Born in Africa_ The Quest for the Origins of Human Life - Martin Meredith [31]
Having made its debut on the world stage, Zinj was taken to Johannesburg for a thorough evaluation, a task given to Phillip Tobias. He eventually concluded that Zinj was an australopithecine but one that merited a new species that he called Australopithecus boisei. The picture that emerged was of a stocky creature, robustly built, with wide cheekbones, mostly bipedal, but with a relatively small brain—no more than 530 cubic centimetres.
The full significance of Zinj, however, only came to light in 1961. In calculating its age, Leakey had estimated Zinj to have lived ‘more than 600,000 years ago’, a figure based on his assumption about the age of the volcanic ash in Bed I where the skull had been found. But such estimates were regarded at the time as amounting to little more than guesswork. No practical way of determining the absolute age of volcanic material and the ancient fossils they contained had yet been devised. Although radiocarbon-dating techniques had been in use since the early 1950s, they had proved to be unreliable when applied to material beyond about 30,000 years old.
In the late 1950s, however, a geophysicist from the University of California at Berkeley, Jack Evernden, developed a new method of radiometric dating known as potassium-argon dating. Evernden twice visited Olduvai to collect samples of tuffs and basalt; and his colleague Garniss Curtis took further samples in 1961. The results of their tests were announced in Nature in 1961. To general astonishment, they showed that the basalt in Bed I—and hence the age of Dear Boy—was around 1.75 million years old.
CHAPTER 6
HANDY MAN
A GOLDEN AGE of exploration followed the discovery of Zinj. The scientific community was by now generally agreed that Africa rather than Asia was the most likely birthplace of humankind. Inspired by Louis Leakey’s publicity campaign and by television programmes about Zinj, popular interest in human origins soared. A new generation of students took up the cause of palaeoanthropology. Funds for more fieldwork were readily available.
At Olduvai, the Leakeys were able to construct a permanent camp for the first time, to recruit full-time African staff and to invite specialist scientists to assist them. Mary spent most of her time there directing excavations, making only short visits to Nairobi. Louis was preoccupied with his work as curator of the National Museum in Nairobi and with numerous other projects and joined her for weekends and vacations. Each year he conducted long lecture tours in the United States, thrilling American audiences with impassioned accounts of his work on human origins and raising more funds. ‘As the years passed’, wrote Mary in her memoirs, ‘his reception in at least some parts of the States turned to outright hero-worship’.
The 1960 season at Olduvai proved highly productive. In May, the Leakeys’ nineteen-year-old son, Jonathan, wandering off on a fossil hunt of his own, discovered a fragment of the mandible of a sabre-toothed cat lying on the surface about 100 yards from the Zinj site. Hoping to find further remains, Jonathan sieved through surface deposits. Nothing more of the cat turned up, but he found instead a hominid tooth and toe bone. With growing excitement, a new excavation was started at what became known as ‘Jonny’s site’. In August, Mary uncovered fourteen foot bones there—the first discovery of the foot of an early human. In the following weeks, ‘Jonny’s site’ yielded remains from several different specimens—hand bones, parts of a skull and a lower jaw complete with thirteen opalescent teeth. The skull bones appeared distinctly different from those of its neighbour Zinj: They were thinner; the braincase was larger; there was no sagittal