What made early humans migrate to extremely cold places such as Russia to Alaska?

Question

What made early humans migrate to extremely cold places such as Russia to Alaska?

In: Other

Answer 1

Here are possible explanations:

* Parasites. Humans are from Africa, so naturally Africa has the largest number of specific human parasites in the world. Including malaria, African trypanosomiasis and other deadly illnesses.
* Enemies. Nobody wanted to take land from northern people until 19 century.
* Inability to leave. Once they came to areas that have almost no resources, they could not move further or return. This is the least probable reason, because humans somehow managed to move from Asia to America.