I have a planet I'm working on which is inhabited by war tribes. They fight all the time. They can hunt and farm a little bit but they mainly fight to the death. There are billions of these beings on this planet (they reproduce quickly). I figured I can only keep them fighting if there was nothing in between them, mainly water.
Would a large rock world with a few large lakes be sustainable for life?
I want them to look grey and smaller than normal humans but not be dwarfs. I need a reason for somewhat intelligent beings to look grey. How can they evolve to be grey?