Introduction - Making the Case for Cooking
Despite the fact that there is not a single human society that has ever subsisted on an all-raw food diet (based on either animal or vegetable foods) the idea that raw is "natural" persists. While such a diet may be possible in the context of our modern food system, the practicality and survivability of "raw" in our ancestral environment (where food scarcity and a high energetic expenditure was required to forage and hunt) is questionable. Looking at the Wikipedia.com entry for "Raw Veganism" one can see how even in the days of supermarkets and abundant food, the definition of "raw" is still stretched considerably:
"Raw veganism is a diet that combines the concepts of veganism and raw foodism. It excludes all food of animal origin, as well as food cooked at a temperature above 48 degrees Celsius (118 degrees Fahrenheit). A raw vegan diet includes raw vegetables and fruits, nuts and nut pastes, grain and legume sprouts, seeds, plant oils, sea vegetables, herbs, and fresh juices." (emphasis mine)
In such a diet the majority of calories may come from foods that are considered "raw", but are nonetheless processed by modern technology. It is unlikely that our prehistoric ancestors would have had the stone-age equivalent of blenders for making nut butters, presses for extracting vegetable oils, and low-heat ovens and dehydrators for "heating" (don't say cooking!) their food.
Another inconvenient fact is that "raw" dietary staples such as sprouted grains and legumes were unavailable during the vast Pleistocene epoch from which modern humans arose. Domesticated cereal grasses and legumes only appeared 10,000 years ago with the dawn of the agricultural revolution, making their regular consumption prior to that point sporadic, and seasonal, at best.
What then, is the alternative?
It is my belief that cooked food, particularly starchy tubers and animal flesh, is what dominated the ancestral human dietary. In the following sections, I will set out to back up this statement by:
- Drawing the connection between "form" and "function" (namely, that our anatomy reflects evolutionary pressures and can therefore be used to identify what those pressures were).
- Presenting evidence that suggests that the great apes are our closest living relatives, and as such, they provide the best examples for us to begin our anatomical comparison.
- Describing what is known about great ape anatomy and how it differs from that of modern humans.
- Looking to early hominid fossil evidence to see what we can infer about the evolutionary steps and that resulted in our current form.
- Presenting a practical summary of the implications surrounding an ancestral diet of cooked foods.
Part 1 - Form Follows Function
"It is the pervading law of all things organic and inorganic, of all things physical and metaphysical, of all things human and all things superhuman, of all true manifestations of the head, of the heart, of the soul, that the life is recognizable in its expression, that form forever follows function. This is the law."
- Louis Sullivan, "The Tall Office Building Artistically Considered"
In his 1896 essay on the design of the then novel "office building", Louis Sullivan rightly observed that, in the natural world, forms such as the wings of birds, human hands, or the fins of fishes, are a product of the function they perform. This function may be readily apparent; a lion's claws are curved and sharp so that it may better grasp prey, or more obscure, a moth's tongue may be a particular length so that it can feed on a specific type of orchid, but the underlying truth to this premise remains.
Since the genesis of the first living cell, evolution has been a matter of exploiting new resources or exploiting resources better than someone or something else. Biological forms are therefore a reflection of this drive and while sexual selection and random mutation do play a role, they do so only to the extent that they do not disturb this general trend towards more efficient utilization of available resources.
For example, if we look a giraffe, we can see that its most striking feature is an extremely long neck. It is unlikely that the giraffe possessed such a neck for purposes solely related to mating or a random mutation. It is presumable, however, that an extended neck, one that places significant demands on the animal's physiology, also conferred a significant enough benefit to outweigh the cost to grow it and any disadvantages that may have resulted. The suggested benefit would likely be greater access to food resources unavailable to competitors. There are other adaptations that support this theory as well, like the lengthy giraffe tongue, which extends its reach by nearly a foot. (For an interesting theory regarding the coevolution of giraffes and certain acacia trees, check out "Winning by a Neck".)
However, fully exploring the development of the giraffe's neck, and the evolutionary pressures that may have spurned it's exceptional length, is limited by a lack of intermediate forms in the fossil record as well as a dearth of close living relatives (excepting for the Okapi.) This is not the case with humans as we have several close living relatives and an abundance of ancestral intermediates that we can investigate.
Part 2 - Well I'll Be a Great Ape's Cousin
The Great Apes, Source: L. Brent Vaughan, Hill's Practical Reference Library of General Knowledge (New York: Dixon, Hanson & Company, 1906)
Human (noun) - A bipedal primate mammal (Homo sapiens) : man; broadly : hominid
- Merriam-Webster Dictionary
While the work of Charles Darwin (author of the paradigm shifting "On The Origin of Species") and Gregor Mendel (The "father" of modern genetics) set the stage for our contemporary understanding of the process of evolution, it was the discovery of DNA and RNA (presented in 1953 by Watson and Crick) that provided us with the clearest look yet at evolution's secrets.
Comparing the degree of similarity between species allows us to infer their relative evolutionary closeness and relation. At present, the most reliable metric we have available for assessing the relatedness of species (and by inference how much time has passed since the two species were in fact one species) is gene sequencing. While we can plainly see that humans are more closely related to apes than birds, analyzing simple morphological similarities (i.e. physical traits) can only take us so far. However, even with molecular evidence, drawing absolute conclusions about evolutionary relationships is difficult.
It is still uncertain whether humans are more closely related to chimpanzees, gorillas, or even orangutans. In 2005 scientists completed the genetic sequencing of chimpanzee DNA and it was thus concluded that they are our closest relatives, sharing a full 96% of our genetic material. (By comparison, we have an 88% overlap with rodents and 60% with chickens.) Since then, it has been argued that Orangutans (based on the work of Anthropology professor Jeffrey H. Schwartz) and gorillas are more closely related to humans (based on the recent completion of gorilla DNA sequencing.)
Fortunately, for our purposes, the question of which great ape is our closest cousin is less important than the fact that we are closely related to all of the great apes. This point is well summed up by Frans de Waal, who, made the following statement in a National Geographic News article:
"Darwin wasn't just provocative in saying that we descend from the apes—he didn't go far enough. We are apes in every way, from our long arms and tailless bodies to our habits and temperament."
As philosopher David Hume said in his 1772 essay An Enquiry Concering Human Understanding, "From causes which appear similar we expect similar effects." In other words, we would expect that were humans adapted to diets and lifestyles similar to that of their great ape cousins, they would look and act more like them. As this is clearly not the case, we will need to explore these "causes" and "effects" more thoroughly.
Part 3 - Monkey See Human Eat?
|Human, Chimpanzee and Orangutan Digestive Tracts. Image Source: CNSweb.org|
"Among the great apes (the gorilla,the orangutan,the bonobo, and the chimpanzee) and ourselves, only humans and chimpanzees hunt and eat meat on a frequent basis. Since neither humans or chimpanzees are truly carnivorous - most traditional human societies eat a diet made up mostly of plant foods - we are considered omnivores. The important decisions about what to eat and when to eat it should therefore be based on the nutritional costs and benefits of obtaining that food compared to the essential nutrients that the food provides."
-Dr. Craig B. Stanford, "The Predatory Behavior and Ecology of Wild Chimpanzees"
Despite our genetic similarities, humans differ from the great apes in numerous ways. The raw food diet of our cousins is made possible by adaptations that we lack. The first of these adaptations would be the large mouths, powerful lips, and strong muscles possessed by great apes who spend a significant portion of their day simply chewing a diet largely comprised of fruits, seeds, nuts, leaves, shoots, and twigs supplemented by relatively small amount of hunted animal flesh (that of chimpanzees) and green foliage (gorillas).
Highly developed facial muscles (connected to both the jaw and the lips) along with a pronounced skeletal scaffolding in the form of cranial ridges allow great apes to accomplish their feats of mastication. When body size is taken into account, it would be expected that a human being eating a such diet would also spend much of his or her day feeding (48% to be exact) and thus similar adaptations for prolonged bouts of chewing would be expected.
Moving down from the head, we come upon the issue of digestive machinery. In orangutans and gorillas, large cecums (colon) and rich populations of microbes allow fermentative digestion to occur. Fermentation of plant cellulose in the cecum provides usable short chain fatty acids from the otherwise indigestible plant fiber. In a study called "The western lowland gorilla diet has implications for the health of humans and other hominoids", researchers discovered that nearly 60% of the gorilla's metabolizable energy comes from "short-chain fatty acids (SCFA) derived from colonic fermentation of fiber." Although the same researchers proposed that "humans also evolved consuming similar high foliage, high fiber diets", they do not suggest a mechanism by which this would be possible.
Lacking the fermentative abilities of gorillas and orangs, both chimps and humans have had to turn to food resources other than just green plants and the occasional bug. For chimps, this means a social structure of mobile bands that follow the fruiting of various plant species. While chimps do hunt, only 2% of the chimpanzee diet is made up of hunted foods, with the remaining 95% derived from low-energy plant parts such as fruits, flowers, and leaves. It is between bouts of plant feeding (while they are digesting in fact) that chimps will hunt and eat meat. African folklore also suggests that chimpanzees may even forgo fresh meat for the maggots that grow on a hunted carcass.
Returning to the head, there is another problem with the assumption that the diet of other great apes is suitable for humans. In evolution, there is no such thing as a "free" organ, and brains are especially expensive to feed. They require a constant supply of glucose, without which, they die, causing all sort of problems for the organism in question. In the table below, you can see what the "expected" ration of organs and other body tissues would be for an average primate of our size.
|From: Brains and guts in human evolution: The Expensive Tissue Hypothesis|
As you can see, while the heart, kidneys, and liver are the size that would be expected, our brains are much larger and our guts are much smaller. This energetic trade-off (large brains for small guts) indicates that human evolution diverged from that of our ape cousins by way of a significant change in our diets. This change would have simultaneously lessened the demand for a robust digestive apparatus capable of processing large amounts of plant foods while also providing enough energy to feed our growing brain. The "Man the Hunter" hypothesis is typically cited as the reason for this shift, but can an increase in animal foods alone explain the dramatic differences observed between modern humans and apes?
Part 4 - Digging for Bones
|Ape and Human Mandible Shapes, Source: Evolution Archive - Upper Paleolithic|
"The newly delicious cooked diet led to their evolving smaller guts, bigger bodies, and reduced body hair; more running; more hunting; longer lives; calmer temperaments; and a new emphasis on bonding between females and males. The softness of their cooked plant foods selected for smaller teeth, the protection fire provided at night enabled them to sleep on the ground and lose their climbing ability, and females likely began cooking for males, whose time was increasingly free to search for more meat and honey. While other habilines elsewhere in Africa continued for several hundred thousand years to eat their food raw, one lucky group became Homo erectus - and humanity began."
-Richard Wrangham, "Catching Fire - How Cooking Made Us Human" pg. 194
The first pre-human ancestor recognized as distinct from the other ancestral ape lineages was the Australopithecus. The "walking ape" appearing in Africa around 3.5 million years ago. However, structural adaptations to the hands and shoulder blade similar to that of modern arboreal apes suggest that Australopithecus was still an adept climber. This suggested that it may have continued to sleep in trees in much of the same way as modern chimpanzees and young gorillas (mature gorillas are large enough to sleep on the ground without having to be overly concerned about attacks from predators).
The Australopiths also had smaller brains (small relative to that of modern humans but still more developed than that of modern apes), flaring rib cages, and flared pelvises of modern great apes, which suggests similarly large digestive tracts and a raw plant-based dietary. Increased exploitation of starchy tubers may explain the benefit conferred by walking (more efficient in marginal woodland environments in addition to allowing food to be carried in the hands) as well as the progressively larger teeth seen in the Australopithecine line.
The second significant step towards modern humans came with the dawn of Homo habilis approximately 2.3 to 1.4 million years ago. With refined hand bones, H. habilis had the dexterity to make and use stone tools, presumably for scavenging meat and marrow. He was not yet a formidable creature (there is ample evidence suggesting that H. habilis was a favored meal for sabre-toothed cats like Dinofelis) but the increased caloric value of meat (versus plant foods) can sufficiently explain the increased size of the habiline brain compared to that of australopithecus. But, if meat eating can explain the transition between australopith to habiline, it does not explain the tremendous increase in brain size, the loss of climbing adaptations, and further decreases in tooth size seen in the next step towards modern man.
Appearing around 1.8 million years ago, Homo erectus (the general designation for both the Asian H. Erectus and African H. Ergaster which were contemporaries of each other and either of which may have been the direct ancestor to modern humans) is the first human ancestor who may have had controlled use of fire (possibly "harvested" first from wild fires, and later struck from natural sources of flint) as well as a "hunter gatherer" social structure.
On one hand, use of fire would have made sleeping on the ground safe as all animals (excepting for humans) have an instinctual fear of fire. It would have also provided warmth and allowed for an expansion into less temperate climates. The emergence of hunter-gatherer social groups was also made possible by using fire to cook food as the commitment to a day of hunting would be impossible if a day's worth of calories could not be consumed after returning to camp at night. As with modern hunter-gatherers, cooking also allows for gathering to provide for a baseline level of food resources as hunting expeditions are often unsuccessful.
Homo Erectus would have also enjoyed increased access to food resources conferred by cooking. Specifically, reproductive and survival benefits would have been derived from increased food quality (decreased energetic cost for digestion by as much as 5-15% and increased surface area for the action of digestive enzymes) and decreased exposure to food toxins and microorganisms destroyed by fire.
Part 5 - Dinner Time!
"A man becomes a cook: but he is born a roaster of flesh."
-Jean Anthelme Brillat-Savarin "The Physiology of Taste"
So, what does an ancestral diet based on cooked foods mean for modern humans? For one, it helps explain our penchant for nicely seared steaks, golden brown crusts, and fried foods. All of which owe their particular appeal to Maillard compounds formed during the cooking process. In the same way that fat and sugar sing to us an evolutionary siren song about caloric potential, Maillard compounds inform our senses of caloric availability.
Second, it indicates that foods best suited for cooking, gathered starchy roots and tubers as well as hunted animals likely formed the centerpiece of the ancestral diet. But, the proportion of starch to flesh is seems largely irrelevant. This point is illustrated by Katharine Milton in "Hunter-gatherer diets—a different perspective":
"Data on modern-day hunter-gatherers as well as hunter-gatherer-agriculturalists who consumed traditional diets indicate that such societies are largely free of diseases of civilization regardless of whether a high percentage of dietary energy is supplied by wild animal foods (eg, in Canadian Eskimos), wild plant foods (eg, in the !Kung), or domesticated plant foods taken primarily from a single cultivar (eg, in the Yanomamo)."
Third, it reveals a path to weigh management that doesn't involve counting calories. While a raw vegan diet is not one that I would recommend, increasing the proportion of raw foods in ones diet relative to cooked foods (ideally also well sourced and nutritionally sound) would predictably decrease the amount of usable calories thus facilitating weight loss efforts.
Finally, it tells us that the ritual of the community or family meal, is primary to our well being. If our ancestral lineage progressed like that of the chimpanzee, we would eat in solitude but that is not the case for us. In fact, numerous studies have supported this notion by showing that a shared family meal can lead to better overall communication, adjustment, and nutrition.
Conclusion - Man the Cook
In the midst of a nutritional environment that is dominated by highly processed food products (to call them simply "food" would be unwise) it is understandable that many people initially react by moving too far in the opposite direction. Over the course of my own journey, I too have been tempted by the obvious appeal of naturalism, to the notion that what is good and right is the untouched and unspoiled products of mother earth. But, this is a romantic notion that does not reflect the likely truth of our origins. Rather than rejecting cooking, we would do well to embrace it. Let your cooking be an act of communion with your ancestors, with the earth, and with the animals and plants that are sacrificed in the preparation of your food.
In short, cook well, eat well, and be well.
For further reading, I suggest Richard Wrangham's "Catching Fire - How Cooking Made us Human"
Also, you can watch the BBC Documentary "Did Cooking Make Us Human?" in the window below.