LOOKING FOR THIS NOVEL

So I don’t really remember much,but it’s a novel where it’s in ancient times and there are tribes. The MC is a male, and he helps build the tribe up. The tribesman know that inbreeding cause birth defects so other tribes gather to have children then dip back to their own tribe. Also there’s a part where a tribe try’s to sneak up on the MC tribe but they have destroyed all the trees in the area for firewood and more so the attack failed. That’s all i remember, sorry but thank you for the help.