Evolutionary Explanations of Human behaviour (HL IB Psychology)

Evolutionary explanations for human behaviour

What is an evolutionary explanation for behaviour?

• Evolutionary psychology is part of the biological approach to explaining behaviour (based on Darwin’s theory) which explains how and why behaviours e.g. aggression, memory, language, partner preference are the products of natural selection

• Natural selection is the process whereby behaviours and traits which are useful for survival and reproduction are retained – and those which are not eventually die out

• Adaptive behaviours are those which increase the chances of survival and reproductive success which is why they are passed down through the generations i.e. how we behave now is the product of ultimate causes

What is an evolutionary explanation for partner preference?

• Evolutionary psychology proposes that males look for female partners who are young and who look healthy (e.g. clear skin, glossy hair) and fertile (e.g. wide hips)

• Evolutionary psychology proposes that females look for male partners who have resources (e.g. a good job, money, stability) and who will be able to provide a secure home for the children that the couple produce

• The theory of anisogamy states that females are more choosy than males when it comes to selecting sexual partners

• Female choosiness is based on the idea that ‘sperm is cheap; eggs are expensive’ i.e. men produce billions of spermatozoa on a daily basis but a woman produces only one egg per month

• A man may have sex (and impregnate) many women without much consequence but if a woman has sex there is always the chance that she will become pregnant, ergo she must be choosy as to who she has sex with as a male without resources is not good material as the potential father of her children

• A proximate cause of behaviour might be seen in a person showing jealousy and wishing to keep their partner close but an evolutionary ultimate cause of behaviour would say that this jealousy is based on a primeval fear of losing either the opportunity to continue one’s genetic line (males) or the protection afforded by a partner (females)

A sexist stereotype? Evolutionary psychology says no…

What are the flaws in an evolutionary explanation of partner preference?

• While it is true that there are plenty of examples of rich old man/pretty young woman couples, this is a reductionist way of explaining partner preference – and it encourages stereotyping and sexism too

• Some women prefer younger men, some men prefer older women; plenty of women are able to provide resources for themselves and their family; some women are not remotely interested in money; some men do not wish to have children

• This theory makes no accommodation for homosexuality, as it is purely focused on heterosexual partnerships

• There is no way of gathering empirical evidence to support this theory as it based on inferences drawn from observing proximal behaviours based on ultimate causes 

Which studies investigate evolutionary explanations of partner preference?

• Buss (1989) – a cross-cultural large-scale survey of attitudes towards partner preferences

• Clarke & Hatfield (1989) – a field experiment which investigated female choosiness in terms of partner selection

The studies by Buss (1989) and Clarke & Hatfield (1989) can be found in ‘Two Key Studies of Evolutionary Explanations for Behaviour’ on this site: just navigate the Genetics & Behaviour topic to find it