Molecular clock
Several lorises are found in the Siwalik deposits of Pakistan, dating to 16 to 8 mya, including "Nycticeboides" and "Microloris". Most are small, but an unnamed form dating to 15–16 mya is comparable in size to the largest living slow lorises. Molecular clock analysis suggests that slow lorises may have started evolving into distinct species about 10 mya. They are thought to have reached the islands of Sundaland when the Sunda Shelf was exposed at times of low sea level, creating a land bridge between the mainland and islands off the coast of Southeast Asia.