Born in Africa_ The Quest for the Origins of Human Life - Martin Meredith [76]
Hand-axes proved to be a highly successful innovation. They were portable, quick to deploy and adapted to a range of tasks from delicate cutting to hacking through tree branches. The same technology remained in use for more than 1 million years, spreading across Africa and much of western Asia as well as Europe.
Another major achievement of Africa’s ergaster/erectus was to find a way of controlling the use of fire. In 1984, a South African archaeologist, Bob Brain, uncovered 270 fragments of charred animal bone in a cave at Swartkrans, west of Johannesburg, that showed signs of having been heated in a campfire. The bones were found in several distinct layers of limestone, dating between 1.5 and 1.0 million years ago—the earliest direct evidence of the controlled use of fire. Brain concluded that the Swartkrans fire makers had not yet discovered how to start their own fires, but had found ways of keeping alive bushfires commonly started by lightning strikes. Several sites in Kenya have also yielded clues about the early use of fire, dating back to 1.5 million years ago, but the evidence there—in the form of lumps of charred clay—is less conclusive. Other evidence of the controlled use of fire comes from a site at Gesher Benot Ya’aqov in northern Israel, where researchers have found clusters of burnt artefacts—mainly flint implements—dated to about 790,000 years ago at what was probably a Homo erectus camp on the shores of an ancient lake.
The ‘capture’ of fire was a crucial innovation. It enabled early humans to expand their diet by cooking seeds, plant foods and meat. It also provided a source of heat and light and protection from predators. ‘The acquisition of fire’, claims anthropologist Frances Burton, in her study of fire, ‘was the engine that propelled the incredibly fast evolution of humans’.
A Harvard anthropologist, Richard Wrangham, has taken the idea further. He developed the theory that it was the ability of early humans to use fire to produce cooked food that transformed human evolution. Wrangham identifies two crucial steps in the transition from ape to human. The first occurred about 2.5 million years ago when Homo habilis took up meat-eating, thus enhancing brain development. But the second step, according to Wrangham, produced far more dramatic change. It occurred from about 1.9 million years ago when Homo ergaster/erectus emerged on the scene. Wrangham speculates that the reason Homo ergaster/erectus acquired a larger body, a larger brain, smaller teeth, and a smaller stomach and guts was not just because of the meat-eating habit but principally because they had discovered how to cook food. ‘Meat eating has been an important factor in human evolution and nutrition, but it has had less impact on our bodies than cooked food’, he writes in Catching Fire, his book explaining his ‘cooking hypothesis’. Cooking provided early humans with a more nutritious range of food, yielding more energy; less time was needed for digestion; more resources were freed to fuel brain development. It was cooked food that made our brains uniquely large. ‘We humans,’ proclaims Wrangham, ‘are the cooking apes, the creature of the flame’.
Africa’s Homo erectus is also notable for adjusting its anatomy to cope with the growing size of its brain. Whereas the average cranial capacity of Australopithecus afarensis—Lucy’s tribe—had been an estimated 410 cubic centimetres, by the time erectus emerged, its brain had doubled in size to about 900 cubic centimetres, boosted by improved diets that included meat. Giving birth to bigger-brained babies required changes in female anatomy. The shape of Lucy’s birth canal was too narrow to allow for the birth of large-brained babies. For many years, because of a lack of fossil evidence, scientists assumed that the pelvis of a female