Evolutionary Psychology

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Simply put: Evolutionary psychology is the combination of two sciences - evolutionary biology and cognitive psychology.

The goal of research in evolutionary psychology is to discover and understand the design of the human mind. Evolutionary psychology is an approach to psychology, in which knowledge and principles from evolutionary biology (i.e. Darwin) are put to use in research on the structure of the human mind. It is not an area of study, like vision, reasoning, or social behaviour. It is a way of thinking about psychology that can be applied to any topic within it. Therefore, evolutionary psychology should be able to explain all aspects of human behaviour.

Biological evolution refers to the increasing changes that occur in a population over time. These changes are produced at the genetic level as organisms' genes mutate and/or recombine in different ways during reproduction and are passed on to future generations. Sometimes, individuals inherit new characteristics that give them a survival and reproductive advantage in their local environments; these characteristics tend to increase in frequency in the population, while those that are disadvantageous decrease in frequency. This process of differential survival and reproduction is known as natural selection. Non-genetic changes that occur during an organism's life span, such as increases in muscle mass due to exercise and diet, cannot be passed on to the next generation and are not examples of evolution.

There are essentially two factors that can account for differences in people: genes and the environment. This is sometimes called “nature” and “nurture” because your genetic make-up is determined by biology (hence nature), whereas your environment is controlled principally by other people and your environment (hence nurture). Evolutionary psychology places an importance on genes and biology in affecting behaviour. However, it does not reject the importance of the environment and appreciates that there is an interaction between genes and the environment.

We have evolved into humans over millions of years, and it is possible that some aspects of our behaviour have arisen through evolution. Evolution has been defined as 'the process by which new species arise as the result of gradual changes to the genetic make-up of existing species over long periods of time'. Darwin's (1859) theory of natural selection states that in each generation of a species not all individuals will survive, and that those that survive and pass on their genes to the next generation are likely to have been better adapted to their environment than those that died. This means that over many generations the genetic make-up of a species changes in ways that make it increasingly well adapted to its environment.

A classic example of a characteristic that might be explained by natural selection is the long neck of the giraffe. Presumably, as the ancestors of the modem giraffe had to take food from the branches of tall trees, those with the longest necks were best adapted to the environment and so tended to survive. As the individuals with the longest necks in each generation survived and passed on the genes for long necks, over many generations there came to be more and more giraffes with long necks - i.e. the giraffe’s evolved longer and longer necks. The idea behind evolutionary psychology is that, like the giraffe's long neck, some human characteristics and behaviours may have developed through natural selection, and are passed on from one generation to the next through genes. Behaviours and characteristics that increase the ability of an individual to survive and reproduce are known as adaptive behaviours or characteristics

Evolutionary approaches have been applied to many areas in psychology. We can look here at two issues from an evolutionary perspective. It is widely accepted that some aspects of children's abilities and behaviour have been shaped by evolution. More controversial is the idea that some aspects of adult social behaviour, such as mate selection, are also influenced by evolution.

Examples of Adaptive Behaviour in Humans

Innate behaviour and abilities in children

One area where we can look for evidence of natural selection is in the abilities and behaviours of babies. From birth, babies will instinctively look for something to suck on, and show a preference for the company of other humans. Babies show a rooting reflex in the first few hours after birth. If a baby's cheek is brushed against a nipple or teat, the baby will automatically turn towards it, ready to suck. We know that these are innate rather than learnt behaviours because they are present in all babies and because they are present from birth. From an evolutionary perspective, both of these behaviours are likely to have evolved because they maximise the chances of being fed, and hence surviving to reproduce. Human children, like the young of other mammals, display curious and playful behaviour. From an evolutionary perspective, curiosity and play in childhood are adaptive because they help us lean about the world and develop skills that become useful later.

Humans and other higher mammals have a strong innate need to form attachments (i.e. bond) to others. Failure to form a secure attachment in childhood has serious psychological consequences. Bowlby (1969) proposed that the instinct to form attachments in infancy has evolved because attachment provides a child with a secure base from which they can explore and to return to for safety when they are threatened. This tendency to remain in proximity to the caregiver and to return to them when threatened is adaptive because it means a caregiver will be on hand to help, and possibly because it makes it harder for predators to take children.

Children are also born with certain abilities. From as soon as nine minutes after birth babies will focus their attention on objects resembling a human face. From an evolutionary perspective, the ability to focus on the caregiver's face is adaptive because it aids the formation of an attachment between infant and caregiver (as we have already established attachment is itself adaptive). It is also possible that the tendency of young babies to cry when switching attention from one thing to another is adaptive because it means that whenever the baby looks at something new the caregiver is alerted and can help the child examine the object that has attracted its attention.

Mate selection

Darwin (1871) suggested that one way in which natural selection takes place is by sexual selection. In many animal species males compete directly for females (for example red deer), and in a few cases females compete for males (for example sea horses). Because males can potentially fertilise large numbers of females and need to invest little time and effort in their part of the reproductive process, their priority is to fertilise a large number of females, choosing their mates on the basis of their availability and fertility. Females on the other hand invest far more in reproduction (in term of time and energy: e.g. 9 months pregnancy and also years of bringing up the child), therefore they have more to lose if they choose a poor mate. Furthermore, being a scarce resource they can be selective about their mates.

Evolutionary psychologists have used these ideas to explain some aspects of human mating behaviour. Some people have observed for example that men tend to be more promiscuous (i.e. loose) and less choosy than women. In one recent survey of students' sexual habits, for example, Buss and Schmidt (1993) found that males wanted more sexual partners, expected sex after knowing someone a shorter time and were less fussy about who they slept with as compared to females. Archer (1996) has suggested that further support for the idea of greater promiscuity in men comes from comparing gay male, lesbian and heterosexual relationships. According to Archer, lesbians are less promiscuous and form more stable relationships than heterosexuals, whereas gay men, at least prior to the advent of AIDS, tended to be more promiscuous and form less stable relationships than heterosexuals.

It has also been observed that men tend to value youth and physical attractiveness highly, whereas women tend to put more of a premium on signs of wealth and status. Buss (1995) looked at studies of mate selection across a range of cultures and concluded that this tendency is common to all human cultures. In evolutionary terms this makes sense because, in order to maximise the probability of reproduction, males should seek females who are young and healthy (hence best able to bear children). Females, on the other hand, can maximise the probability of reproducing and their child being well cared for by choosing an older, wealthy man who is in a good position to provide materially for her and the child.

Testosterone and Fatherhood

In the weeks immediately after the birth of a child, levels of testosterone in fathers drop by more than 30 per cent. This, apparently has an evolutionary function. Testosterone-deprived men are less likely to wander off in search of new mates to inseminate. They are also less aggressive, which is useful when there is a baby around. In one study, men were given a swaddled doll and played a recording of a crying baby. Within half-an-hour their testosterone levels had fallen.

That explains a lot. Testosterone soars when men undertake risky behaviour or exert themselves physically. Crudely speaking, cradling a baby is the chemical opposite of scoring a goal or driving a fast car. My cousin was right. Dads are risk-averse, and in a competitive work environment where swagger counts, they will often lose out. Before they have children, men are conditioned to value their contribution to society exclusively in terms of their job. Fatherhood involves a reordering not just