Gorillas are ground-dwelling, predominantly herbivorous apes that inhabit the forests of central Africa. The eponymous genus Gorilla is divided into two species: the eastern gorillas and the western gorillas, and either four or five subspecies. They are the largest living primates. The DNA of gorillas is highly similar to that of humans, from 95–99% depending on what is counted, and they are the next closest living relatives to humans after the chimpanzees and bonobos.
The closest relatives of gorillas are chimpanzees and humans, all of the Homininae 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.
Gorillas live in groups called troops. Troops tend to be made of one adult male or silverback, multiple adult females and their offspring.However, multiple-male troops also exist.A silverback is typically more than 12 years of age, and is named for the distinctive patch of silver hair on his back, which comes with maturity. Silverbacks also have large canine teeth that also come with maturity. Both males and females tend to emigrate from their natal groups. For mountain gorillas, females disperse from their natal troops more than males.Mountain gorillas and western lowland gorillas also commonly transfer to second new groups.Mature males also tend to leave their groups and establish their own troops by attracting emigrating females.