The effect is much larger than that. For most of the evolutionary history of humans, everyone* lived in Africa. Then only quite small groups left, taking with t

The effect is much larger than that. For most of the evolutionary history of humans, everyone* lived in Africa. Then only quite small groups left, taking with them only a small fraction of the genetic diversity of humans. Even today, the great majority of genetic diversity among living humans is inside Africa. (* who mattered. There were earlier migrations of hominids, but the mark they left on our genetics is much smaller than the influence from later migrations.)