Cooking may have driven human evolution nearly 2 million years ago

Modern humans spend significantly less time feeding than non-human primates. You spend an average of 5% of your waking hours consuming food, while your typical chimpanzee spends upwards of 33%. And it's all because of cooking. Now, newly published research suggests that our ancestors' abilities to whip up a hot meal may have played crucial role in driving our evolutionary development.

In a paper published in the latest issue of Proceedings of the National Academy of Sciences, evolutionary biologists at Harvard University attribute this enormous discrepancy in feeding habits to "a substantial evolutionary rate change in feeding time...along the human branch after the human-chimpanzee split."

In other words, at some point after their evolutionary divergence from apes, members of the genus Homo cut back significantly on their time spent eating. This conclusion seems straightforward enough — but what could account for such a dramatic difference in feeding time between humans and primates?

According to the researchers, the answer lies in the uniquely human activity of consuming cooked food, which not only provided our evolutionary ancestors the benefit of increased caloric intake, but presumably a shorter feeding time. Chris Organ, one of the researchers involved in the study, estimates that in the absence of cooking, the state of our teeth as they exist today would require us to spend almost half our days eating.

However the time and manner in which cooking came into practice is uncertain. While some of the most compelling evidence for humanity's mastery of fire dates to just 800,000 years ago, many of our evolutionary ancestors — like H. erectus, who lived close to 2 million years ago — are believed to have spent as little time eating as we do today. Given that, how could H. erectus have managed to cut down on its feeding time without having fire with which to cook? Could our ancestors' use of fire really predate existing evidence by over a million years?

In an effort to shed some light on the history of humanity's relationship with cooking, the researchers traced their way chronologically through 14 specimens spanning five species of the genus Homo, beginning with H. habilis (~ 2.3 million years ago) and ending with modern H. sapiens.

What they found in the specimens was surprising. What they observed was an initially steady decline in molar size — consistent with a gradual reduction in overall body mass — followed by a dramatic decrease in molar size that the researchers claim occurred too rapidly to have been driven by the rate of head, jaw, and body-size evolution alone.

While the oldest members of the genus, H. habilis and H. rudolfensis demonstrated a gradual reduction in molar size, the three most recent species of humans — H. erectus, H. neanderthalensis, and H. sapiens — appeared to have evolved small molars relatively quickly.

The scientists concluded that the advent of cooking, spurred by an early mastery of fire, could therefore explain not only a dramatic decrease in eating-time, but a rapid reduction of human tooth size, as well — meaning that over 1.9 million years ago, the world's very first chef may have inadvertently accelerated the course of human evolution by obviating our need for big teeth. As Organ puts it, the research team's findings are "part of an emerging body of science that shows cooking itself is important for our biology; that is, we are biologically adapted for cooking food."

Via Proceedings of the National Academy of Sciences
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