in evolutionary biology. Evolutionary psychology applies the same thinking to psychology. Modern evolutionary psychologists (see, for example, Confer, Easton, Fleischman, Goetz, Lewis, Perilloux & Buss, 2010; as well as Buss, 2005; Durrant & Ellis, 2003; Pinker, 2002; Tooby & Cosmides, 2005) argue that much of human behavior is generated by psychological adaptations that evolved to solve recurrent problems in human ancestral environments. They hypothesize, for example, that humans have inherited special mental capacities for acquiring language, making it nearly automatic, while inheriting no capacity specifically for reading and writing. Other adaptations, according to EP, might include the abilities to infer others' emotions, to discern kin from non-kin, to identify and prefer healthier mates, to cooperate with others, and so on. Consistent with the theory of natural selection, evolutionary psychology sees organisms as often in conflict with others of their species, including mates and relatives. For example, mother mammals and their young offspring sometimes struggle over weaning, which benefits the mother more than the child. Humans, however, have a marked capacity for cooperation under certain conditions as well. Evolutionary psychologists see those behaviors and emotions that are nearly universal, such as fear of spiders and snakes, as more likely to reflect evolved adaptations. 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). This view is contrary to the idea that human mental faculties are general-purpose learning mechanisms. Fields closely related to EP are animal behavioral ecology, human behavioral ecology, dual inheritance theory, and sociobiology.
OverviewEvolutionary psychology (EP) is an approach to the entire discipline that views human nature as a universal set of evolved psychological adaptations to recurring problems in the ancestral environment. Proponents of EP suggest that it seeks to heal a fundamental division at the very heart of science --- that between the soft human social sciences and the hard natural sciences, and that the fact that human beings are living organisms demands that psychology be understood as a branch of biology. Anthropologist John Tooby and psychologist Leda Cosmides note:
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. Light will be thrown on the origin of man and his history. Charles Darwin, On the Origin of Species
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." EP is, to quote Steven Pinker, "not a single theory but a large set of hypotheses" and a term which "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." EP proposes that the human brain comprises many functional mechanisms,2 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. EP has roots in cognitive psychology and evolutionary biology (See also sociobiology). It also draws on behavioral ecology, artificial intelligence, genetics, ethology, anthropology, archaeology, biology, and zoology. EP is closely linked to sociobiology,citation needed 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 behaviour. Most sociobiological research is now conducted in the field of behavioral ecology.citation needed The term evolutionary psychology was probably coined by American biologist Michael Ghiselin in a 1973 article published in the journal Science.3 Jerome Barkow, Leda Cosmides and John Tooby popularized the term "evolutionary psychology" in their highly influential 1992 book The Adapted Mind: Evolutionary Psychology and The Generation of Culture.4 EP has been applied to the study of many fields, including economics, aggression, law, psychiatry, politics, literature, and sex. EP uses Nikolaas Tinbergen's four categories of questions and explanations of animal behavior. Two categories are at the species level; two, at the individual level, as noted in the table below.
The species-level categories (often called "ultimate explanations") are
The individual-level categories are
Evolutionary psychology mostly focuses on the adaptation (functional) category. PrinciplesEvolutionary psychology is a hybrid discipline that draws insights from modern evolutionary theory, biology, cognitive psychology, anthropology, economics, computer science, and paleoarchaeology. The discipline rests on a foundation of core premises. According to evolutionary psychologist David Buss, these include:
Similarly, pioneers of the field Leda Cosmides and John Tooby consider five principles to be the foundation of evolutionary psychology:
Evolutionary psychology is founded on the computational theory of mind, the theory that the mind, our "inner world," is the action of complex neural structures in the brain. For example, when a child shrinks in fear from a spider, the child's brain has attended to the spider, computed that it's a potential threat, and initiated a fear response. General evolutionary theory
Evolutionary psychology is rooted in evolutionary theory, especially animal ethology as represented by the work of Niko Tinbergen and Konrad Lorenz. It is sometimes seen not simply as a sub-discipline of psychology but as a way in which evolutionary theory can be used as a meta-theoretical framework within which to examine the entire field of psychology.5 A few biologists challenge the basic premises of evolutionary psychology.6 Natural selectionMain article: Natural selection
Natural selection, a key component of evolutionary theory, involves three main ingredients:
Selection refers to the process by which environmental conditions "select" organisms with the appropriate traits to survive; these organisms will have such traits more strongly represented in the next generation. This is the basis of adaptive evolution. The insight of Wallace and Darwin was that this "natural selection" was creative - it could lead to new traits and even new species, it was based on differential survival of variable individuals, and it could explain the broad scale patterns of evolution. Sexual selectionMain article: Sexual selection
Many traits that are selected for can actually hinder survival of the organism while increasing its reproductive opportunities. Consider the classic example of the peacock's tail. It is metabolically costly, cumbersome, and essentially a "predator magnet." What the peacock's tail does do is attract mates. Thus, the type of selective process that is involved here is what Darwin called "sexual selection." Sexual selection can be divided into two types:
Inclusive fitnessInclusive fitness theory, which was proposed by William D. Hamilton in 1964 as a revision to evolutionary theory, is essentially a combination of natural selection, sexual selection, and kin selection. It refers to the sum of an individual's own reproductive success in addition to the effects the individual's actions have on the reproductive success of their genetic relatives. 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: 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. However, in recent years group selection has been making a comeback (albeit a controversial one) as multilevel selection, which posits that evolution can act not just on the "gene" level but on many levels of functional organization, including the "group" level. Foundations
Source:7 Middle-level evolutionary theories
Middle-level evolutionary theories are theories that encompass broad domains of functioning.citation needed They are compatible with general evolutionary theory but not derived from it.citation needed Furthermore, they are applicable across species. During the early 1970s, three very important middle-level evolutionary theories were contributed by Robert Trivers8910
Additional middle-level evolutionary theories used in EP include:
Evolved psychological mechanismsMain article: Evolved psychological mechanisms
At a proximal level, 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. While philosophers have generally considered human mind to include broad faculties, such as reason and lust, evolutionary psychologists describe EPMs as narrowly evolved to deal with specific issues, such as catching cheaters or choosing mates. Some mechanisms, termed domain-specific, deal with recurrent adaptive problems over the course of human evolutionary history. Domain-general mechanisms, on the other hand, deal with evolutionary novelty. Environment of evolutionary adaptednessEP 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, or EEA for short.11 DefinitionThe term environment of evolutionary adaptedness was coined by John Bowlby as part of attachment theory. It refers to the environment to which a particular evolved mechanism is adapted. More specifically, the EEA 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. In the environment in which ducks evolved, for example, attachment of ducklings to their mother had great survival value for the ducklings. Because the first moving being that a duckling was likely to see was its mother, a psychological mechanism that evolved to form an attachment to the first moving being would therefore properly function to form an attachment to the mother. In novel environments, however, the mechanism can malfunction by forming an attachment to a dog or human instead. Human EEAMain article: Human evolution
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 1.8 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.12 In broad terms, these problems include those of growth, development, differentiation, maintenance, mating, parenting, and social relationships. MismatchesIf humans are mostly adapted to Pleistocene environments, then some psychological mechanisms should occasionally exhibit "mismatches" to the modern environment, similar to the attachment patterns of ducks. One example is the fact that although about 10,000 people are killed with guns in the US annually,13 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.14 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 our evolved fear-learning psychology and the modern environment.1516 Research methodsEvolutionary psychologists use several methods and data sources to test their hypotheses, as well as various comparative methods to test for similarities and differences between: humans and other species, males and females, individuals within a species, and between the same individuals in different contexts. They also use more traditional experimental methods involving, for example, dependent and independent variables. Evolutionary psychologists also use various sources of data for testing, including archeological records, data from hunter-gatherer societies, observational studies, self-reports, public records, and human products.17 Areas of researchAreas of research in evolutionary psychology can be divided into broad categories of adaptive problems that arise from the broader theory of evolution itself: survival, mating, parenting, kinship, and group living. SurvivalThe Hunting Hypothesis might explain the emergence of human coalitions as a psychological mechanism. With men being the providers for the family, their lives depended on hunting wild game. They could not risk going about such an arduous task on their own. If they did it alone they risked not catching anything at all. Also, the meat would spoil if they caught a large animal and could not finish it on their own. Therefore, they hunted together with other men and shared their food. These human coalitions can be seen today. One form of evolutionary adaptiveness can be found in morning sickness in women during their first trimester. Over thousands of years, women's bodies have adapted to the dangers that the environment may pose to the developing fetus when they eat something. Therefore, during this time many women experience disgust and even vomiting when eating certain foods which may be toxic to the fetus. Vomiting is the body's way of coping with the toxins in the environment and keeping them from reaching the child during this critical period when the vital organs are being formed. The function of this physiological reaction was to protect the fetus. MatingGiven that sexual reproduction is the means by which genes are propagated into future generations, sexual selection plays a large role in the direction of human evolution. Human mating, then, is of interest to evolutionary psychologists who aim to investigate evolved mechanisms to attract and secure mates.18 Several lines of research have stemmed from this interest, such as studies of mate selection1920,21 mate poaching,22 and mate retention,23 to name a few. Much of the research on human mating is based on parental investment theory,24 which makes important predictions about the different strategies men and women will use in the mating domain (see above under "Middle-level evolutionary theories"). In essence, it predicts that women will be more selective when choosing mates, whereas men will not, especially under short-term mating conditions. This has led some researchers to predict sex differences in such domains as sexual jealousy 2526 (however, see also,)27, wherein females will react more aversively to emotional infidelity and males will react more aversively to sexual infidelity. This particular pattern is predicted because the costs involved in mating for each sex are distinct. Women, on average, should prefer a mate who can offer some kind of resources (e.g., financial, commitment), which means that a woman would also be more at risk for losing those valued traits in a mate who commits an emotional infidelity. Men, on the other hand, are limited by the fact that they can never be certain of the paternity of their children because they do not bear the offspring themselves. This obstacle entails that sexual infidelity would be more aversive than emotional infidelity for a man because investing resources in another man's offspring does not lead to propagation of the man's own genes. Another interesting line of research is that which examines women's mate preferences across the ovulatory cycle28.29 The theoretical underpinning of this research is that ancestral women would have evolved mechanisms to select mates with certain traits depending on their hormonal status. For example, the theory hypothesizes that, during the ovulatory phase of a woman's cycle (approximately days 10-15 of a woman's cycle)30, a woman who mated with a male with high genetic quality would have been more likely, on average, to produce and rear a healthy offspring than a woman who mated with a male with low genetic quality. These putative preferences are predicted to be especially apparent for short-term mating domains because a potential male mate would only be offering genes to a potential offspring. This hypothesis allows researchers to examine whether women select mates who have characteristics that indicate high genetic quality during the high fertility phase of their ovulatory cycles. Indeed, studies have shown that women's preferences vary across the ovulatory cycle. In particular, Haselton and Miller (2006) showed that highly fertile women prefer creative but poor men as short-term mates. Creativity may be a proxy for good genes.31 Research by Gangestad et al. (2004) indicates that highly fertile women prefer men who display social presence and intrasexual competition; these traits may act as cues that would help women predict which men may have, or would be able to acquire, resources. Evolutionary Developmental PsychologyMain article: Evolutionary developmental psychology
In evolutionary theory, what matters most is that individuals live long enough to reproduce and pass on their genes. So why do humans live so long after reproduction? Many evolutionary psychologists have proposed that living a long life improves the survival of babies because while the parents were out hunting, the grandparents cared for the young. According to Paul Baltes, the benefits granted by evolutionary selection decrease with age. Natural Selection has not eliminated many harmful conditions and nonadaptive characteristics that appear among older adults, such as Alzheimer disease. If it were a disease that killed 20 year-olds instead of 70 year-olds this may have been a disease that natural selection could have destroyed ages ago. Thus, unaided by evolutionary pressures against nonadaptive conditions, we suffer the aches, pains, and infirmities of aging. And as the benefits of evolutionary selection decrease with age, the need for culture increases.32 History19th centuryAfter 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.33 Darwin anticipated evolutionary psychology with this quote from the Origin of Species:
According to Noam Chomsky, the founder of evolutionary psychology might have been Peter Kropotkin, who argued in his 1902 book Mutual Aid: A Factor of Evolution for the evolutionary benefits of behavioral traits related to mutual aid. 34 Post world war IIWhile 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. SociobiologyIn 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. The specific chapter caused considerable controversy as it reignited the nature versus nurture debate. E O Wilson argues that the field of evolutionary psychology is essentially the same as sociobiology.35 According to Wilson, the heated controversies surrounding Sociobiology:The New Synthesis, significantly stigmatized the term "sociobiology". Evolutionary psychology emerged as a more acceptable term in the 1980s that was not tainted by earlier controversies, and also emphasized that organisms are "adaptation executors" rather than "fitness maximizers" (which can help to explain maladaptive behaviors due to "fitness lags" given novel environmental changes).3637 ControversiesMain article: Evolutionary psychology controversy
Applying evolutionary theory to animal behavior is uncontroversial. However, adaptationist approaches to human psychology are contentious, with critics questioning the scientific nature of evolutionary psychology, and with more minor debates within the field itself.3839 Criticisms of the field have also been addressed by scholars.40 See also
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