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

ago. This would mean that for at least the first 150,000 years after cooking was adopted, human teeth showed no response. Because such a long delay before adapting to a major new influence does not fit the animal pattern, we can conclude that Brace’s idea is wrong. The adaptive changes brought on by the adoption of cooking would surely have been rapid.

    In addition to following quickly, the changes would have been substantial. We can infer this from pairs of species in which lesser differences in diet have large effects. Take chimpanzees and gorillas, two ape species that often share the same forest habitat. In many ways their diets are very similar. Both choose ripe fruits when they are available. Both also supplement their diets with fibrous foods, such as piths and leaves. There is only one important difference in their food choice. When fruits are scarce, gorillas rely on foliage alone, whereas chimpanzees continue to search for fruit every day. Unlike gorillas, chimpanzees never survive only on piths and leaves—presumably because they are physiologically unable to do so.

    The relative ability of these two apes to rely on foliage might at first glance appear to be a trivial matter—especially compared to the introduction of cooking. But many consequences follow from it. To find their vital fruits, chimpanzees must travel farther than gorillas, so they are more agile and smaller. There are differences in distributional range. Unlike chimpanzees, gorillas successfully occupy high-altitude forests without fruits, such as the Virunga Volcanoes of Rwanda, Uganda, and the Democratic Republic of Congo. Chimpanzees are limited to lower altitudes. Like other primates that are able to rely on a leaf diet, gorillas mature earlier, start having babies at a younger age, and reproduce faster.

    Grouping patterns of these species also differ strikingly as a result of the difference in diet. The terrestrial foliage gorillas rely on is easily found and occurs in big patches, allowing their groups to be stable all year. But during food-poor seasons, chimpanzees are driven to travel alone or in small groups as they search for rare fruits. The difference in grouping patterns has further consequences. Gorillas form long-lasting bonds between females and males, whereas chimpanzees do not.

    More than the relatively slight dietary difference that distinguishes gorillas from chimpanzees, cooked food had multiple differences from raw food. Effects of cooking include extra energy, softer food, fireside meals, a safer and more diverse set of food species, and a more predictable food supply during periods of scarcity. Cooking would therefore be expected to increase survival, especially of the vulnerable young. It should also have increased the range of edible foods, allowing extension into new biogeographical zones. The anatomical differences between a cooking and a precooking ancestor should be at least as big as those between a chimpanzee and a gorilla. So whenever cooking was adopted, its effects should be easy to find. We can expect the origin of cooking to be signaled by large, rapid changes in human anatomy appropriate to a softer and more energy-rich diet.

     
     
     
    The search for such changes proves to be rather simple. Before two million years ago, there is no suggestion for the control of fire. Since then there have been only three periods when our ancestors’ evolution was fast and strong enough to justify changes in the species names. They are the times that produced Homo erectus (1.8 million years ago), Homo heidelbergensis (800,000 years ago), and Homo sapiens (200,000 years ago). These are therefore the only times when it is reasonable to infer that cooking could have been adopted.

    Most recent was the evolution of Homo sapiens from an ancestor that is now usually called Homo heidelbergensis. It was a gentle process that began in Africa as early as three hundred thousand years ago and was largely complete by around two