Genetic Consequences of Warfare

Given the current limitations on our ability to understand the evolutionary impact of ancient warfare, are evolutionary inferences currently somewhat limited? What should be the most obvious but in fact is often overlooked are the differences between males and females that are likely attributable to their different roles in warfare.

There are alleles for a few genes that might have had their frequencies selected due to warfare. The most obvious and famous is the unfortunately named ‘warrior' gene. No studies of such potential genetic impacts have been taken very far, and none to my knowledge has looked at such genes through time using ancient DNA. This is an area of research that is likely to see great changes in the not too distant future. We can hope that the researchers will be careful in their interpretations and that society in general is sophisticated about such research and does not condemn it out of hand for failing to be ‘politically correct'.

Another question is to what extent is warfare rational, innate or irrational? Overall, we find several lines of evidence for very rational behaviour in leaderless warfare; for example, there is evidence that warfare can end quite abruptly when conditions change. In particular, the intensity of warfare does correlate with climate. This is best seen in the archaeological record where there is significant time depth. A very good example is from North America. Here, conditions favouring population growth seem to have existed during the Medieval Warm Period, and the carrying capacity appears to have been substantially reduced during the subsequent Little Ice Age. The result was a great increase in warfare over most of the continent, with a population crash in the American south-west and with intense warfare in the south-east that involved large, empty buffer zones between polities.^[77] Thus, we have evidence that some component of warfare is innate based on different genetic propensities between men and women best explained by male-focused war­fare as discussed above; some is rational as we can see from the climate change data, and we all know of its irrational aspects.