“From a scientific point of view, maybe the only people that you could consider not to be immigrants would be some Khoe-San-speaking groups in southern Africa,” said Austin Reynolds, an assistant professor of anthropology at Baylor University in Texas who specializes in human population genetics.

The designation Khoe-San (pronounced coy-sawn) refers to certain African communities in the areas of Botswana, Namibia, Angola and South Africa who speak similar languages with distinctive clicking consonants, Reynolds told Live Science.

Reynolds said there are two main factors indicating that Khoe-San groups may be non-migratory descendants of original humans: They live in the place where it’s likely humans first appeared, and they have a high amount of genetic diversity. A good way to understand why high genetic diversity indicates original ancestry is by comparing genes to a bowl of M&Ms, Reynolds said. Handfuls taken out of the bowl — i.e. people who broke off from the original human population — might have only a couple M&Ms colors in them, but the original bowl will have all the colors.