Wednesday, May 17, 2006
New meaning to "kissing cousins"
Chimpanzee and human ancestors may have interbred
By Michael Hopkin
The evolutionary split between humans and our nearest evolutionary cousins, chimpanzees, may have occurred more recently than we thought, according to a new comparison of the respective genetic sequences. What's more, it might have been a messy divorce rather than a clean break — leading to the controversial theory that our two sets of ancestors may have interbred many thousands of years after first parting company.
The discovery also casts doubt on the status of fossils that were thought to represent the first flowering of the human branch of the evolutionary tree — but which now may have to be reclassified as coming from a time before our split with the rest of the apes.
Previous estimates put the split at as much as 7 million years ago — meaning that Toumaï, a fossil dating from at least 6.5 million years ago in Chad and assigned to the species Sahelanthropus tchadensis, was hailed as the earliest-known member of the line that gave rise to modern humans.
But researchers led by David Reich of Harvard Medical School in Boston, Massachusetts, now calculate that the split may have occurred no more than 6.3 million years ago, and possibly as recently as 5.4 million. That would make Toumaï older than the time of the split...
Posted by Kyle Lindsey at 11:06 PM