I was wondering about what environmental factors contributed to human beings having the form, functions, etc. that we have now, specifically compared to our most recent non-Homo sapiens ancestor (arguably Homo heidelbergensis) and compared to Homo neanderthalensis. As an example of what I mean by "what factors" I'm going to resort to a non-human example of sexual dimorphism in animals. Where maybe a male bird ends up growing much bigger than a female because resources in a specific environment are concentrated in places, rather than spread out and so the males have to defend certain territory against other males and attract females through ownership of the resource. Whereas if the resources are spread out over an environment males may develop some sort of really glamorous tail (like a peacock) to attract females to it instead. I'm not asking about the things limited to sexual selection, but about all factors in general and how they shaped us. So, any thoughts? If possible, cite your sources.