Born in Africa_ The Quest for the Origins of Human Life - Martin Meredith [56]
In the five weeks of excavation that followed, some 300 fossil fragments were recovered. Many were unidentifiable. But from the remainder, Johanson’s team managed to piece together parts of a skull, a palate with some worn teeth and small segments of both arms and legs, enough for Johanson to be able to claim ‘a partial skeleton’. What emerged, according to Johanson and White, was a creature smaller than Lucy, standing about three feet three inches, but with longer arms in relation to its legs. Because it was so small, they deduced that it was female. Although it was as apelike as Lucy, it was dated as being a million years more recent in time—about 1.8 million years.
After studying the lower jawbone and teeth, Johanson and White concluded that this creature—Lucy’s child, as it came to be known—was a specimen of Homo habilis. ‘We had found the first skeleton known of the earliest species of Homo’, Johanson claimed.
But naming Lucy’s child as a Homo habilis presented difficulties. The standard view was that Homo habilis was an intermediate species between australopithecines and Homo erectus. Yet Lucy’s child, although having the right age to be Homo habilis, possessed features more in common with Lucy, who had lived more than a million years beforehand. Indeed, the first detailed analysis of OH 62, as Lucy’s child was formally called, showed that on every measurement taken, OH 62 was even more apelike than Lucy. All this seemed to make nonsense of evolutionary principles.
There was a further conundrum. If OH 62 was a Homo habilis, then according to the lineage accepted by most palaeoanthropologists, this tiny apelike creature living 1.8 million years ago had given rise to Homo erectus—which Turkana Boy had shown to be a strapping sixfoot-tall species—all within the space of 200,000 years. The explanation given by Johanson and White was that there had indeed been a sudden change. ‘Something extraordinary was happening during those few hundred thousand years of evolution, some shift in behaviour that would quite suddenly transform a Homo with a comparatively small brain in a primitive body into one with a big brain’, Johanson wrote in Lucy’s Child. ‘An unprecedented evolutionary event had taken place’.
But others disputed this line of reasoning. Leakey and Walker believed that OH 62 was some type of gracile australopithecine, as yet unnamed. Part of the problem, they argued, was the way that palaeoanthropologists had turned Homo habilis into a wastebasket species, throwing in an odd assortment of fossils around 2 million years old, with a variety of morphologies and brain sizes.
Whatever classification was used, the fossil evidence was beginning to indicate to palaeoanthropologists that in the million years after 2.5 million years ago, there had been no simple linear transition from one species of Australopithecus to a successor species of Homo but rather a period of wild evolutionary experimentation.
Other scientists were coming to the same conclusion.
CHAPTER 12
A DANCE THROUGH TIME
WHILE STUDYING the fossil record of African antelopes and other bovids during the 1970s, Elisabeth Vrba, a South African palaeontologist working at the Transvaal Museum, discovered evidence of dramatic evolutionary change in their history that had occurred about 2.5 million years ago. In sudden profusion, new species had emerged; old ones had died out. The cause, Vrba believed, was a marked change in vegetation cover. Antelope species with a general diet—such as impala—survived by adapting to different vegetation; the same impala species had remained unchanged