Why do humans immigrate to Africa?

In the long process of human evolution, * * * always went out of Africa three times, and the ancients who went out of Africa twice before were extinct. But the ancients who went out of Africa for the third time, that is, all the ancestors of human beings now, had genetic communication with these extinct humans to some extent. For example, our genome contains the DNA imprint of Denisova and the DNA of Neanderthals. For example, 2.4% of the entire genome of modern people comes from these extinct races, and the remaining 97% comes from Africa.

The network of human evolution in the old world is very complicated. It went out of Africa three times and exchanged genes among different races. However, the human evolution in the New World (America) is clear and clear, which is indisputable for a long time. Scientists have always believed that the existing Native Americans (Indians) migrated to North America from the Bering Strait about 654.38+0.5 billion years ago. At this time, the earth's climate was in the late Pleistocene Ice Age, and the Bering Strait was covered with a thick layer of ice because of its cold climate, so the ancients living in Asia were able to migrate to America.