Evolution and classification

The closest relatives of gorillas are the other two Homininae genera, chimpanzees and humans, all of them having diverged from a common ancestor about 7 million years ago.

[12] Human gene sequences differ only 1.6% on average from the sequences of corresponding gorilla genes, but there is further difference in how many copies each gene has.[13] Until recently, gorillas were considered to be a single species, with three subspecies:

the western lowland gorilla, the eastern lowland gorilla and the mountain gorilla.[9][14] There is now agreement that there are two species, each with two subspecies. More recently, a third subspecies has been claimed to exist in one of the species.

The separate species and subspecies developed from a single type of gorilla during the Ice Age, when their forest habitats shrank and became isolated from each other.[1]

Primatologists continue to explore the relationships between various gorilla populations.[9] The species and subspecies listed here are the ones upon which most scientists agree.[15]