This study also found that the large Mindoro forest mouse was the only "Apomys" species that displayed deep within-species divergences, which were calculated to date back some 400.000 years. The split between the large Mindoro forest mouse and the Luzon montane forest mouse dates back further still at an estimated three million years ago, putting it in the Pliocene. "Apomys" itself in turn was found to date back more than four million years, while the "Chromotys" division was estimated to go back another two million years. These dates were all calculated using a molecular clock.