The people of Melanesia have a distinctive ancestry. Along with the aboriginal inhabitants of Australia, they are believed to derive from the Proto-Australoids who emigrated from Africa between 50,000 and 100,000 years ago and dispersed along the southern edge of Asia, giving rise to Australoid populations in various places, including South India, Sri Lanka, the Andaman Islands, the Philippines, and others. The limit of this ancient migration was Sahul, the continent formed when Australia and New Guinea were united by a land bridge as a result of low sea levels. The first migration into Sahul came over 40,000 years ago. A further expansion into the eastern islands of Melanesia came much later, probably between 4000 B.C. and 3000 B.C.