While much of Africa today features arid deserts, Western Africa and at least parts of Central Africa and Eastern Africa were rainforests and tropical forests during a key time of early hominin evolution. Humans and chimpanzees had a common ancestor that lived in Africa about 7.5 million years ago, likely in East Africa or perhaps Central Africa. Humans did not evolve from Chimpanzees, but both are the current evolution of a common ancestor. That common ancestor has yet to be identified and is sometimes referred to as the Chimpanzee–Human Last Common Ancestor (CHLCA). The descendants of CHLCA are known collectively as the Hominini tribe within the larger Hominidae family. Today this tribe includes only humans, the common chimpanzee, and bonobos.

Did you notice that I said CHLCA is not part of the Hominini tribe? Interestingly, scientists so far have rudely excluded the ultimate founder of the Hominini tribe. Tribes are defined by common characteristics and because we have yet to find a CHLCA, they are left out. However, I disagree with this and this is a great time to make a point about evolutionary science. Since all known descendants of CHLCA, living and extinct, have the common characteristics that define the Hominini tribe, so did CHLCA. For more on why the simplest explanation gets this kind of weight in analysis, check out my Occam’s Razor: Simplifying Complexity article.

CHLCA likely lived sometime between 5 and 13 million years ago, with 7.5 million years ago being a common educated estimate. Sahelanthropus tchadensis, and other later Hominini tribe descendants, supports estimates placing the CHLCA at about 7.5 million years ago. For example, Sahelanthropus tchadensis survived from 7 to 6 million years ago in Central Africa.