Why do humans go to war?

Hi Lloyd, Thanks for another thought-provoking, very informative video! Did you ever read 'Sex at Dawn' by Christopher Ryan and Cacilda Jethá? It is not a very well-written book, in my humble opinion, and focuses way too much on sexuality. However, they argue very well that in primates that have similar dimorphism to humans, i.e., 15-20% larger males than females, reproductive success is most strongly determined by 'sperm-competition'. According to them, physical combat is (more) reserved to primates where that size-difference is much larger, such as Gorillas. Bonobos and chimpanzees, to which we are genetically closer, also depend on sperm-competition. Some arguments: Humans, like bonobos and chimpanzees, have large numbers of sperm cells for every ejaculation, whereas gorillas have manifold less. They also argue about the design of the male member can remove cells that were previously deposited (causes back-pressure). Also, the rise of monogamy correlates with an increase in male infertility these days, apparently. Food for thought ;-).