Sunday, April 10, 2005

Some new data about the earliest hominids

Carl Zimmer at the loom has a nice post about a few recent spectacular homid finds. The braincase of Sahelanthropus, a 7 million year-old fossil found in Chad, has been analysed, and is now definitively assigned to the hominid lineage. The locus of the find, well outside the rift valley regions in Ethiopia and Kenya, has caused some consternation for the camp which believes that Ethiopia is the cradle of hominid evolution. Possibly hominids dispersed far earlier than expected. Or, maybe the story is just too incomplete to judge.

Is it just me, or are these MRI scans of the braincases being given an awful lot of evidentiary heft? About two months ago, braincase scans of the hobbit skulls were also used to definitively assign homo floresiensis to a separate species. Don't get me wrong- the enlargement of the brain is the single most important feature definining the human lineage ( a nice review of recent findings is here ). But I get a bit nervous when everything's getting hung on a single hook. I'd be more comfortable when other fossils are found in Chad, for instance, or more hobbits.

See also John Hawks' weblog for a great writeup of the original Chad discoveries. Even if the braincase stuff doesn't hold for some reason, these are tremendously important fossils.

UPDATE: The New York Times also covers the Nature article. I had misunderstood the claims of the Nature paper: apparently they're asserting that the Chad fossils represent a common ancestors to chimps and humans exclusive of great apes.

No comments: