Catching Fire: How Cooking Made Us Human by Richard Wrangham Page B

hundred thousand years ago. The transition was too recent to correspond to the origin of cooking, however, because Homo heidelbergensis was already using fire at Beeches Pit, Schöningen, and elsewhere four hundred thousand years ago. Nor does the transition to Homo sapiens show the kinds of change we are looking for. Homo heidelbergensis was merely a more robust form of human than Homo sapiens , with a large face, less rounded head, and slightly smaller brain. Most of the differences between these two species are too small and not obviously related to diet. We can be confident that cooking began more than three hundred thousand years ago, before Homo sapiens emerged.

    Homo heidelbergensis evolved from Homo erectus in Africa from eight to six hundred thousand years ago. The timing of the erectus-heidelbergensis transition provides a reasonably comfortable fit with the archaeological data on the control of fire becoming particularly scarce. The main changes in anatomy from Homo erectus to Homo heidelbergensis were an increase in cranial capacity (brain volume) of around 30 percent, a higher forehead, and a flatter face. These are smaller modifications than the differences between a chimpanzee and a gorilla, and the modifications show little correspondence to changes in the diet. So this Pleistocene transition does not look favorable. It is a possibility for when cooking began, but not a promising one.

    The only other option is the original change, from habilines to Homo erectus . This shift happened between 1.9 million and 1.8 million years ago and involved much larger changes in anatomy than any subsequent transitions. Recall that in many ways habilines were apelike. Like the australopithecines, they appear to have had two effective styles of locomotion. They walked upright and can be reconstructed as having had sufficiently strong and mobile arms to be good climbers. Their small size must have helped them in trees. They are estimated to have stood about 1 to 1.3 meters tall (3 feet 3 inches to 4 feet 3 inches) and appear to have weighed about the same as a chimpanzee, around thirty-two kilograms (seventy pounds) for a female and thirty-seven kilograms (eighty-one pounds) for a male. Despite their small bodies, they had much bigger chewing teeth than in any subsequent species of the genus Homo : the surface areas of three representative chewing teeth decreased by 21 percent from habilines to early Homo erectus . Habilines’ larger teeth imply a bulky diet that required a lot of chewing.

    Homo erectus did not exhibit the apelike features of the habilines. In the evolution of Homo erectus from habilines, we find the largest reduction in tooth size in the last six million years of human evolution, the largest increase in body size, and a disappearance of the shoulder, arm, and trunk adaptations that apparently enabled habilines to climb well. Additionally, Homo erectus had a less flared rib cage and a narrower pelvis than the australopithecines, both features indicating that they had a smaller gut. There was a 42 percent increase in cranial capacity. Homo erectus was also the first species in our lineage to extend its range beyond Africa: it was recorded in western Asia by 1.7 million years ago, Indonesia in Southeast Asia by 1.6 million years ago, and Spain by 1.4 million years ago. The reduction in tooth size, the signs of increased energy availability in larger brains and bodies, the indication of smaller guts, and the ability to exploit new kinds of habitat all support the idea that cooking was responsible for the evolution of Homo erectus.

    Even the reduction in climbing ability fits the hypothesis that Homo erectus cooked. Homo erectus presumably climbed no better than modern humans do, unlike the agile habilines. This shift suggests that Homo erectus slept on the ground, a novel behavior that would have depended on their controlling fire to provide light to see predators and scare them away. Primates hardly ever sleep