It is now widely accepted that the species Homo sapiens originated in Africa and eventually spread throughout the world. But did those early humans interbreed with more ancestral forms of the genus Homo, for example Homo erectus, the "upright walking man," Homo habilis, the "tool-using man" or Homo neanderthalensis, the first artists of cave-painting fame?
Direct studies of ancient DNA from Neanderthal bones suggest interbreeding did occur after anatomically modern humans had migrated from their evolutionary cradle in Africa to the cooler climates of Eurasia, but what had happened in Africa remained a mystery until now.
In a paper published in the Proceedings of the National Academy of Sciences, or PNAS, a team led by Michael Hammer, an associate professor and research scientist with the UA's Arizona Research Labs, provides evidence that anatomically modern humans were not so unique that they remained separate.
"We found evidence for hybridization between modern humans and archaic forms in Africa. It looks like our lineage has always exchanged genes with their more morphologically diverged neighbors," said Hammer, who also holds appointments in the UA's department ofecology and evolutionary biology, the school of anthropology, the BIO5 Institute and the Arizona Cancer Center.
Hammer added that recent advances in molecular biology have made it possible to extract DNA from fossils tens of thousands of years old and compare it to that of modern counterparts.
However, "We don't have fossil DNA from Africa to compare with ours," he said. "Neanderthals lived in colder climates, but the climate in more tropical areas make it very tough for DNA to survive that long, so recovering usable samples from fossil specimens is extremely difficult if not impossible."
"Our work is different from the research that led to the breakthroughs in Neanderthal genetics," he explained. "We couldn't look directly for
|Contact: Daniel Stolte|
University of Arizona