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Early human skeleton apes its ancestors.

Early Human Skeleton Apes Its Ancestors

Homo habilis is considered to be thefirst truly human species and earliest tool user, appearing in southern and eastern Africa between 2 million and 1.6 million years ago, but you would not know it from the neck down. Now, the first limb bones clearly associated with skull fragments of a single. H. habilis individual have been found, report scientists in the May 21 NATURE. The remains suggest that members of the species had unexpectedly small, apelike bodies attached to the more delicate faces and larger brain cases typical of the Homo line.

The fossils, uncovered last summer inTanzania's Olduvai Gorge, belong to an adult female who had long, heavily built arms and stood somewhere between 3 and 3 1/2 feet tall, according to the 10-member scientific team. The project was directed by Donald C. Johanson of the Institute of Human Origins in Berkeley, Calif.

"What we see is a creature whose bodysize and anatomy are strikingly similar to Lucy's,' says anthropologist and expedition member Tim D. White of the University of California at Berkeley. "Lucy' is a 3.3-million-year-old partial skeleton discovered in Hadar, Ethiopia in 1974 by Johanson and White. Lucy is widely considered to be a female member of the first humanlike species, Australopithecus afarensis, which appeared around 4 million years ago and eventually gave rise to H. habilis. It is estimated that Lucy stood about 3 feet 8 inches tall.

The assumption of some paleoanthropologiststhat, beginning with A. afarensis, body size increased gradually along with brain size, appears to be mistaken, say Johanson and his colleagues.

The teeth of the partial skeleton are asbig, relative to body size, as Lucy's, say the researchers. Previous studies of isolated H. habilis remains concluded that the size of its cheek teeth had shrunk compared to the australopithecines.

The discovery that H. habilis had such aprimitive build 1.8 million years ago, combined with evidence of a taller and more modern-looking H. erectus 1.6 million years ago (SN: 10/27/84, p.260), points to an "abrupt transition' between these two species in eastern Africa, say the researchers.

The new specimen was identified byexamining the lower face bones and palate, including four teeth, and making comparisons to previously uncovered H. habilis skull fragments. Important information about the body came from measurements of a thigh bone and all of the bones of one arm.

Nevertheless, says anatomist BernardWood of Liverpool (England) University in the same NATURE, "the new find rudely exposes how little we know about the early evolution of Homo.' The species designation for H. habilis was first proposed more than 25 years ago, but it remains poorly represented in the fossil record.

Previous studies, says Wood, indicatethat there are two subgroups of fossils labeled H. habilis, one with large brains, teeth and jaws, the other with smaller brains and more lightly built faces. The new find, he says, does not resolve whether these subgroups represent males and females of one species or separate species.

White acknowledges that the issue isnot settled, but adds that the consensus among paleoanthropologists is for two sexes, not two species. "The same level of variation in size between the sexes at Hadar [the female Lucy as opposed to larger male specimens] characterizes the known habilis specimens,' says White. "A fundamental aspect of early hominid anatomy may be high levels of sexual dimorphism [size differences between the sexes].'

Characteristics other than size showthat H. habilis was a "mosaic creature,' he says, with facial anatomy evolving in the human direction and limb proportions like those of much earlier ancestors.

Photo: Homo habilis fossils found in Tanzania lastsummer.
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Title Annotation:Homo habilis limb bones found in Tanzania
Author:Bower, Bruce
Publication:Science News
Date:May 30, 1987
Words:609
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