Why We Heat Our Food: The Evolutionary Significance of Cooking
The last time you fried an egg or made some rice, you probably didn’t think much about why you were cooking. Sure, you could say because you were hungry, or because you were cooking a meal with your family. But you might wonder, why do humans cook at all? Is there a reason that we cook our steak, but chimpanzees (or any other species for that matter) don’t? In this article, we’ll explore the evolutionary significance of cooking, thanks to research by Harvard scientists Rachel Carmody and Richard Wrangham.
Carmody and Wrangham suggest that a main reason early humans turned to cooking food with fire is that doing so causes a rise in the net energy value of the food. This provided a survival and reproductive advantage allowing members of the homo genus to outcompete their competitors. The evidence for cooked food’s increase in overall energy falls into two categories: (1) the effect of cooking plant foods and (2) the effect of cooking meat.
Beneficial effects of cooking plant foods:
Increased BMI and improved physical performance
In a study done of modern urban-dwelling “raw foodists” (those that choose to eat the majority of their food vegetarian and uncooked like raw vegetables), it was determined that on average they had much lower body mass indexes (BMIs), an indicator of being underweight and prone to related illnesses (such as amenorrhea, a condition causing menstrual irregularities and decreased reproductive success). This was determined not to be related to the fact that they were vegetarian, as vegetarians eating a typical cooked diet had normal BMI ranges; in this case the reduced BMI of the raw foodists was simply a result of not cooking their food.
Increased digestibility of starch
Applying heat to a starch allows for the collapse of its crystal-like granule structure in a process called gelatinization. This makes it easier to convert starch to sugars and dextrins for the body to use. Carmody and Wrangham’s compilation of various studies determined that the increase in energy related to the improved digestibility of cooked starches varies from 12.1% more energy from oats to 35% from green bananas. This is significant evolutionarily because this allowed individuals to obtain more usable energy from a food simply by heating it.
Beneficial effects of cooking meat:
Increased food intake
It is easy to observe that cooking meat improves its taste, and the better something tastes, the more of it you want to eat. Carmody and Wrangham found evidence that cooking changes meat flavor and texture in ways that improve palatability, and therefore intake; and the more food our ancestors were able to eat, the more energy they had for going about their lives.
Cooking meat should have positive impacts on its digestibility due to the fact that heat-induced denaturation of protein makes the protein more easily broken down by the body. However, no direct evidence has yet been found to prove this is the case for meat and further research is needed.
Lower costs of immune response costs
Foodborne bacteria in uncooked meat result in upregulation of the human immune system (which is why you get a fever when you are sick). This has significant energetic costs. Carmody and Wrangham determined that if you were to eat only raw meat, you would spend 6.9 years of your life fighting off infection with elevated immune activation. In contrast, cooking allows your body to expend less than a day’s worth of metabolism towards increasing your immune system’s response.
For all of these reasons, it is clear that cooking food provided energetic advantages to early humans, allowing for more energy to be spent in hunting, survival, and reproduction, and giving us the advantage to dominate and ultimately become a species numbering over 7.5 billion globally. So the next time you’re roasting chicken or cooking some lentils, thank our early ancestors for figuring out how.
Last Updated: October 28th, 2022
Carmody, R. N., et al. “Energetic Consequences of Thermal and Nonthermal Food Processing.” Proceedings of the National Academy of Sciences, vol. 108, no. 48, Nov. 2011, pp. 19199–203. DOI.org (Crossref), doi:10.1073/pnas.1112128108.
Carmody, Rachel N., and Richard W. Wrangham. “The Energetic Significance of Cooking.” Journal of Human Evolution, vol. 57, no. 4, Oct. 2009, pp. 379–91. DOI.org (Crossref), doi:10.1016/j.jhevol.2009.02.011.