Pin of darwin written inside a holy christian fish with legs and feet

Evolutionary explanations

Natural selection and Darwinian evolution are believed to be the main forces shaping life

An evolutionary approach can be used to try to understand sex differences, but it has its drawbacks.

Evolution by natural selection is a key principle of biology. It is based on the idea that selective pressures act on naturally occurring variations, so that those most suited to their environment do well at the expense of the less well-adapted.

So if there are biological sex differences, they should therefore have their origins in natural selection.

One assumption is that humans are adapted to a Stone Age life: we have developed culturally and socially so rapidly that natural selection simply has not had time to adapt our bodies (and we have also been able to remove many selective pressures through the use of medicine, better hygiene and so on).

Illustration showing early male and female roles and modern male and female roles
Did early male and female humans have well-defined roles? Has evolution selected for males with good visuospatial skills – all the better for hunting woolly mammoths? Are women naturally good carers and communicators? Or are gender roles simply a convenient division of labour that is culturally inherited?

Illustration © Glen McBeth

Sex differences can therefore be explained by selection for sex-specific roles useful in early human history (see the illustration). But although the theory can explain certain observations, it is very difficult to test experimentally.

Like sex differences, gender roles can be passed on from generation to generation, adapt to changing circumstances, and provide a survival advantage.

They may not be genetic, however, but culturally inherited – handed down through family or social traditions, storytelling, religion or formal education. It is tempting to see ourselves as Stone Age humans trying to cope with the modern world, mentally specialised to a hunting-and-gathering lifestyle. On the other hand, our brains may be flexible problem-solving devices able to adapt to a wide range of circumstances.

Lead image:

BobvdK/Flickr CC BY

About this resource

This resource was first published in ‘Sex and Gender’ in January 2006 and reviewed and updated in October 2014.

Genetics and genomics, Ecology and environment
Sex and Gender
Education levels:
16–19, Continuing professional development