dybmh
ויהי מבדיל בין מים למים
I think you might be misunderstanding the underlying mechanisms behind Evolution. It is mutation and natural selection.
The organism won't develop something (like anger) simply because it would serve a purpose (to prepare the body for a physical enconter, for example), but rather what happens is that a mutation might entail a trait that proves beneficial to increase the survivability of an organism and the offspring have a certain likelihood of inhereting those traits.
Agreed! So, primate-A with anger-mutation has an advantage over primate-B lacking anger-mutation in a conflict over resources or procreation.