Born in Africa_ The Quest for the Origins of Human Life - Martin Meredith [47]
With so much evidence of animal prints to hand, Mary’s team began to keep a lookout for any sign of hominid prints. In September, researchers spotted what looked like a hominid trail at Site A—four prints bearing the characteristic trace of a humanlike big toe. Initially, Mary remained sceptical, but after further study during the 1977 season, she concluded that they were indeed hominid. In February 1978, she announced her finding to the world at a Washington press conference. Several experts expressed doubts at the time, but later in the year, as the hunt for hominid prints continued, Mary Leakey was to achieve a spectacular success.
At his laboratory at the Cleveland Museum of Natural History in Ohio, Donald Johanson began the task of analysing the remarkable collection of Hadar bones he had brought back from Ethiopia. The haul included Lucy and the First Family and, in all, amounted to 350 separate fossil pieces from males, females and juveniles dating back 3 million years.
To help him with the analysis, Johanson invited Tim White to join him in Cleveland. Knowing that White was in possession of casts from the Laetoli fossils that he had been describing for Mary Leakey, Johanson asked White to bring them with him so that a comparison could be made with the Hadar fossils.
When making his first assessment of the Hadar fossils, Johanson had assigned Lucy as an australopithecine and the First Family as Homo. Lucy was different from the others, he had decided; she was much smaller, more primitive, with only a tiny brain. The notion that the First Family fossils belonged to Homo had been reinforced in 1976 when archaeologists working in a gully three miles from the main camp in Hadar discovered stone tools that were dated as 2.5 million years old—the oldest known stone tools in the world. Johanson assumed that only Homo could have made them.
In Cleveland, White argued that Lucy and the First Family belonged to the same species. The reason for the difference in their size, he suggested, was sexual dimorphism: females were smaller than males of the same species. What both noticed was that the Hadar fossils and the Laetoli fossils, though taken from sites a thousand miles apart and separated in age by more than half a million years, seemed decidedly similar.
By the end of 1977, Johanson and White had reached an agreed position. They concluded that there was compelling evidence to place not only Lucy and the First Family within the same species but Mary Leakey’s Laetoli fossils as well. Although markedly different in size, they were morphologically alike. At one end was Lucy: little more than three feet tall, probably weighing about sixty pounds; at the other end were individuals five feet tall, weighing up to 150 pounds. But all were said to be members of a single bipedal species.
Johanson and White also decided to classify the Hadar-Laetoli fossils as belonging to Australopithecus rather than Homo because they lacked an enlarged brain—the hallmark of the genus Homo—while possessing many characteristics common to australopithecines. But because several features—such as the more primitive teeth—differed from other known australopithecines, they believed it necessary to create a new species that they called Australopithecus afarensis.
As both Johanson and White knew, all this was bound to provoke controversy. No new hominid species had been created since Louis Leakey had named Homo habilis thirteen years before, triggering uproar. But the two Americans decided to go even further: to rearrange the entire family tree. The most widely accepted family tree in the 1970s showed Australopithecus africanus as ancestor both to Australopithecus