By analyzing the strontium remaining in the tooth fossils of human ancestors, the researchers found that half of the female ancient apes came from far away during that period, while the male ancient apes grew up locally, the adolescent female ancient apes left their birthplace to mate and had children, while the male ancient apes lived in the place where they grew up  One possible explanation, the researchers say, is that related males are better able to defend against foreign invasion
Tooth composition can reflect the geographical environment of the area where teeth help people live
 And this also forces the male to become more scattered