The 'implication' that seems to worry people most of all is so-called 'genetic determinism'. It's the notion that, if human nature was shaped by evolution, then it's fixed and so we're simply stuck with it — there's nothing we can do about it. We can never change the world to be the way we want, we can never institute fairer societies; policy-making and politics are pointless.

Now, that's a complete misunderstanding. It doesn't distinguish between human nature — our evolved psychology — and the behavior that results from it. Certainly, human nature is fixed. It's universal and unchanging — common to every baby that's born, down through the history of our species. But human behavior — which is generated by that nature — is endlessly variable and diverse. After all, fixed rules can give rise to an inexhaustible range of outcomes. Natural selection equipped us with the fixed rules — the rules that constitute our human nature. And it designed those rules to generate behavior that's sensitive to the environment. So, the answer to 'genetic determinism' is simple. If you want to change behavior, just change the environment. And, of course, to know which changes would be appropriate and effective, you have to know those Darwinian rules. You need only to understand human nature, not to change it.

Margo Wilson's and Martin Daly's classic work on homicide illustrates this very clearly. Homicide rates vary enormously across different societies. When the rate in Chicago was 900 murders per million of the population per annum (for same-sex, non-kin killings) — this was in the 1970s and 80s — the rate in England and Wales was 30; and in Iceland there were hardly any murders at all. Now, there's no difference in the genes, no difference in human nature, in these places. And that shows up very dramatically when you look at the patterns of the murders. Although the rates are vastly different, the patterns are exactly the same. If you shrink the axes of the Chicago graph of the age and sex of the murderers and lay it over the England/Wales graph, the curves are an exact fit. It's overwhelmingly young men killing young men — starting, peaking and trailing off at exactly the same ages. What makes the difference to the rates is the different environments. And that's crucial for policy. We understand what it is about our evolved minds that leads to such different rates in different environments — the universal propensity of males to be highly competitive, which under extreme conditions can end up in homicide. And that tells us what conditions we'd need to create to lower the murder rates. Indeed, far from being 'genetic determinism', we can see why the Darwinian approach has even been called — with only a touch of irony — 'an environmentalist discipline'.