Assertion: mountain gorilla's population | /r/HasProperty | separated by gradual drying of the region
Facets:
value: originally
type: OTHER
value: probably
type: DEGREE
Source sentences:
text: The western and eastern populations were probably originally separated first by the massive inland Congo basin lake of the Miocene, and then, from about 5 million years ago, by the gradual drying of the region and the retreat of forest to higher areas.