The BBC has a news report up gathering reactions to a new PLoS ONE paper, The Later Stone Age Calvaria from Iwo Eleru, Nigeria: Morphology and Chronology. This paper reports on remains found in Nigeria which date to ~13,000 years B.P. that exhibit a very archaic morphology. In other words, they may not be anatomically modern humans. A few years ago this would have been laughed out of the room, but science moves. Here is Chris Stringer in the BBC piece:
“[The skull] has got a much more primitive appearance, even though it is only 13,000 years old,” said Chris Stringer, from London’s Natural History Museum, who was part of the team of researchers.
“This suggests that human evolution in Africa was more complex… the transition to modern humans was not a straight transition and then a cut off.”
Prof Stringer thinks that ancient humans did not die away once they had given rise to modern humans.
They may have continued to live alongside their descendants in Africa, perhaps exchanging genes with them, until more recently than had been thought.
In the broad outlines most people still seem to hold that within the last ~100,000 years there was a major demographic pulse which swept out of Africa and populated the rest of the world. Something special did happen. Oceania and the New World were settled by the descendants of anatomically modern humans, whom we can trace back to Africa. The key modifications to the old model seem to be two-fold:
1) The possibility of admixture with other lineages on the way out
2) The sublocalization of the “Out of Africa” scenario, and further admixture with lineages within Africa
There have long been debates about an East or South Africa ur-heimat for the first anatomically modern humans. Others are now even positing a North African origin! To a great extent I wonder if a West or Central African origin is forgone in part due to the paucity of fossil remains entailed by the unfavorable conditions for preservation.
However the details shake out the story seems to be getting more, not less, complicated. This makes for less pithy one liners for the media, but also more work for scientists. Figuring out stuff can be fun!