 An even smaller group, estimated at no more than 20 Chukchis, crossed what is now the Bering Sea approximately 13,000 years ago during the last glacial period, and migrated into North America.They are the ancestors of Native Americans, and 800 years later, they had reached as far as South America.The African diaspora is believed to have begun some 50,000 years ago, long enough for many changes to have occurred in humans remaining in Africa.