Cooking, Fire and Human Evolution

Evolution — POSTED BY Joe Mellen on July 26, 2010 at 2:14 pm

Did Learning to Cook Push Our Ancestors Toward Modernity?

Intriguing evidence shows that cooking may have been the spark that set human evolution blazing toward higher intelligence and civilization.

It has long been a fascinating puzzle to scientists: Why did our apelike ancestors come down from the trees and develop brains many times larger than they actually needed? Many theories have been discussed, most of which revolve around social cooperation; big brains would have helped our ancestors develop language, make better tools, plan hunting strategies, and pass on complex culture to the next generation.

From Suite 101 by Jenny Ashford

However, some scientists have pointed out that other animals — chimpanzees and crows, for example — are also able to make and use tools, can communicate adequately to suit their purposes, and live within a matrix of socially intricate relationships. Yet these animals do not possess the enormous brains that humans do, relative to their body size. Therefore some other factor must have led to our runaway brain growth, and in his 2009 book Catching Fire, biological anthropologist Richard Wrangham makes a case for cooking.

The Quest for Fire

It is not currently known when early hominids began controlling fire. Estimates range from half a million years ago to as recently as the Upper Paleolithic, though a large consensus has advocated for a date about 200,000 years ago, just as the modern Homo sapiens was beginning to emerge. The first discovery of fire was likely accidental, but possible archeological evidence of controlled fires made by our progenitors as well as by Neandertals begin to appear as early as 400,000 years ago.

While it is unclear whether these early fires were used to cook food, Wrangham argues that even if no cooking was yet taking place, the mere act of keeping a fire at a campsite would have had enormous consequences. Fire would have kept predators at bay, allowing our vulnerable ancestors to sleep on the ground, rather than in trees as other apes do. This ground living could explain some of the anatomical changes early hominids eventually underwent, such as the loss of climbing efficiency, and the lengthening of the legs and flattening of the feet, which facilitated upright walking.

From Australopithecus to Homo Erectus

One of the greatest questions in human evolution remains: What caused the large and relatively rapid leap from the apelike australopithecines to the more modern Homo erectus and on to H. sapiens? Richard Wrangham and others think the major cause might have been using fire to cook food, pointing out that many of the physical differences between the species point to this conclusion.

Firstly, the teeth of Homo became smaller and duller than those of australopithecines, as would be expected if the former had grown accustomed to softer, cooked foods. In addition, the jaw muscles of Homo are far smaller and weaker than those of our apelike ancestors, whose jaw muscles extended all the way to the top of the skull. Finally, the ribs of Homo are far less flared, suggesting the smaller gut of a creature who ate food that digested easily; apes (including australopithecines) have large digestive systems to accommodate their hard, fibrous diets.

Cooking, Calories and Big Brains

Perhaps the most compelling evidence for the cooking hypothesis lies in our enormous brains. Brains are extremely costly organs to operate, and most other species on the planet get by just fine with far less brain power than humans employ, suggesting that extra brain tissue is too expensive a luxury, and generally not worth the energy needed to run it. But eating cooked food — which is something wild animals rarely, if ever, do — has a distinct advantage. Cooking not only makes food easier to chew and digest, it also allows more energy to be released for use in the body.

Several studies have borne this out. For example, a 1990 Belgian study showed that cooked eggs released 91-94% of their protein to be used as fuel by humans, whereas raw eggs released only 51-65%. Conversely, a German study on the effect of a raw food diet on humans found that a third of the subjects, despite eating enough calories, became dangerously underweight and energy deficient, and half the studied women experienced amenorrhea due to insufficient BMI. Cooking food seems to power up its caloric punch, though the reason for this is still unclear. In the modern West, this is a recipe for chronic obesity, but in the early days of hominid evolution, anything that increased the energy value of food would have been a tremendous boon, allowing us to feed our bodies and have calories left over to fuel the growth of our gigantic brains.

Cooking as the Basis for Civilization

Richard Wrangham further theorizes that control of fire and cooking may have been the basis of modern civilization. A dependence on foraged food and hunted meat that was prepared and cooked primarily by women might have been the catalyst for pair bonding and small family units. Additionally, sitting around a fire for safety and to share food might have rewarded cooperation and tolerance, making larger societies possible.