There is evidence that language has some innate basis. Babies are born with certain expectations as to how language works, and language learning, according to Chomsky, is simply a matter of parameter setting. Pinker and Bloom (1990) take an evolutionary perspective on language. Chomsky’s recent theoretical work suggests that very little of the language ‘organ’ is specific to language. Some language deficits have been traced to a malfunctioning variant of the gene FOXP2. While this initially excited attention as ‘the language gene’ or ‘the grammar gene’, subsequent research has shown the true story to be more complicated. Research suggests that language may well have been around for almost 2 million years. There are a number of hypotheses suggesting that language evolved to fulfil a social function, such as social grooming (binding groups together), the making of social contracts (to enable monogamy) and the use of language to impress potential mates.

Evolutionary psychologists use the concept of reciprocal altruism/direct reciprocation to help explain cooperative behaviour. Direct reciprocation consists of self-sacrificing acts between two unrelated individuals that are based on delayed reciprocation. Documented cases of reciprocity are known in non-human species including the giving of regurgitated blood between vampire bats and mutual aid in vervet monkeys. Tit-for-tat has been labelled an evolutionarily stable strategy, or ESS. An ESS is a strategy that cannot be bettered provided sufficient members of a group adopt it. Humans playing prisoner’s dilemma repeatedly develop the ESS tit-for-tat strategy. This suggests that humans seek a willingness to cooperate but also bear a grudge when this cooperation is not reciprocated. Aggression and violence between the sexes covers: sexual harassment, intimate partner violence and rape. While rape and sexual harassment are almost exclusively male preserves, intimate partner violence involving female-on-male acts is actually slightly more common than the reverse.

Rather than thinking of nature versus nurture it is better to think about interactions between genes and the environment. The Santa Barbara School of evolutionary psychology proposed that human cognition is the result of innately specified domain-specific mental modules. Babies have certain expectations of the way that the physical world operates. Infants of at least three months of age have the knowledge that objects exist independently of their ability to perceive them. Babies have preference for face-like stimuli from birth and learn the details of human faces rapidly. Young children have an understanding of the role of mental states as a cause of behaviour. This skill, known as theory of mind, becomes more sophisticated as children develop. It is measured by a number of tasks such as false belief task and the eyes test, in which participants are required to judge how people feel from looking at their eyes.

Early theories of culture tended to reject the importance of biology in explaining cultural phenomena. Instead culture was seen as a superorganism unaffected by human nature. In contrast to the view of the cultural relativists, Donald Brown argued that there are many cultural universals, and some of these might be the product of a comparatively fixed underlying human nature. Tooby and Cosmides propose that evoked culture might give rise to contingent universals, practices that are the result of mental models being sensitive to certain environmental conditions. Many evolutionists argue that many cultural practices are constrained by genes; culture exists to improve our inclusive fitness. Richerson and Boyd are more concerned with how our ability to acquire and learn culture evolved, what factors led to the ‘cultural revolution’. They argue that culture provides us with a second mode of inheritance that evolved as a way of adapting to an environment.

The cognitive approach sees behaviour as resulting from the operation of internal mental processes. Our visual systems did not evolve to present us with a true description of the world; rather, they evolved to give us a useful description of the world that supports our actions upon it. We can see this in perceptual constancies in which a changing world is stabilized by the actions of our visual system, resulting in visual illusions. Although problems such as under-age drinking are often thought of as problems of logic (such as the abstract Wason task), they are perhaps better thought of as problems of duties and obligation and play a role in detecting freeriders to better enable cooperation. Statistical misconceptions such as the gambler’s fallacy and the hot hand fallacy may arise from our sensitivity to the patchiness of the world that we inhabit.

Evolutionary psychopathology is concerned with understanding physical and mental health-related disorders through evolutionary principles. The symptoms caused by microbial parasites such as viruses, bacteria, fungi and protozoa can be viewed as adaptations either of the pathogen to aid its multiplication or of the host in order to kill off or expel it. Evolutionary explanations for current-day physical and mental symptoms include the notion that our bodies and minds are adapted to the pressures of a stone-age existence but are living under modern-day conditions – the mismatch or time lag argument. Other explanations include the idea that genes which cause illness might also have positive facets associated with them – the pleiotropy argument; that selection pressures act on increasing inclusive fitness, not on perfecting systems – the compromise argument; and that disorders might be viewed as the extremes of normal variation – the trait variation argument.

By the mid-nineteenth century many scientists considered the notion of evolution seriously but the mechanism for this was lacking. In 1859 Charles Darwin introduced just such a mechanism – natural selection which is based on heritable variation and differential reproductive success. Hence individuals with characteristics which allow them to survive and outbreed others pass on such characteristics to future generations. The work of Williams, Hamilton and Trivers led evolutionists to reconsider the level at which selection operates. In The Selfish GeneRichard Dawkins made explicit the notion of the gene as the unit of selection and introduced the concepts of the replicator and the vehicle. The replicator is the gene and the vehicle the organism. Debates concerning individual versus gene selection continue. Generally, selection pressures which act on individuals will also act on genes directly. In the case of altruistic behaviour, however, this may not always be the case.

Comparisons with chimps, bonobos and gorillas reveal a number of substantial differences between apes and humans. Humans eat far more meat than primates, and, due to a lack of an oestrous swelling, a woman’s oestrus cycle is a mystery to men. Human infants require high parental investment. Neonate survival benefits from the lengthy pair bond that humans generally form. For long-term relationships both men and women look for loving and dependable partners who are in good health. Where the sexes differ lies in men’s greater emphasis on good looks and women’s preference for status and wealth. The reproductive strategy of an individual will depend on a number of factors such as the availability of suitable partners and the perceived attractiveness and age of a person. Evolutionary psychologists suggest that a woman’s mating strategy may be influenced by the nature of her parents’ relationship during her childhood.

In 1872 Darwin published The Expression of the Emotions in Man and Animalswhere he argued that there are a number of emotional expressions which are innate and common to all cultures – universal emotions. Such expressions include sadness, anger, surprise and enjoyment. The universality of human emotions is supported by three forms of evidence. Comparison with other primates suggests a common evolutionary ancestor; cross-cultural studies suggest that different cultures recognize and experience the same basic emotions; and certain areas of the human forebrain appear to be particularly associated with emotional states. Specifically, the amygdala and the orbitofrontal cortex. Negative states such as fear and anger may have evolved in order to place people in the correct psychological and physiological state to deal with aversive circumstances. Positive emotions such as love might serve the function of placing us in the appropriate psychological state to help build up social relationships.

Individual differences researchers investigate many kinds of psychological variation, but the most widely studied of these are personality and intelligence. Personality is defined in many ways, but one way of thinking of it is as a form of motivational system which predisposes people to seek out particular situations and respond in particular ways. Personality is measured most frequently by self-report questionnaires. These questionnaires usually describe a personality on a number of dimensions of factors (e.g. extraversion, neuroticism, psychoticism). Research using twin studies suggests that personality is moderately heritable. Theories developed to explain variation in personality have to account for both heritable and non-heritable components. It is necessary not only to understand why personality might be passed on through the genes, but also why so much of the variation in personality appears to be due to the environment. Various theories were advanced to explain both of these aspects of personality.

In 1871 in The Descent of Man and Selection in Relation to Sex, Darwin introduced the notion of sexual selection. Sexual selection leads to features that help individuals gain access to mates and takes two forms – intrasexual and intersexual selection. Intrasexual selection involves competition between members of one sex for access to the opposite sex, while intersexual selection involves members of one sex attempting to attract members of the opposite sex. In nature these forces are believed to lead to elevated levels of aggression, greater body strength and the development of attractive features in males. For females sexual selection leads to choosiness over mates. Sexual selection theory and the notion of female choice have recently become important concepts for the understanding of behaviour. There is now clear evidence from a number of species that female choice has been a driving force in the evolution of male adornment and aggressive behaviour.