 Researchers have proposed that the regional environment transitioned from humid jungle to more arid grasslands due to tectonic uplift and changes in broader patterns of ocean and atmospheric circulation.This environmental change is believed to have forced hominins to evolve for life in a savannah-type environment.Some data suggest that this environmental change caused the development of modern homimin features; however there exist other data that show that morphological changes in the earliest hominins occurred while the region was still forested.