The story of the evolution of humans is a long one, one that spans over millions of years. By that logic, the evolution of the human diet is just as long and arduous.
How much, exactly, has the human diet evolved? And what were the factors that lead to each evolutionary step? Did our diets allow us to evolve more or did our evolution lead to changes in our diets?
While it all seems a bit like a “which came first the chicken or egg?” type of story, significant amounts of research done over many years has given scientist insight into where our diets started and how it affects us today.
Anthropologists like Richard Wrangham, Richard B. Lee, and S. Boyd Eaton have put in their time researching all of this and have all come up with their own findings on on prehistoric diets. But in order to truly understand where we came from we need to start from the beginning, well before we were homo sapiens traversing the savannah. We need to go back 4.4 million years, to the dawn of man kind.
4.4 Million- 2 million years ago and The Emergence of the Genus Homo
2.4 million years is a very large range of time and, as one might expect, during this time as the ancestors to modern day humans evolved, so too did their diets. Mark F. Teaford and Peter S. Ungar researched the characteristics of the teeth and skulls of early australopithecines, your ancestors that came after the chimps, and found that during that span of time the diets of all of these ancestors to homo sapiens changed dramatically (Teaford & Ungar, 2000).
Their research showed that over this 2.4 -million-year time period the predecessors to the genus homo, the ancestor right before homo sapiens, made an appearance, they went from eating leafs and seeds and berries, like their chimp ancestors, to adding things like insects to their diets.
Then about 2 million years ago something big happened, something huge caused the emergence of the genus Homo, the first step towards Homo Sapiens. So what caused this change?
In 1966 fifty anthropologists who studied traditional foraging people came together and developed the theory “Man the Hunter” (Stanford, 1999). Their theory said that hunting required a significant amount of intelligence and communication, therefore requiring more brain mass to be intelligent enough to track and hunt prey.
The change from mostly foraging to being able to track and hunt prey created a significant dietary change allowing hominids to eat more meat. The addition of more meat to the diet provided the extra calories and protein needed to make a larger brain function. But evidence shows that while the need for more fuel for bigger brains did lead to hunting, there is something more, something else caused the jump from Homo erectus to Homo sapiens.
Fire, the Next Stepping Stone
One key thing that needs to be noted it that while hunting provided a decent amount of protein to the diets of the society, hunting trips only happened a few times a year. The main food source for many hunter-gather societies was, and still is today, actually provided by the gathering portion of the term hunter-gatherer.
Anthropologist Richard B. Lee spent many years of his life living with and studying the !Kung Bushmen, a modern day hunter-gather society, of the South African Kalahari Desert in the 1960’s. During his time with the !Kung he found that food provided by gathering actually accounts for “60-80 per cent of the total diet by weight” (Lee, 1968, p. 33).
This would mean that though hunting did change the diets of the early Homo’s it wasn’t significant enough to cause the preceding jumps from homo erectus to homo sapiens. Anthropologists Richard Wrangham disputes the “Man the Hunter” theory in his book Catching Fire: How Cooking Made Us Human. Wrangham says there is one essential piece to early Homo diets that would have pushed the jump from Homo Erectus to Homo heidelbergensis (800,000 years ago) and eventually Homo Sapiens (200,000 years ago). Wrangham suggests that “the transformative moment that gave rise to the genus Homo…stemmed from the control of fire and the advent of cooked meals” (Wrangham, 2009).
Theories on when the genus homo initially was able to control fire range from 40,000 years ago to 1.6 million years ago, 200,000 years after the emergence of Homo erectus. Some of the oldest sites that show evidence for habitual use of fire are Benot Ya’aqov in Israel and Koobi Fora in Kenya.
The site of Benot Ya’aqov is dated to about 790,000 years ago. At the site there is evidence of burnt olive, barley, and grape seeds along with burned flint (Wrangham, 2009). There is also evidence of burnt wood in hearth-like patterns (Wrangham, 2009). These pieces of evidence are enough for anthropologists studying the site to conclude that the early humans that inhabited this site had a significant amount of knowledge on fire making and could make fires at will (Wrangham, 2009).
The second site, Koobi Fora, is considerably older than Benot Ya’aqov, it is dated to about 1.6 million years ago. The evidence here shows controlled fires that were burned with palm wood (Wrangham, 2009). These two sites suggest that both Homo erectus, at Koobi Fora, and Homo heidelbergensis, at Benot Ya’aqov, both had the ability to control fires.
Cooked Foods and Energy Needs
So what exactly does the ability to cook food mean in regards to human evolution? Richard Wrangham devotes a whole chapter of his book Catching Fire: How Cooking Made Us Human to explaining this exact concept. He suggests the control of fire is what led to the ability to cook food and increase the energy acquired from foods as well as shorten the digestive process therefore reducing the energetic costs of digestion.
Wrangham states that “Most important, cooking gelatinizes starch, denatures protein, and softens everything. As a result of these and other processes cooking substantially increases the amount of energy we obtain from our food” (Wrangham, 2009, p. 57). Or put more simply, cooking food makes all of the essential nutrients in foods more readily available to our bodies so that they can digest it more quickly.
One significant hypothesis that adds to the theory of cooked foods effects on human evolution is “The Extensive Tissue Hypothesis.” The human brain uses about 20% of the body’s energy budget everyday even though it only takes up about 2.5% of human body weight. While a chimp brain uses about 13% of its body’s energy and a mammal only 10% at most (Wrangham, 2009). This means that if a human eats 2000 calories in day 400 of those calories are just to fuel its brain, yet for most other mammals it takes half that amount. That is the difference between eating one slice of pizza or two.
This energy expenditure of the brain requires the human body to be able to fuel it properly. In order to do this the genus homo gradually evolved a smaller gut then its ancestors. This suggests that the increased metabolic costs of large human brains are offset by a reduction in other parts of the body needing energy, mainly the gut. This increase in brain size and subsequent reduction in gut size meant that there would need to be an increase in diet quality so that there was enough caloric intake to fund the energy needed to run a human body.
Prehistoric Man: The Super Athlete
Cooking not only would have affected the energy intake for brain function but also general body functioning. Skeletal remains have shown anthropologists that the bodies of early Homo sapiens were equal to that of today’s super athlete.
In his opening lecture for the summer meeting of the Nutrition Society, held in Norwich in 2006, entitled “The ancestral human diet: what was it and should it be a paradigm for contemporary nutrition?” S. Boyd Eaton address this idea and what this means in regards to the dietary intake of prehistoric man. Eaton suggests that they would have needed about 2800 calories a day to properly function.
Wrangham points out that tests done on modern humans have shown that raw food diets are unhealthy and provide less calories then cooked foods. Raw foodist diets have an average caloric intake of 1,460 for women and 1,830 for men (Wrangham, 2009).
This means that there is no way that early Homo sapiens would have been able to function off the raw, uncooked diets of their predecessors. But instead by cooking their foods it made it possible for them to eat stems, soft seed pods and meats, unlike the australopithecines; who would spend a decent amount of their day chewing their foods.
Eaton explains that the super athlete bodies of Homo sapiens also required a diet that provided 35% of their energy from fats, 35% from carbohydrates, and 30% from proteins (Eaton, 2006). In order to get this and still get 2800 calories a day it would require cooking the food. This way they would be able to eat more foods at once because the body could quickly digest everything they ate.
Carbohydrate, Another Key Factor
In recent years’ carbohydrates have gotten a lot of flak from the general public, especially sugars and overly processed foods. While we know that maybe we don’t need to eat some of the over processed foods, there is research showing that carbohydrates are necessary for the human body to function.
In the September 2015 issue of the Quarterly Review of Biology Mark G. Thomas and his colleagues suggest that tubers and starchy plants played an important part in fueling the large brains of ancient Homo sapiens (Zimmer, 2015).
Human saliva contains a very important enzyme called amylase, which breaks down starchy foods. One key factor in the ability of amylase doing its work is one of the biggest factors in the evolution of the human diet: the starch must be cooked.
Dr. Thomas also points out that humans make 18 extra copies, compared to chimpanzees, of the gene that tells our bodies to make the amylase enzyme (Zimmer, 2015). This means that our bodies are more readily made to digest these carb-y starches.
And while Dr. Thomas’ findings, as well as the findings of many of the other researchers discussed here, are just that, findings and not conclusions. There is plenty of information “found” to give us all some pointed insight in to the lives and evolution of the ancestors of our distant past.