Thursday, May 18, 2006

More primate (not monkey, darnit!) business

It may not have trickled its way onto most people's radars, but this provocative story has my corner of the internet all a-buzz:

Humans, chimps may have bred after split

Boston scientists released a provocative report yesterday that challenges the timeline of human evolution and suggests that human ancestors bred with chimpanzee ancestors long after they had initially separated into two species.

The researchers, working at the Cambridge-based Broad Institute of Harvard and MIT, used a wealth of newly available genetic data to estimate the time when the first human ancestors split from the chimpanzees. The team arrived at an answer that is at least 1 million years later than paleontologists had believed, based on fossils of early, humanlike creatures.

The lead scientist said that this jarring conflict with the fossil record, combined with a number of other strange genetic patterns the team uncovered, led him to a startling explanation: that human ancestors evolved apart from the chimpanzees for hundreds of thousands of years, and then started breeding with them again before a final break.

''Something very unusual happened," said David Reich, one of the report's authors and a geneticist at the Broad and Harvard Medical School.

The suggestion of interbreeding was met with skepticism by paleontologists, who said they had trouble imagining a successful breeding between early human ancestors, which walked upright, and the chimpanzee ancestors, which walked on all fours. But other scientists said the work is impressive and will probably force a reappraisal of the story of human origins. And one leading paleontologist said he welcomed the research as a sign that new genetic information will yield more clues to our deep history than once thought.

''I find this terrifically exciting and important work," said David Pilbeam, a Harvard paleontologist who was not part of the Broad team.

Aside from the fact that the headline is technically not true--neither humans nor chimpanzees as we know them were around at the time of this alleged breeding; it would be more accurate to say that members of the lineages that eventually led to modern humans and chimpanzees may have interbred after these lineages split (Alas, accuracy is once again sacrified in the name of sensationalism)--this is a fascinating story. Rather than offering my own under-informed opinions, let me point in the direction of two immensely more-qualified resources on this controversial topic: the fascinating commentary of science writer extraordinaire Carl Zimmer and the tempered criticisms of John Hawks, a Professor of Anthropology at the University of Wisconsin-Madison. Unless your curiosity drive is malfunctioning--in which case you should seriously consider taking it into the shop--and you are somehow already bored by this fascinating topic, check out the posts by these two writers; they're delicious brain-food.

Oh, and if any kind, Nature-subscribing Samaritan who stumbles onto this blog feels a pressing desire to email me ( a copy of the paper, I certainly would be obliged; I'd love to read this one.


Literacygirl said...

"led to modern humans and chimpanzees may have interbred after these lineages split "

Ew, ew, ew. I should have waited until after dinner to read this post.

Dave said...

I fail to see what is so disgusting about this idea. It's not like we're talking about actual humans and chimps breeding here. The alleged interbreeding--and I'm sure that the coming issues of Nature will be filled with pages arguing about whether or not this ever really happened--occured millions of years ago, between two groups that were probably pretty similar to each other (they'd have to be similar in order to interbreed). The genus Homo was not even existant at this point, much less the Homo sapiens that we all know and love.

It's an interesting hypothesis--one that I'll definitely be monitoring for new developments--but unless a person is opposed to the idea of human evolution from ape-like ancestors itself, there really shouldn't be anything here to offend anybody's sensibilities.