The correct answer is B) they migrated mostly overland from Africa over the last eighty thousand years.
The best explanation for how humans populated the Earth is "they migrated mostly overland from Africa over the last eighty thousand years."
Historians and anthropologists had done a lot of research on this subject and concluded that South Africa is "the cradle of humanity." Yes, scientists considered that humanity originated in the region of South Africa and from there, humans started to spread to other regions of the planet. They migrated to other parts of Africa and then they went to Asia.