Evolutionary psychology

Kick the tires and light the fires, problem officially solevd! Evolutionary psychology (EP) examines psychological traits — such as memory, perception, or language — 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. 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, arguing that the mind has a modular structure similar to that of the body with different modules having adapted to serve 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. Psychological 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. Evolutionary psychology emphasizes the importance of kin selection and reciprocity in allowing for prosocial traits such as altruism to evolve. Like chimps 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.

Evolutionary psychologists hold that behaviors or traits that occur universally in all cultures are good candidates for evolutionary 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). Basic gender differences, such as greater eagerness for sex among men and greater coyness among women, are explained as 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.

Evolutionary psychology has its historical roots in Charles Darwin’s theory of natural selection. Darwin's theory inspired William James’s functionalist approach to psychology. Along with W.D. Hamilton's (1964) seminal papers on inclusive fitness, E. O. Wilson's Sociobiology (1975) helped to establish evolutionary thinking in psychology and the other social sciences. While some critics argue that evolutionary psychology hypotheses are difficult or impossible to test, evolutionary psychologists assert that is not impossible and, indeed, that many empirical studies have either generally corroborated or disconfirmed evidence regarding hypotheses about specific psychological adaptations. The influence of adaptationist approaches in psychology has been steadily increasing.

Overview

Evolutionary psychology (EP) is an approach 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:

"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." 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." 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.

EP proposes that the human brain comprises 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.

EP has roots in cognitive psychology and evolutionary biology. It also draws on behavioral ecology, artificial intelligence, genetics, ethology, anthropology, archaeology, biology, and zoology. EP 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 behaviour. Most of what is now labeled as sociobiological research is now conducted in the field of behavioral ecology.

EP has been applied to the study of many fields, including economics, aggression, law, psychiatry, politics, literature, and sex.

Nikolaas Tinbergen's four categories of questions can help to clarify the distinctions between several different, but complementary, types of explanations. Evolutionary psychology focuses on the the "why?" questions, while traditional psychology focuses on the "how?" questions.. Whilst this is the claim, the methodology of at least parts of the evolutionary psychology research programme does not always live up to this. For example, in the crucial area of applying Hamilton's Rule to explanations of social behaviour, prominent Evolutionary Psychologists (e.g. Daly and Wilson) typically do indeed make claims about the proximate mechanisms of altruistic and selfish behaviours. The ambition of Sociobiology and evolutionary psychology to elevate biology to a position of explaining ongoing patterns of human social behaviour and organization (which has traditionally been the anthropological study of kinship) was a central point upon which the sociobiology controversy ignited in the 1970s. Recent work has clarified the mistakes made over incorrect interpretation of Hamilton's Rule, and has shown that the proximate mechanisms are non-deterministic in respect of consanguineous relatedness. The thirty year stand-off over kinship is thus resolved, though largely in favour of the cultural anthropologists rather than evolutionary psychologists.

		Sequential vs. Static Perspective
		Historical/Developmental Explanation of current form in terms of a historical sequence	Current Form Explanation of the current form of species
How vs. Why Questions	Proximate How an individual organism's structures function	Ontogeny Developmental explanations for changes in individuals, from DNA to their current form	Mechanism Mechanistic explanations for how an organism's structures work
	Evolutionary Why a species evolved the structures (adaptations) it has	Phylogeny The history of the evolution of sequential changes in a species over many generations	Adaptation A species trait that evolved to solve a reproductive or survival problem in the ancestral environment

Related disciplines

The content of EP has derived from, on the one hand, the biological sciences (especially evolutionary theory as it relates to ancient human environments, the study of paleoanthropology and animal behavior) and, on the other, the human sciences especially psychology. Evolutionary biology as an academic discipline emerged with the modern evolutionary synthesis in the 1930s and 1940s, although it was not until the 1970s and 1980s that university departments included the term evolutionary biology in their titles. Several behavioural subjects relate to this core discipline: in the 1930s the study of animal behaviour (ethology) emerged with the work of Dutch biologist Nikolaas Tinbergen and Austrian biologists Konrad Lorenz and Karl von Frisch.

In the 1970s, two major branches developed from ethology. Firstly, the study of animal social behavior (including humans) generated sociobiology, defined by its pre-eminent proponent Edward O. Wilson in 1975 as "the systematic study of the biological basis of all social behavior" and in 1978 as "the extension of population biology and evolutionary theory to social organization". Secondly, there was behavioral ecology which placed less emphasis on social behavior by focusing on the ecological and evolutionary basis of both animal and human behavior.

From psychology there are the primary streams of developmental, social and cognitive psychology. Establishing some measure of the relative influence of genetics and environment on behavior has been at the core of behavioral genetics and its variants, notably studies at the molecular level that examine the relationship between genes, neurotransmitters and behavior. Dual inheritance theory (DIT), developed in the late 1970s and early 1980s, has a slightly different perspective by trying to explain how human behavior is a product of two different and interacting evolutionary processes: genetic evolution and cultural evolution. DIT is a "middle-ground" between much of social science, which views culture as the primary cause of human behavioral variation, and human sociobiology and evolutionary psychology which view culture as an insignificant by-product of genetic selection.

Principles

Evolutionary psychology is founded on several core premises.

1. The brain in an information processing device, and it produces behavior in response to external and internal inputs.
2. The brain's adaptive mechanisms were shaped by natural and sexual selection.
3. Different neural mechanisms are specialized for solving adaptive problems in humanity's evolutionary past.
4. 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.
5. 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.
6. Human psychology consists of many specialized mechanisms, each sensitive to different classes of information or inputs. These mechanisms combine to produce manifest behavior.

Evolutionary psychologists suggest that EP 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 it has for biology.

History

19th century

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, The Origin of Species, 1859, p. 449.

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.

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.

Post world war II

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 divisions between biologists.

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 sociobiology. According to Wilson, the heated controversies surrounding Sociobiology:The New Synthesis, significantly stigmatized the term "sociobiology".

Origin of evolutionary psychology

The term evolutionary psychology was probably coined 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 highly influential 1992 book The Adapted Mind: Evolutionary Psychology and The Generation of Culture.

Evolutionary psychologists emphasized that organisms are "adaptation executors" rather than "fitness maximizers." In other words, organisms use behaviors that they were adpative in the past rather than those that maximize fitness in the present. This distinction helps explain maladaptive behaviors, which are "fitness lags" resulting from novel environments. In addition, 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.

General evolutionary theory

Main article: Evolution

EP is sometimes seen not simply as a subdiscipline of psychology but as a way in which evolutionary theory can be used as a metatheoretical framework within which to examine the entire field of psychology.

File:Darwin's finches.jpeg

Darwin's illustrations of beak variation in the finches of the Galápagos Islands.

Natural selection

Natural selection, a key component of evolutionary theory, involves three main ingredients:

• Genetically based inheritance of traits - some traits are passed down from parents to offspring in genes,
• Variation - heritable traits vary within a population (now we know that mutation is the source of some of this genetic variation),
• Differential survival and reproduction - these traits will vary in how strongly they promote the survival and reproduction of their bearers.

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 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:

• Intersexual selection, which refers to the traits that one sex generally prefers in the other sex, (e.g. the peacock's tail).
• Intrasexual competition, which refers to the competition among members of the same sex for mating access to the opposite sex, (e.g. two stags locking antlers).

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.

Overview of Theoretical Foundations

Central Concepts

System level	Problem	Author	Basic ideas	Example adaptations
Individual	How to survive?	Charles Darwin (1859)	Natural Selection (or "survival selection") The bodies and minds of organisms are made up of evolved adaptations designed to help the organism survive in a particular ecology (for example, the fur of polar bears, the eye, food preferences, etc.).	Bones, skin, vision, pain perception, etc.
Dyad	How to attract a mate and/or compete with members of one's own sex for access to the opposite sex?	Charles Darwin (1871)	Sexual selection Organisms can evolve physical and mental traits designed specifically to attract mates (e.g., the Peacock's tail) or to compete with members of one's own sex for access to the opposite sex (e.g., antlers).	Peacock's tail, antlers, courtship behavior, etc.
Family & Kin	Gene replication. How to help those with whom we share genes survive and reproduce?	W.D. Hamilton (1964)	Inclusive fitness (or "gene's eye view", "kin selection") / Evolution of sexual reproduction Selection occurs most robustly at the level of the gene, not the individual, group, or species. Reproductive success can thus be indirect, via shared genes in kin. Being altruistic toward kin can thus have genetic payoffs. (Also see Gene-centered view of evolution) Also, Hamilton argued that sexual reproduction evolved primarily as a defense against pathogens (bacteria and viruses) to "shuffle genes" to create greater diversity, especially immunological variability, in offspring.	Altruism toward kin, parental investment, the behavior of the social insects with sterile workers (e.g., ants).
Kin and Family	How are resources best allocated in mating and/or parenting contexts to maximize inclusive fitness?	Robert Trivers (1972)	Parental Investment Theory / Parent - Offspring Conflict / Reproductive Value The two sexes often have conflicting strategies regarding how much to invest in offspring, and how many offspring to have. Parents allocate more resources to their offspring with higher reproductive value (e.g., "mom always liked you best"). Parents and offspring may have conflicting interests (e.g., when to wean, allocation of resources among offspring, etc.)	Sexually dimorphic adaptations that result in a "battle of the sexes," parental favoritism, timing of reproduction, parent-offspring conflict, sibling rivalry, etc.
Non-kin small group	How to succeed in competitive interactions with non-kin? How to select the best strategy given the strategies being used by competitors?	Neumann & Morgenstern (1944); John Smith (1982)	Game Theory / Evolutionary Game Theory Organisms adapt, or respond, to competitors depending on the strategies used by competitors. Strategies are evaluated by the probable payoffs of alternatives. In a population, this typically results in an "evolutionary stable strategy," or "evolutionary stable equilibrium" -- strategies that, on average, cannot be bettered by alternative strategies.	Facultative, or frequency-dependent, adaptations. Examples: hawks vs. doves, cooperate vs. defect, fast vs. coy courtship, etc.
Non-kin small group	How to maintain mutually beneficial relationships with non-kin in repeated interactions?	Robert Trivers (1971)	"Tit for Tat" Reciprocity A specific game strategy (see above) that has been shown to be optimal in achieving an evolutionary stable equilibrium in situations of repeated social interactions. One plays nice with non-kin if a mutually beneficially reciprocal relationship is maintained across multiple interactions, while cheating is punished.	Cheater detection, emotions of revenge and guilt, etc.
Non-kin, large groups governed by rules and laws	How to maintain mutually beneficial relationships with strangers with whom one may interact only once?	Herbert Gintis (2000, 2003) and others	Generalized Reciprocity (Also called "strong reciprocity"). One can play nice with non-kin strangers even in single interactions if social rules against cheating are maintained by neutral third parties (e.g., other individuals, governments, institutions, etc.), a majority group members cooperate by generally adhering to social rules, and social interactions create a positive sum game (i.e., a bigger overall "pie" results from group cooperation). Generalized reciprocity may be a set of adaptations that were designed for small in-group cohesion during times of high inter-tribal warfare with out-groups. Today the capacity to be altruistic to in-group strangers may result from a serendipitous generalization (or "mismatch") between ancestral tribal living in small groups and today's large societies that entail many single interactions with anonymous strangers. (The dark side of generalized reciprocity may be that these adaptations may also underlie aggression toward out-groups.)	To in-group members: Capacity for generalized altruism, acting like a "good Samaritan," cognitive concepts of justice, ethics and human rights. To out-group members: Capacity for xenophobia, racism, warfare, genocide.
Large groups / culture.	How to transfer information across distance and time?	Richard Dawkins (1976), Susan Blackmore (2000), Boyd & Richerson (2004)	Memetic Selection / Memetics / Dual inheritance theory Genes are not the only replicators subject to evolutionary change. Cultural characteristics, also referred to as "Memes" (e.g., ideas, rituals, tunes, cultural fads, etc.) can replicate and spread from brain to brain, and many of the same evolutionary principles that apply to genes apply to memes as well. Genes and memes may at times co-evolve ("gene-culture co-evolution").	Language, music, evoked culture, etc. Some possible by-products, or "exaptations," of language may include writing, reading, mathematics, etc.

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

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.

Products of Evolution: Adaptations, Exaptations, Byproducts, and Random Variation

Not all traits of organisms are adaptations. As noted in the table below, traits may also be exaptations, byproducts of adaptations (sometimes called "spandrels"), or random variation between individuals. For more on these distinctions, see Buss, et al., (1998).

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 an 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.

	Adaptation	Exaptation	By-Product	Random Noise
Definition	Organismic trait designed to solve an ancestral problem(s). Shows complexity, special “design”, functionality	Adaptation that has been “re-designed” to solve a different adaptive problem.	Byproduct of an adapative mechanism with no current or ancestral function	Random variations in an adaptation or byproduct
Physiological Example	Bones / Umbilical cord	Small bones of the inner ear	White color of bones / Belly button	Bumps on the skull, convex or concave belly button shape
Psychological Example	Toddlers’ ability to learn to talk with minimal instruction.	?	Ability to learn to read and write.	Within-sex variations in voice pitch.

Cultural Universals

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.

Environment of evolutionary adaptedness

EP 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.

Definition

The 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.

Human EEA

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. In broad terms, these problems include those of growth, development, differentiation, maintenance, mating, parenting, and social relationships.

The EEA is significantly different from modern society. Our ancestors 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 our hunter-gatherer ancestors lived. Since hunter-gatherer societies are egalitarian, the ancestral population may have been egalitarian as well, a social pattern different from the hierarchies found in chimp bands. 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 Jetha argue that evolutionary psychologists have overemphasized our similarity to chimps, which are more violent, while underestimating our similarity to 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. In the environment in which ducks evolved, for example, attachment of ducklings to their mother had great survival value. 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 properly attach the duckling to the mother. In novel environments, however, the mechanism can malfunction by forming an attachment to a dog or human instead.

Because humans are mostly adapted to Pleistocene environments, psychological mechanisms sometimes 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, 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 our 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 it evolved. The term was coined by Nobel Laureate Niko Tinbergen to describe animal behavior, but Harvard psychologist Deirdre Barrett has pointed out that supernormal stimulation governs the behavior of humans as powerfully as that of animals. She explains junk food as an exaggerated stimulus to cravings for salt, sugar, and fats, and she describes how 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.

Research methods

Evolutionary 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. Recently, methods and tools have been introduced based on fictional scenarios, mathematical models, and multi-agent computer simulations.

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.

Actually antibiotics are known to bemcoe less effective the more often you take them. Take insulin for example, its not really an antibiotic but is holds a good story.Insulin WAS used as a wonder cure for potentialy hundreds of minor illnesses caused by germs. It was used extensively from the early 1900 s to about the 50 s or 60 s. If you were sick, you would get an insulin shot. Because of the exposure of these common germs to high levels of insulin, they have evolved to no longer be very effected by it. Because the main factor in evolution is a change in the organizims souroundings, the bacteria and germs got used to their enviroment that was full of insulin.Insulin is no longer a miracle cure, to the contrary, it is intentionaly not used a lot of the time where it would still be effective, just so they can protect its potentcy for future generations. If they used it for everything as they did before, it would slowly bemcoe ineffective to everything.Also think of the Bird Flew. Currently scientists are rather scared that it may cange into an airborn disease. Currently it is strictly by direct exposure, such as handling or eating an affected animal. The only way it could bemcoe a worldwide pandemic is if it evolved into an airborn disease.

Contributions of evolutionary psychology to traditional sub-fields of psychology

Proponents of EP suggests that adaptationism can serve as a foundational meta theory for the entire discipline and thus it may offer a way to integrate different psychological phenomenon. They suggest that evolutionary theory can integrate the entire field of psychological science in much they same way that evolutionary theory has integrated the field of biology.

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.

Controversies

The practice of applying evolutionary theory to animal behavior and to the human body is generally seen as 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. Trying to apply evolutionary theory to human behavior requires caution, and evolutionary psychology can easily go too far in doing so. In the past, evolutionary psychology failed to address the complexity of individual development and experience, making it vulnerable to criticism as genetic reductionism. From the genes to the social environment, interaction is the rule. Evidence that genes influence behavior does not explain how it does so in any individual case. A frequent critique of the discipline is that the hypotheses of evolutionary psychology are difficult or impossible to adequately test, thus questioning its status as an actual scientific discipline, for example because many current traits probably evolved to serve different functions than they do now. While testing the hypotheses of evolutionary psychology is difficult, in the majority viewpoint it is not impossible. Evolutionary Psychologists say that good evolutionary hypotheses can be corroborated or contradicted by data.

Evolutionary psychologists, in turn, accuse proponents of the standard social sciences model of political bias and argue that mind is better understood, not as a blank slate capable of learning anything with equal ease, but as a set of evolved emotional, motivational, and cognitive adaptations designed to help to solve recurrent problems of survival and reproduction in ancestral environments. However, there are many critics outside of the standard social sciences model, who debate the veracity of the computational theory of mind underlying evolutionary psychology. They argue that the computational theory of mind does not fit with our biological reality any more than does a mind shaped entirely by the environment.

References

• Barkow, Jerome H. (2006). Missing the Revolution: Darwinism for Social Scientists. Oxford University Press, USA. ISBN 0-19-513002-2. 
• Buss, David M. (2004). Evolutionary psychology: the new science of the mind. Boston: Pearson/A and B. ISBN 0-205-37071-3. 
• Clarke, Murray (2004). Reconstructing reason and representation. Cambridge, Mass: MIT Press. ISBN 0-262-03322-4. 
• Evan, Dylan (2000). Introducing Evolutionary Psychology. Lanham, MD: Totem Books USA. ISBN 1-84046-043-1. 
• Joyce, Richard (2006). The Evolution of Morality (Life and Mind: Philosophical Issues in Biology and Psychology). Cambridge, Mass: The MIT Press. ISBN 0-262-10112-2. 
• Miller, Geoffrey P. (2000). The mating mind: how sexual choice shaped the evolution of human nature. Garden City, N.Y: Doubleday. ISBN 0-385-49516-1. 
• Pinker, Steven (1997). How the mind works. New York: Norton. ISBN 0-393-04535-8. 
• Pinker, Steven (2002). The blank slate: the modern denial of human nature. New York, N.Y: Viking. ISBN 0-670-03151-8. 
• Richards, Janet C. (2000). Human nature after Darwin: a philosophical introduction. New York: Routledge. ISBN 0-415-21243-X. 
• Ryan, C. & Jethá, C. (2010). Sex at Dawn: The Prehistoric Origins of Modern Sexuality. New York, NY: Harper. ISBN 0061707805. 
• Wilson, Edward Raymond (2000). Sociobiology: the new synthesis. Cambridge: Belknap Press of Harvard University Press. ISBN 0-674-00089-7. 
• Wright, Robert C. M. (1995). The moral animal: evolutionary psychology and everyday life. New York: Vintage Books. ISBN 0-679-76399-6. 
• Santrock, John W. (2005). The Topical Approach to Life-Span Development(3rd ed.). New York, N.Y: McGraw Hill. ISBN 0-07-322626-2. 

Further reading

• Confer, J.C., Easton, J.A., Fleischman, D.S., Goetz, C. D., Lewis, D.M.G., Perilloux, C., & Buss, D. M. (2010). Evolutionary Psychology: Controversies, Questions, Prospects, and Limitations. American Psychologist, 65, 110-126.
• Buss, D. M. (1995). Evolutionary psychology: A new paradigm for psychological science. Psychological Inquiry, 6, 1-30. Full text
• Durrant, R., & Ellis, B.J. (2003). Evolutionary Psychology. In M. Gallagher & R.J. Nelson (Eds.), Comprehensive Handbook of Psychology, Volume Three: Biological Psychology (pp. 1–33). New York: Wiley & Sons. Full text
• Kennair, L. E. O. (2002). "Evolutionary psychology: An emerging integrative perspective within the science and practice of psychology". Human Nature Review (2): 17–61. http://www.human-nature.com/nibbs/02/ep.html. 
• Medicus, G. (2005). "Evolutionary Theory of Human Sciences". pp. 9, 10, 11. http://homepage.uibk.ac.at/~c720126/humanethologie/ws/medicus/block1/inhalt.html. Retrieved 2009-09-08. 
• Tooby, J. & Cosmides, L. (2005). Conceptual foundations of evolutionary psychology. In D. M. Buss (Ed.), The Handbook of Evolutionary Psychology (pp. 5–67). Hoboken, NJ: Wiley. Full text

Academic societies

• Human Behavior and Evolution Society; international society dedicated to using evolutionary theory to study human nature
• The International Society for Human Ethology; promotes ethological perspectives on the study of humans worldwide
• European Human Behaviour and Evolution Association an interdisciplinary society that supports the activities of European researchers with an interest in evolutionary accounts of human cognition, behaviour and society
• The Association for Politics and the Life Sciences; international and interdisciplinary association concerned with evolutionary, genetic and ecological knowledge
• Society for Evolutionary Analysis in Law a scholarly association dedicated to fostering interdisciplinary exploration of issues at the intersection of law, biology, and evolutionary theory
• The New England Institute for Cognitive Science and Evolutionary Psychology aims to foster research and education into the interdisciplinary nexus of cognitive science and evolutionary studies
• The NorthEastern Evolutionary Psychology Society; regional society dedicated to encouraging scholarship and dialogue on the topic of evolutionary psychology
• Feminist Evolutionary Psychology Society researchers that investigate the active role that females have had in human evolution

Journals

• Evolutionary Psychology free access online scientific journal
• Evolution and Human Behavior; journal of the Human Behavior and Evolution Society
• Politics and the Life Sciences is an interdisciplinary peer-reviewed journal published by the Association for Politics and the Life Sciences
• Human Nature: An Interdisciplinary Biosocial Perspective advances the interdisciplinary investigation of the biological, social, and environmental factors that underlie human behavior. It focuses primarily on the functional unity in which these factors are continuously and mutually interactive. These include the evolutionary, biological, and sociological processes as they interact with human social behavior.
• Biological Theory: Integrating Development, Evolution and Cognition devoted to theoretical advances in the fields of biology and cognition, with an emphasis on the conceptual integration afforded by evolutionary and developmental approaches.
• Evolutionary Anthropology
• Behavioral and Brain Sciences interdisciplinary articles in psychology, neuroscience, behavioral biology, cognitive science, artificial intelligence, linguistics and philosophy. About 30% of the articles have focused on evolutionary analyses of behavior.
• Evolution and Development Research relevant to interface of evolutionary and developmental biology
• Journal of Social, Evolutionary & Cultural Psychology
• Biological Theory: Integrating Development, Evolution and Cognition; publishes theoretical advances in the fields of biology and cognition, emphasizing the conceptual integration afforded by evolutionary and developmental approaches. Free access to Winter 2006 issues
• The Evolutionary Review - Art, Science, and Culture

Videos

• Brief video clip re what EP is (from the "Evolution" PBS Series)
• TED talk by Steven Pinker about his book The Blank Slate: The Modern Denial of Human Nature
• Video interview with Steven Pinker by Robert Wright (journalist) discussing evolutionary psychology
• Video interview with Edward O. Wilson by Robert Wright (journalist), contextualizing evolutionary psychology within science, politics, academics and philosophy