A Billion Years of Sex Differences by Steve Stewart-Williams review – what we get wrong about men and women

A psychologist wades into controversial territory in this counterintuitive study of nature, nurture and gender

According to the evolutionary psychologist Steve Stewart-Williams, almost everyone gets sex wrong. Traditionalists tend to exaggerate the natural differences between men and women. Progressives tend to minimise them, and to assume that nurture and socialisation play a decisive role. He wants to promote a more nuanced, scientifically rigorous public conversation about why and how men and women differ to guide better policymaking.

Some sex differences are relatively pronounced, he claims, such as whether you’re primarily attracted to men or women, upper body strength, height, the likelihood you’ll murder someone and occupational interests. Many, such as ability in maths, or conscientiousness, are much more modest. Such differences are best visualised as two overlapping bell curves. To illustrate this, consider height: the shortest humans are almost all women, the tallest are men, the average man is taller than the average woman, but there is considerable common ground. Knowing that someone is 5ft 8in won’t enable you to guess with any confidence whether they are a man or a woman, for instance.