Oxygen and silicon make up most of earths crust
This question is unfortunately incomplete. However, the general skull features of <em>H</em><span><em>omo heidelbergensis </em></span>include large brow ridges, a broad, sloping forehead and a rear skull wall that is vertical rather than rounded or sloping.
Answer:
Tropical areas are warm and wet causing for animals to want to hide essentially. Also there is a lot of cover for animals to hide in. Usually in tropical areas there are a lot of predators also, another reason for animals to hide.
C... an animal that is faster than the others will have way better chances of survival. Thus, the animal with the mutation will pass on the trait more
