Then, in 1959, came the now-famous discovery, in Olduvai, of a 1.75-millionyear-old skull that Leakey named Zinjanthropus boisei, and which he asserted was the “connecting link between the South African near-men . . . and true man as we know him.” The skull was similar to those of the robust ape-man creatures that had been found in South Africa, but differed from them in having heavier bones and bigger teeth. Nearly three decades of work had at last been rewarded, it seemed, and the huge publicity surrounding the find propelled the Leakeys—particularly Louis, though Mary had actually discovered the skull—to still greater fame.
Louis embarked on a speaking tour in the United States and Europe, and established a long and close relationship with the National Geographic Society, which publicized the Leakeys often in its magazine and provided them with financial support. In November 1960, 19-year-old Jonathan, the eldest of the couple’s three sons, made a discovery that was even more important than Zinjanthropus. Working near the Zinj site, he found a jawbone that was even more humanlike. It came to be known as pre-Zinj, because it was unearthed from deeper sediments and presumed to be older than Zinjanthropus. (Leakey later reclassified Zinjanthropus as an australopithecine; it is now generally known as Paranthropus boisei.)
In time, and as the Leakey team uncovered more fossil material, Louis became convinced that pre-Zinj was the ancient species of Homo he’d been seeking for so long. It had a bigger brain and was less ruggedly built than the socalled ape-men. He called it Homo habilis, or handy man, a reference to the stone tools at the site that Leakey was convinced the creature had made, and he believed it to be the ancestor of modern humans, Homo sapiens.
In 1964, Leakey and two coauthors submitted their findings on Homo habilis to the journal Nature. The response was fast and largely furious. Anthropologists dispatched condemnatory letters to the London Times and scientific journals. Their message: pre-Zinj was nothing more than an australopithecine, not a separate species of Homo. Part of the criticism was that in naming the new species, Leakey brashly changed the definition of Homo so that pre-Zinj would qualify. For example, at the time, a species of ancient human could be called Homo only if its brain were at least 700 cubic centimeters in volume. By this standard, pre-Zinj was something of a pinhead, with a brain of just 675 cubic centimeters (the average human brain has a volume of 1,300 cc).
Other discoveries that Leakey made in the 1960s also generated controversy. On an island in Lake Victoria, he found fossil evidence of two new primate species that he said pushed back the origins of human beings by millions of years. His claims were immediately met with harsh criticism. He called the primates Kenyapithecus. One species was 20 million years old. He named it africanus and claimed that it was the oldest hominid ever found. Experts disputed the claim then, arguing that it was a fossil ape, which remains the prevailing view. The other species, Kenyapithecus wickeri, was some 14 million years old. Its pedigree is checkered. Leakey first said it was more ape than human, but later modified that view. Scientists now believe that it is the most advanced fossil ape of its period in East Africa.