PNAS will soon publish a paper from Mike Bruford and colleagues who isolated DNA from gorilla hair and feces and ultimately came up with a conclusion that the modern genetic composition of gorilla populations varies across different parts of their current geographic range and that this variation may be tied to Ice Age climate change and river barriers.
If that doesn’t make much sense, let me explain how such a situation would create genetic differences. During climate change between ice ages, populations that were in higher latitudes, found themselves separated physically because ice barriers formed and then collapsed, ultimately this segregated populations from one another another. Likewise, in drier climates, the tropics expanded and contracted to create isolated pockets much like what is created ice barriers. Ultimately these physical entities separated populations from one another. Also the genetic differences between gorilla populations is explained, in part, by the distance gorillas need to travel around river barriers, since in common with other large primates, they cannot cross large rivers.
Bruford comments on how this current study of gorilla population genetics is a crucial consideration,
“given the current catastrophic decline of great apes throughout Central Africa, current climate change patterns and the need to develop strategies to protect remaining populations from extinction.”