Eastern gorilla
There are two recognised subspecies of eastern gorilla: the mountain gorilla ("Gorilla beringei beringei") of the volcanic slopes of Rwanda, Uganda and eastern Democratic Republic of Congo; and Grauer's gorilla or eastern lowland gorilla ("Gorilla beringei graueri") in eastern Democratic Republic of Congo.
Evolution of primates
Molecular evidence indicates that the lineage of gibbons (family Hylobatidae) diverged from Great Apes some 18-12 million years ago, and that of orangutans (subfamily Ponginae) diverged from the other Great Apes at about 12 million years; there are no fossils that clearly document the ancestry of gibbons, which may have originated in a so-far-unknown South East Asian hominoid population, but fossil proto-orangutans may be represented by "Sivapithecus" from India and "Griphopithecus" from Turkey, dated to around 10 million years ago.