I think it is accurate to say that increased testosterone increases levels of violence. This can be shown in humans as well as other social mammals, in particular closely related species like rhesus monkeys, baboons, and chimpanzees.
Here's a paper about violence, testosterone, and humans:
Pubmed
Levels of testosterone also seems to have an effect on reproductive success in mammals.
Pubmed
quote:
We used a blinded, sham treated and self-controlled, randomized, multi-treatment crossover design to test the hypothesis that male sexual behaviour is regulated by oestrogen modulation of the serotonergic system in intact male Japanese macaque.
Sounds pretty scientific to me. So if male sexual behavior is regulated by hormones which in turn are created by genes, then I think it is safe to say evolutionary processes act on them.
I don't really know where to go with this, I'm not a good enough a writer to tie it all together. I suggest you search Pubmed for testosterone and you will find a lot more on the subject. I've been reading some books by professors Melvin Konner and Robert Sapolsky who cover a lot of this stuff. Look them up if you're interested. The interaction between genetics, the brain, environment, and behavior is absolutely fascinating.
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