The people of Melanesia have a distinctive ancestry. According to the Southern Dispersal theory, a number of human beings emigrated from Africa between 50,000 and 100,000 years ago and dispersed along the southern edge of Asia. For some, the endpoint of this ancient migration was the ancient continent of Sahul, a single land mass comprising both the areas that are now Australia and New Guinea. (At that time, they were united by a land bridge, because sea levels were lower than they are now.) The first migration into Sahul was over 40,000 years ago. Some migrants settled in the part that is now New Guinea, while others continued south and became the aboriginal inhabitants of Australia.