The development of a baby's brain relies on the supplies of fat held in its mothers thighs and buttocks, according to science.
Professors William Lassek and Steven Gaulin from the University of Pittsburgh have been studying bottoms and believe their findings could explain why women are traditionally curvier than their male counterparts.
In an interview with the Sunday Times (£), Prof Lassek explains that fats in these areas are utilised particularly during breastfeeding and may affect intelligence.
You need lots of fat to make a nervous system and the fats in these areas are also enriched in DHA [docosahexaenoic acid] which is a particularly important component in the human brain.
It looks as if women have evolved to accumulate these fats and hold on to them — until a baby arrives.
- Prof Lassek, University of Pittsburgh
Prof Lassek points out that in most mammals, levels of fat in the body are around 5-10 per cent, but in women this number rises to 30 per cent - around the same as a "bear going into hibernation" or "whales living in cold Arctic seas".
David Bainbridge, a professor at Cambridge University, has backed up these findings in his new book Curvology: The Origins and Power of Female Body Shape.
He says that this phenomena has also affected the type of women that men have evolved to be attracted to - those with curvier hips are likely to give birth to healthier and more intelligent babies - although he does also admit other factors come into it.