The closest relatives of gorillas are chimpanzees and humans, all of the Hominidae having diverged
from a common ancestor about 7 million years ago. 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. 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. There is
now agreement that there are two species with two subspecies each. 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. Primatologists continue to explore the relationships between
various gorilla populations.The species and subspecies listed here are the ones upon which most
scientists agree.[citation needed]
The proposed third subspecies of Gorilla beringei, which has not yet received a trinomen, is the
Bwindi population of the mountain gorilla, sometimes called the Bwindi gorilla.
Some variations that distinguish the classifications of gorilla include varying density, size, hair color,
length, culture, and facial widths. Now, over 100,000 western lowland gorillas are thought to exist in
the wild, with 4,000 in zoos; eastern lowland gorillas have a population of 4,000 in the wild and 24 in
zoos. Mountain gorillas are the most severely endangered, with an estimated population of about
620 left in the wild and none in zoos. Physical cha