Born in Africa_ The Quest for the Origins of Human Life - Martin Meredith [74]
The makers of these stone tools remain unidentified. No hominid fossils have been found at the sites, though parts of a 2.5 million year-old australopithecine—Australopithecus garhi—have been recovered near Gona. But in view of the skill the toolmakers at Gona applied, the origin of toolmaking clearly lies further back within the australopithecine world. Cut marks on bones found at Dikika in Ethiopia provide evidence of possible tool use as far back as 3.4 million years ago. Although simple, this pioneer technology was effective enough to last for nearly 1 million years, being used long after the first Homo had arrived on the scene.
Toolmaking opened up a vast new range of possibilities. It enabled hominids to dramatically expand their sources of food. Hitherto, they had depended on fruits, roots, herbs and insects. Now they could use stone flakes to cut up animal carcasses so they could carry the meat to safe locations. Meat and marrow fat provided a nutritious and concentrated food, nourishing brain development. And brain development was the stimulus propelling the evolution of Homo.
CHAPTER 16
PIONEERS
THE THRESHOLD between australopithecines and the first species of Homo is little more than a blur. The fossil record between 2.5 and 2.0 million years ago is so sparse that palaeoanthropologists have yet to determine which species of Homo came first and when it emerged from the ranks of australopithecines. What appears certain is that Homo arrived at a time when the world was experiencing another dramatic change in climate, leading in Africa to a cooler, drier environment in which forests there shrank further and savannah grasslands expanded. Added to the impact of global climate change in eastern Africa was a local bout of extreme climate variability—wild swings from wet to dry conditions followed by droughts—which put enormous pressure on hominids to adapt.
Two species have been named as contenders for the earliest examples of humankind: Homo habilis and Homo rudolfensis. But strong doubts remain about the credentials of both of them. Homo habilis—handy man—is the name given in 1964 to a collection of fossils found by the Leakeys at Olduvai Gorge to describe what was said at the time to be the world’s oldest toolmaker, dating back 1.8 million years. Although the brain size of habilis (600–700 cubic centimetres) was below the level previously agreed to constitute qualification for a listing as human (at least 750 cubic centimetres), the Leakeys argued that because of its dexterity in making tools, it merited inclusion. Similar fossils subsequently recovered from other sites in eastern and southern Africa, ranging in age from 2.3 to 1.6 million years ago, have been placed in the same category.
One difficulty with Homo habilis is that it differs little from contemporary australopithecines: It is similar in size to them—about half the height of a modern human; and its brain capacity is generally only slightly larger. Moreover, it includes a disparate variety of fossils: Some faces are small and projecting, and others are large and flat; lower jaws also vary in size and shape.
Because of the variation, many palaeoanthropologists prefer to place the larger specimens of habilis in a separate category: Homo rudolfensis. The key exhibit is the 1470 skull found by Bernard Ngeneo at Koobi Fora in 1972 and named Homo rudolfensis in 1986 to commemorate its location—Lake Rudolf, the previous name for Lake Turkana. Dated as 1.9 million years old, it has a long and broad face with eyes set well apart and a single continuous brow ridge. Its braincase is relatively large, with a volume of 750 cubic centimetres. The drawback about Homo rudolfensis is that there