ugnet_: Tanzanian Fossil May Trim Human Family Tree

[J Ssemakula]

February 21, 2003

Tanzanian Fossil May Trim Human Family Tree

A long-standing debate among scholars of human evolution centers on the 
number of hominid species that existed in the past. Whereas some 
paleoanthropologists favor a sleek family
tree, others view the known fossil record of humans as indicative of a 
tangled bush. The latter view has gained popularity in recent years, but a 
new fossil from Tanzania suggests that a
bit of pruning might be in order. Researchers writing today in the journal 
Science report that a specimen unearthed from Olduvai Gorge--a site made 
famous several decades ago by
Louis and Mary Leakey--bridges two previously established species, 
indicating that they are instead one and the same.

A team led by Rutgers University paleoanthropologist Robert Blumenschine 
discovered the fossil--an upper jaw with all of its teeth and the lower 
face. It dates to between 1.84 and 1.79
million years ago, around the time that our genus, Homo, was starting to 
come into its own in terms of evolving a larger brain, making tools and 
exploiting larger animals for food.
According to the report, the new find, dubbed OH 65, strongly resembles a 
fossil from Kenya attributed by some workers to the species H. rudolfensis. 
At the same time, however, key
features link OH 65 to the type specimen of the earliest known member of 
Homo, H. habilis. "OH 65 allows us to reshuffle the specimens that belong in 
the ancestral genus and tie
together rudolfensis and habilis," Blumenschine comments. "It shows that all 
three specimens are likely to be members of the same species--Homo habilis."

OH 65 and the stone tools and butchered animal remains that were found with 
it turned up in the drier, western part of the gorge. Based on the patterns 
of toolmaking and butchery
evident in the stones and bones, Blumenschine and his colleagues posit that 
hominids like OH 65 may have made "irregular, seasonal forays to the western 
basin streams from the
ecologically more productive southeastern basin," during wetter periods. If 
so, that would furnish additional support for the notion that even the 
earliest members of our genus were
behaviorally flexible, migrating in response to seasonal shifts in resource 
and shelter availability. --Kate Wong

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