Evolution Theory Evolves Humans, Their Ancestors Coexisted 27,000 Years Ago, Study Says

Ancient ancestors of human beings survived far longer than scientists had believed, remaining in some places until as recently as 27,000 years ago and coexisting with modern humans over tens of thousands of years, according to new research being published today.

The finding lends strong support to a theory that various human ancestors spread through the world in a series of waves of expansion from Africa. Some scientists have long thought that our ancestors left that region in a single exodus, fanning out around the globe and evolving separately in different regions.

In a paper in Science, anthropologist Carl Swisher of the Berkeley Geochronology Center reports that new fossil dating techniques determined that Homo erectus, the first tool-using human ancestor, lived on the island of Java until as recently as 27,000 to 53,000 years ago - about a million years after that species died out in Africa.

Meanwhile, modern humans - Homo sapiens - apparently evolved in Africa and spread around the world, reaching southeast Asia and Australia 50,000 years ago or perhaps earlier. Thus, the two related species may have co-existed in the same region for 25,000 years or more, although there is no evidence yet that they ever came into contact.

The work by Swisher and his colleagues adds to a series of findings over the last few years that have blown a hole in the old view that human evolution was a steady, linear progression in which no two hominid species existed at the same time. Last year, new evidence showed that different early human ancestors existed simultaneously millions of years ago in Africa and in Asia. But Swisher’s work brings such coexistence far closer to the present time than ever before.

As an accompanying article in Science describes it, the emerging complexity of human evolution has transformed the prevailing view from “a simple and lonely tale of one species living at one time and evolving gradually into another species” into a tale that “has become thick with new subplots and characters.”

In addition, the new dating for the Java fossils - made possible by new, high-tech dating techniques based on analysis of different forms of chemical elements in the sample - show that Homo erectus also overlapped with Neanderthals, hominids far more advanced than they but more primitive than modern humans. Thus, according to Chris Stringer of the Natural History Museum in London, “if the dates are right, we have three different species coexisting at the same time.”