Human Evolution: Paranthropus boisei
Mary Leakey, the wife of Louis B. Leakey, discovered the first specimen of Paranthropus boisei, a well-preserved cranium, on July 17, 1959, at Olduvai Gorge, Tanzania (then Tanganyika). Louis was laid up in camp at the time with a fever. But, truth to tell, even if he had been in better shape, it's unlikely he'd have found it — Of the two, Mary did far more of the hands-on work of fossil discovery. Louis was the intuitive member of the pair. He picked the likely sites. Mary did most of the digging. Dating to 1.75 mya, the skull was the first robust australopithecine ever found and did much to convince the scientific world that Darwin and Raymond Dart had been right about their claims of Africa being the earliest scene of human evolution. A replica of the skull (and of a jaw found separately by Kamoya Kimeu in 1964) is shown at right. Initially, this hominid was assigned the name Zinjanthropus boisei, but was later renamed Australopithecus boisei. In recent years it has often placed in the genus Paranthropus, since it is one of the robust australopithecines (given the sturdy chewing-related features of its skull). The cranial capacity of Paranthropus boisei was 500-550 cc — about the same as that of a typical gorilla. Moreover, its skull exhibits various other gorillalike traits — a robust jaw, sagittal crest, heavy postcanine teeth, thick tooth enamel, and a flaring zygomatic arch (PICTURE OF GORILLA SKULL) — But the canines and incisors are similar to a human's (see figure at right). Paranthropus boisei is nicknamed "Nutcracker Man" because it has the largest molars of any known hominid, which is fairly obvious in the figure. Their grinding surface is over twice as large as that of a modern human. Males stood 1.3 meters (4 feet 3 inches) tall and weighed about 70 kilograms (154 pounds). Females weighed just 45 kilograms (about 100 pounds) and were only about 1.05 meters (3 feet 5 inches) in height. This hominid may have used shaped stone tools, albeit crude ones — little more than broken pebbles with sharp edges. However, this is controversial — the tools in question might have been the products of contemporaneous Homo. It is still uncertain how the paranthropines are related to modern humans. Some maintain they were our direct ancestors. But their contemporaneous existence with early representatives of the genus Homo casts this claim in doubt. (Indeed, given modern trends in evolutionary theory, it may well turn out that the best way to describe human evolution is in terms of a web rather than a tree.) Perhaps the greatest significance of Paranthropus boisei is that its 1959 discovery convinced the scientific world that the place to look for the earliest humans is Africa.
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