Chimpanzees spend a remarkable amount of their day chewing food. Some chimpanzees spend half of their day on feeding. Modern humans spend only around five percent of the day on eating. Wrangham believes the ability of humans to cook food is what separates us from other animals. It is not that chimpanzees and other primates eat much more food than we do, but it is the types of food like raw meat and other unprocessed foods that need to be chewed extensively to extract nutrients and calories. There is evidence to suggest that hominids were eating raw meat at least three million years ago. Antelope bones have been found with tool marks on them, suggesting the use of tools by humans to butcher antelope meat and and extracting marrow from the bone. Daniel Lieberman, an evolutionary anthropologist at Harvard University, believes that before learning how to cook, hominids used stone tools to slice raw meat and smash root vegetables, making it easier to chew and digest. This would have cut down on the amount of feeding time of hominids well before the advent of cooking. There are many ways to cook food without fire, but fire would have been the most likely energy source our hominid ancestors used to cook food. Concrete evidence of fire use only goes back to around 400,000 years ago, but a report by Harvard researchers analyzed tooth sizes across hominid species, and deduced that Homo erectus, Neanderthals, and modern humans developed small molars quite rapidly, which they were not able to match with increasing head and jaw sizes. This led them to the conclusion that some other factor caused these molars to shrink in size. They believe the advent of cooking food made it easier to chew various foods like meat and tubers that were common in the diets of hominids at the time. Over time, these hominids evolved to have smaller teeth and not the larger teeth of earlier hominids that were required to chew uncooked meat and other difficult to chew foods like tubers.
Cooking food goes beyond just making food easier to chew. Potentially harmful bacteria are killed in the process of heating and cooking food. This would have been especially important in cooking meat from wild boars and fowls. Cooked foods also unlock almost all of their nutrients for absorption, where raw foods only yield around 30-40 percent of their nutrients. It’s difficult to say what the palettes of our hominid ancestors were like, but judging from our current tastes, cooked food generally tastes better than raw foods. Feeding time would not only have been shorter, but also more enjoyable. Less feeding time meant more time to accomplish other things. Extra time to look for more food sources and figuring out new more effective ways to avoid predators would have been greatly beneficial to the fitness of early hominids and our own human ancestors. Being able to consume more calories also meant we were able to nourish larger brains. Human brains are much larger, relative to body size, than other hominids and primates. Our brains require around 20 percent of the total energy our bodies use. It would have been impossible to evolve and sustain a large brain without figuring out a way to extract as much nutrients from food as possible, without spending half the day chewing food.
Humans are certainly a unique species and there are a number of different explanations to differentiate us from other animals. We can talk about our complex brains that give us the intellectual ability to create and build computers and cars, but this wouldn’t be possible if we couldn’t nourish our large brains by consuming food and extracting nutrients as efficiently as possible. Figuring out how to cook food to make them more palatable and easily digestible may be the defining feature that separates humans from other animal species.