“War—what is it good for? Absolutely nothing. Say it again.” So runs the 1970 pop song that Edwin Starr made famous and that’s now the obligatory soundtrack for every documentary about the Vietnam antiwar movement. For the historians, anthropologists and economists who study warfare, it’s more complicated than that. The sheer ubiquity of war across time and place suggest that it must be good for something. Evolutionary biologists take a longer view. They pose the basic Darwinian question: Does success in warfare enhance reproductive success, increasing the number of copies of genes that a man passes to future generations? Spectacular examples of this certainly exist. Ibn Saud, who unified Saudi Arabia in 1932 after a series of conquests, has thousands of descendants; tens of millions of humans appear to carry the genes of Genghis Khan.
But is there more systematic evidence that high rates of participation in warfare enhance reproductive success? In the long arc of human evolution, the most successful men at being fruitful and multiplying are unlikely to have been successful warriors.