Girls like pink better because in Stone Age times they needed to be good at picking berries and women have better sex with rich men - or so some evolutionary psychologists would have us believe.
Critics say this isn't science, but conjecture.
Evolutionary psychology seeks to explain human behaviour from the hunter-gatherers or our nearest relatives, the chimpanzee, and has some seductively simple theories.
One argument is that we have Stone Age brains in 21st-century skulls, from which we can account for everything from the violence that men show to their stepchildren to why racism exists.
Is evolutionary psychology a truly useful addition to the canon of ideas to come out of Darwinian evolution or a just-so science that can be adjusted to suit the researchers' prejudices?
Steve Jones examines the history of the new science, the methods used and asks if it can explain the human drive to language, religion and culture.