Friday, May 28, 2010

Out of The Woods For 'Ardi'?

A palaeoblog tip of the hat to Howie Post, creator of Anthro (here inked by Wally Wood), who passed away earlier this month.
Ardipithecus ramidus – a purported human ancestor that was dubbed Science magazine's 2009 "Breakthrough of the Year" – is coming under fire from scientists who say there is scant evidence for her discoverers' claims that there were dense woodlands at the African site where the creature lived 4.4 million years ago.

Instead, "there is abundant evidence for open savanna habitats," says University of Utah geochemist Thure Cerling, lead author of a critique published as a "technical comment" in the Friday, May 28 issue of Science.

The criticism – by eight geologists and anthropologists from seven universities – is important because the claim that the 4.4-million-year-old fossil nicknamed Ardi lived in woodlands and forest patches was used as an argument against a longstanding theory of human evolution known as the savanna hypothesis.

That hypothesis holds that an expansion of savannas – grassy plains dotted with trees and shrubs – prompted ape-like ancestors of humans to descend from the trees and start walking upright to find food more efficiently or to reach other trees for shelter or resources.

In December, Science named the research that uncovered Ardipithecus and her environment as the 2009 "Breakthrough of the Year," citing how the fossils were more than a million years older than those of the previously oldest known hominid partial skeleton – that of Lucy, or Australopithecus afarensis.

But a month earlier, in November, Cerling and the seven other scientists submitted their critique to Science. The journal didn't publish it until now – when Cerling and his University of Utah coauthor, geologist Frank Brown, are in the field in Kenya and difficult to reach. Both expressed frustration it took so long.

The critique concludes that Ardi most likely lived in tree or bush savanna with 5 percent to 25 percent of the area covered by trees or shrubs, not the minimum 60 percent to meet the definition of a closed-canopy woodland. Cerling acknowledges Ardi could have lived in a wooded river corridor, but it was a river that flowed through savanna. link

Follow the debate here:

Comment on the Paleobiology and Classification of Ardipithecus ramidus

Response to Comment on the Paleobiology and Classification of Ardipithecus ramidus

Comment on the Paleoenvironment of Ardipithecus ramidus

Response to Comment on the Paleoenvironment of Ardipithecus ramidus