Comparative Biochemistry and Physiology Part A 136 (2003) 35–46

Cooking as a biological trait
Richard Wrangham, NancyLou Conklin-Brittain
Department of Anthropology
Harvard University
Peabody Museum
11 Divinity Avenue
Cambridge, MA 02138, USA

    Anthro-apologists are a strange lot.
    They tend to just make bizarre stories up, and then pass these exercises in creative writing off as "science".  They do this by using scientific words, superficially, and frequently incorrectly; this, apparently to impress the naive reader, yet they abandon the logic, scientific method, data, and established findings central to science, itself.  Most of their fanciful writing is transparently absurd; however, in the present case the impressive falsity of the proposed thesis is conveniently presented to us clearly in the title itself, possibly to mercifully save us a lot of time which would be otherwise wasted by reading the entire article.  
     IF cooking were a "biological trait", as claimed, then why do absolutely NO other biological entities or species demonstrate it?  None of the current, not yet fully discovered or counted, 10's of millions of species of Life on this planet, and none of the additional tens of millions of species now extinct, but previously living on this planet, exhibit this "biological trait".  IF cooking were a "biological trait", then why does only the sickest, most self-destructive, most omni-destructive, obese, degenerative disease-creating species: the human, exhibit it?  Clearly, cooking is NOT a "biological trait", as so foolishly claimed, but it is a self-destructive cultural process, practiced only by our own little psychotic-ape species.
    True "biological traits" would be those exhibited by all biological entities, such as: eating, excreting, and reproducing.  Mechanisms of self-repair are also common in "higher" species.

1. Introduction
RW> At least four biologically significant differences are widely recognized between the diets of hunter–gatherers and other great apes.
     At the outset, there is an conveniently-unstated, yet absolutely critical, totally false, and impressively unsupported, perhaps intentionally misleading, assumption that "hunter–gatherers" consume a natural, biologically-correct, diet for our species, and clearly they do not.
     "Hunting" is accomplished with tools, not the equipment inherent to the natural human body, and the cooking of the hunted prey prior to consumption is clearly not a natural process either; it is a fairly recent cultural fad.  Modern epidemiology indicates that the cooking and consumption of animal flesh and animal fats is responsible for the exponentially-growing "degenerative diseases" seen in "technologically-advanced cultures".

RW> First, humans eat more meat than chimpanzees (and other apes)
     So what?  Defenseless, ignorant, and totally helpless human infants are taught to eat "meat" by their ignorant parents, who were taught to do so by their ignorant parents, and so forth -- all the way back to the Neanderthals.  What is the point of mindlessly imitating a Neanderthal lifestyle; haven't we learned something about anatomy, physiology, epidemiology, and nutritional biochemistry since then?  The large amounts of meat and other "animal products" available to "civilized" cultures is merely a result of factory farming, a highly ecologically-destructive process, and very few cultural humans could sustain their level of consumption if they caught, killed, and ate raw their prey.
     Human infants have not been reported to spontaneously kill and consume small animals, e.g. the family cat, due to inherent instincts.  Some chimps, a very small percentage of the entire troop, consume raw animal flesh, not previously and conveniently killed, butchered, de-haired, de-boned, de-veined, packaged, cooked, and flavored/spiced "meat", the preparation of which disguises its grisly origin from sophisticated humans trapped in their local cultural hypnosis.  The evidence indicates that chimp animal-killing and distribution of the corpse is practiced by a very small percentage of the chimp troop, and this is used to gain sexual favors, humorously like human "dating".  Thus, flesh-consumption in the chimp is a cultural practice, not a natural instinct, exactly as it is in the human.  
    One would hope that anthro-apologists should be able to recognize the profound differences between animal instincts and culture, since culture is their main topic of study, but not recognizing the difference is the core, and fatal, flaw of anthro-apological fanciful musings.

RW> Second, roots are more important in forager diets than they are for other apes
     So what?  This observation would clearly indicate that root-eating is human-cultural, not instinctual among the apes.

RW> Third, although humans are generalists capable of eating a wide range of items ...
     So what?  If the "capability" is strictly due to tool use: hunting and cutting tools, fire, and spices/condiments, as in the case of human meat-consumption, then the practice is strictly cultural in origin, certainly not instinctual.  More confusion of culture and Nature.

RW> ... at any one time foraging populations tend to specialize on a narrow diet breadth
     As do the other apes, and perhaps all animals, consume seasonal items.  So what?  Other such 'specializations' are cultural in origin, thus meaningless in an honest discussion of the natural human diet.  It is a common ploy of the ignorant to make a true statement, and then imply that it has some meaning that is irrelevant and nonexistent.

RW> Fourth, humans employ a variety of novel food-processing techniques that improve food quality in various ways, including elevating energy density and reducing toxins
     Actually, "food-processing techniques" cause a plethora of negative impacts on human health, including the creation of abundant toxins not in the original raw item. 
     Cooking produces some of the most potent carcinogens known, creates hundreds of toxic Maillard reaction chemicals not in the original raw item, denatures proteins, thus making them less digestible or indigestible, releases ~10 times the starch for digestion as available in the raw, chewed starchy item, thus leading to obesity and diabetic issues, enables the consumption of many materials not able to be eaten raw: "meats", grains, beans, legumes, pulses, roots, tough vegetables, ...  
     There is no reason to "elevate energy density" (what does that mean?), especially with rampant human obesity that affects ~66 of US adults.  Overweight does NOT exist, however, if humans who consume mostly, or all, raw foods!
     Therefore, Mr. Wrangham, cooking creates overweight, obesity, and morbid obesity
     All the other apes demonstrate superior health to human apes when consuming their natural diets.  Many more toxins are produced by cooking than are "reduced" by it.  "Meat" consumption results in "degenerative diseases" and enormous costs to society.

RW> These four traits are thought to reflect an evolutionary commitment to a diet of relatively high-calorie items compared to the fruits and foliage that dominate the diets of great apes.
     More bizarre pseudo-science: evolution does not have any "commitments".  
     Consensus science claims evolution happens because of random mutations at the genetic level, and the subsequent filtering out and propagation of the beneficial mutations at the somatic level, by an unexplained process called "reproductive advantage".  For evolution to have any "commitments", evolution would have to have both consciousness and a teleology; these conditions simply do not exist.  
     Notice that there is no logical basis or data supporting this "thought" about "evolutionary commitment".  
     There is a pattern of institutionalized deception clearly apparent in many anthro-apological writings; two techniques are common.  The first three "biologically significant differences" listed above happen to be true, but are totally irrelevant to investigating the biologically-correct diet for the human ape; this gambit creates the illusion that the writer is telling the truth.  We'll call this technique: "the insertion of irrelevant facts".  And, the forth "trait" is just plain wrong and misleading.

RW> Here we propose that cooking represents a fifth important feature of the human diet. Normally cooking is regarded as too novel to have had evolutionary significance.
     Yes, cooking is an "important feature of the human diet" because it directly creates the current plague of "degenerative diseases".
     "Novelty" is not the issue; the issue is whether any species voluntarily abandoning its biologically-correct diet for one with profoundly different chemistry, including the negative biochemical effects of cooking, 10,000 untested food additives, junk and processed foods, and now GMO frankenfoods, can "adapt" to such a fundamental shift in chemical input.  
     "Adapt" means "to make fit"; here "fit" is used in the sense of "fitness"; i.e. health.  
     Let's look at the process by which species "adapt".  Say we have a population of ants and spray them with DDT.  Most will die, but a few that had an inherent resistance to DDT poisoning, developed by random mutations already in their genes when sprayed, will survive.  Their offspring will then have this increased resistance to DDT - the mythical "survival of the fittest".  Spray that new population with more DDT, and some with even more resistance will survive, since more random mutations have provided this capability.  This is the mechanism whereby "super bugs" are created by medical antibiotics and super insects are created by poisoning of agricultural land with pesticides for commercial profit.
     The point here is that the individual does not do anything to "adapt" or develop this fitness, it was inherent in the individual's genes prior to the time of the chemical insult.  
     One will find nothing in contemporary evolutionary texts that claims that any species can make radical changes to its biologically-correct diet and then "adapt" to that changed diet.  For cooking to have a positive "evolutionary significance" there would have to be, created by strictly random mutations, a very complex biochemical system with dozens to hundreds of new biochemical paths, necessary to properly digest, transport, and assimilate cooked foods with widely differing chemistries than the original biologically-correct diet.  And then, properly deal with the plethora of toxins created by the cooking process -- all this incredible complexity pre-developed by individual random mutations, and just waiting patiently for unknown thousands of years for some humans to capture fire and invent cooking.  Then, these "cooked-food genes" would have to be propagated and come to dominate the human gene pool by these "cooked-food gene-individuals" out-breeding the original raw fooders who would then go extinct.  
     Isn't is patently obvious that RW>'s proposed scenario is impossible?  
     Not to anthro-apologists, who are not intellectually-honest enough to look at their own diets with logical dispassion.  

RW> In contrast to that view, ...
     ...held by all contemporary evolutionary theorists.

RW> ... we propose that as a result of a long history of cooking, adaptation has occurred in various human traits concerned both with digestion and with other biological features. However, much remains to be discovered about how humans have adapted biologically to cooking.
     IF our species had "adapted" to cooking, why is there is absolutely no evidence presented that this occurred?  Quite the contrary, why are all the currently-popular "degenerative diseases" highly-correlated with the consumption of cooked foods?  Most are specifically correlated to cooked "meats", which RW> seems to prize highly, for as-yet-unstated reasons.  
     Remember, that to "adapt" is to make fit, or healthy.

2. The distribution of cooking
RW> We define cooking as applying heat to improve the nutritional quality of food. According to this definition, it is normally claimed that all human populations cook.
     Now, that is really humorous; this definition is completely absurd!  We are supposed to believe that Og, the cave man, who had stupidly wandered out of our tropical ecological niche, where our biologically-correct diet items grew abundantly, and into the Frozen North, where there was no fresh fruit, nuts/seeds, or abundant vegetation during the cold months, did proper biochemical/nutritional research and analytically determined that "applying heat" improved "the nutritional quality of food".  
     What absolute nonsense, but anthro-apology is a humorously-entertaining, if not logical, field.
     There is no evidence presented that even suggests that "applying heat to improve the nutritional quality of food".  NONE, but the opposite is true.
     RW> simply defines that "cooking as applying heat to improve the nutritional quality of food".
     Science by definition, a new anthro-apological technique!
     What probably really happened was that someone dropped a hunk of animal flesh into the fire by accident, and when the fire went out so it could be retrieved, it was discovered that the burnt flesh was easier to chew, since the proteins had been denatured and partially hydrolyzed, and it certainly tasted better than raw flesh due to the hundreds of toxic Maillard Reaction products produced by the high temperatures of cooking.  Cooking destroys the biological usefulness of proteins.  
     People cook only because it allows them to eat all sorts of nutritional nightmares not edible raw: animal flesh, grains, beans, woody vegetables, hard roots, ...  Cooking does allow the consumption of a wider variety of items, thus creating the illusion of abundance, but only with well-documented and disastrous long-term health costs.
    Notice the illusory and (intentionally?) misleading "logic": create a false "definition", and then "claim" that somehow this arbitrary, quite erroneous, and totally absurd definition magically determined, by unspecified and mysterious mechanisms, that "all human populations cook" without the tedious and costly necessity of actual field research needed to document "all human populations"!
     RW> an aleged researcherof human populations is apparently qyutw blissfully unaware that there is a growing movement world-wide of people who choose to eat only raw food.

RW> We have searched the literature for challenges to this generalization, not only among farmers and hunter–gathers but also for cases of explorers, adventurers, or warriors.
     So what?  These people, like the Neanderthals, are mindless victims of their cultural programming and have never actually experimented with a raw diet to experience the effects.  Factual, but irrelevant and deceptive, as usual.  Aren't anthro-apologists supposed to understand culture; isn't that supposed to be what they do??

RW> Among contemporary agricultural populations, ‘raw-foodist’ individuals sometimes choose to fore-go cooked food for years at a time (below). Other than these deliberate raw-foodists, we have not found any current or historical examples of individuals or small groups living for more than a few days without access to cooked foods.
     Actually, there are many, many more contemporary raw fooders in non-agricultural populations.
     Many raw food web sites, news groups, and discussion lists exist on the Internet.  For example, Google lists ~1,800,000 hits for "raw food".  And, our expert on human behavior can not find them!!!
     "Agricultural populations" tend to eat heavily the products of their own particular farm.  Are "deliberate raw-foodists" somehow different than, say, accidental raw-foodists?

RW> Contrary to earlier speculation, all recorded hunter–gatherers have known how to make fire.
     Same old factual, but absolutely irrelevant and therefore misleading, trickery: the insertion of irrelevant facts.  
     Anthro-apologists would have no evidence of raw food tribes' existence for the simple fact that they leave no permanent evidence of their raw diets, just as chimps leave no long-term evidence of their raw diets, either.  That is, we could not prove that chimps, other apes, and the great majority of animal species even exist IF we looked only for permanent evidence of their diets, since there obviously is none. The only long-term human dietary evidence is that of fire pits, cutting tools, charred or scrapped bones, so the "investigation technique" is strictly biased in order to find only cooked-food tribes.  
     This is supposed to be "science"? xxxxxxxx

RW> Perhaps the most notable inclusion of raw meat in forager diets was by unacculturated Inuit peoples of Canada and Alaska. The Inuit represent one of the most recently adopted human lifestyles, approximately 4000 years old.
     But, they are among the sickest, most obese, psychologically-dysfunctional, and shortest-lived tribes on the planet, since they foolishly choose to live as far away from our proper ecological niche as possible.   RW> focuses only on what cultural tribes eat, and he intentionally ignores the devastating, well-documented, negative health effects of cultural diets; this dishonesty in the service of his false thesis.

RW> When the explorer Stefansson became the first Westerner to live with unacculturated Inuit, raw blubber was a frequent item of their diet and was reported to be preferred to cooked blubber by at least some people.
     Blubber is pure fat, contains no protein or carbohydrates, and is certainly not "meat", which refers to trimmed, lean muscle tissue.
     "Preferred ... by at least some people".  Another impressive "so what?"  No numbers, as usual, so no real data is presented.  But, why bore people with meaningful facts when fanciful dogma is so much more fun and entertaining?

RW> Cuts of seal-meat and fish could also be eaten raw. But meat, blubber and even blood were sometimes cooked. The ambiguous nature of the evidence is shown by the fact that out of four reports of early contacts with Inuit, three reported that food was generally cooked, while the fourth claimed that food was generally eaten raw. In the absence of quantitative data, we conclude that cooking may have been less important for Arctic hunters than in most societies, but that it was nevertheless practiced regularly.
     So, "in the absence of quantitative data", what is the point of even mentioning this conflicting evidence?  Clearly, all these diets were cultural, requiring tools.

RW> Raw meat may have been specially important in Inuit diets by providing vitamin C, which is normally provided by plant diets
     There is generally no Vit C in animal flesh.  The latest USDA food composition tables lists "beef carcases, lean and fat" as having 0.0 mg Vit-C/100 g product, vs. "oranges, all common varieties" as 53.2.  Meat could not provide adequate amounts compared to our biologically-correct diet.  Notice the always-ambiguous "may have"; nothing specific, all merely unsupported speculation.

RW> Lists of plant foods in hunter–gatherer diets typically include many items that can be eaten raw. For example, Laden and Wrangham (in press) reported that 56% of 48 plant roots eaten by African foragers were sometimes eaten raw. But such items tend to provide snacks rather than meals. More importantly, hunter–gatherers typically cook at least one meal every day, normally in the late afternoon or early evening, whereas snacks during the day are more likely to be eaten raw
     Nothing meaningful, here.

RW> Thus no human populations are known to have lived without regular access to cooked food.
     Yet, there is a rapidly-growing population of health-seekers who intelligently choose to eat only raw food, there are many raw-food discussion lists and web sites on the Internet, and many raw-food schools, lecturers, live-in centers, and communities in the formative stages in many countries are readily available for those who are sincerely interested; RW> could have found them IF he wanted to, but it is a lot easier, and more supportive of his pro-meat-propaganda, to just ignore them.

3. The antiquity of cooking
RW> Despite much discussion about the role of fire in human evolution, cooking is often viewed as irrelevant to human evolutionary biology.
    That is simply because cooking is totally unrelated to the random mutation/reproductive advantage mechanisms that drive evolution.  Any introductory text on evolution theory would make that very clear.

RW> Thus, in many texts about the evolution of humans or their food habits, cooking is not discussed at all.
     "Food habits" do NOT "evolve".  There are no random mutations of "food habits" at the genetic level, there is no "reproductive advantage" to filter out the most "fit" diet.  This is high school biology, apparently abandoned along with the rest of consensus science, for the poetic license necessary to write anthro-apological fantasy scripts.

RW> ... and even authors writing explicitly about the need to understand ‘the nutrition for which human beings are in essence genetically programmed’ have entirely failed to discuss [cooking].
     Well, that is because cooking is clearly not related in the slightest to ‘the nutrition for which human beings are in essence genetically programmed’, as that is raw fruits, leaves, nuts/seeds.

RW> The reason why cooking is ignored in this way appears to be the widespread assumption that it has been practiced for too short a time to have had any impact on biological evolution.
     Time is certainly not the issue here, as is often claimed by meatarian propagandists, there are no genetic mechanisms that relate to voluntary behaviors of the human; that is, evolution occurs by random mutations in the genetic code, NOT by cultural practices of the deluded human.

RW> Here is a typical claim: ‘Once Homo sapiens became established as a distinct omnivorous species, surviving by hunting and gathering, there is no reason to believe that further biological evolution occurred in man’s nutrient needs’
    There is absolutely no evidence that humans are a natural "omnivore".  Some humans are cultural omnivores, as flesh-eating most certainly is taught from generation to generation; however, there is unquestionably no instinct to do so, as there would be if such were a response to a natural nutritional need.

RW> Milton was more specific. She considered that ‘relatively recent changes in certain features of the modern human diet (e.g. cooking of most foods, may, in an evolutionary sense, have occurred so rapidly and so recently that human biology has not yet had time to adapt to them.
    What?  Is she now admitting that we did not "adapt" to cooked foods and "meat"??

RW> Current evidence, however, does not support the notion of cooking as being too recent to have had evolutionary effects.
     There is no evidence or claim in modern evolutionary theory that any species can "adapt" to a radically different diet, both in magnitude and kind of dietary chemicals.

RW> The typical duration of a speciation event is considered to be 15 000–25 000 years, and mammalian species can evolve in as little as 5000 years.
    The old insertion of irrelevant facts gambit, convincing -- huh? .

RW> Human biology is also known to be capable of rapid adaptation and specifically in response to a change in diet.
     An impressively-bold, yet conspicuously-unsupported, claim.

RW> Thus populations with a high frequency of genes responsible for lactose absorption (LA) in adults are those with a history of dairying. Populations are estimated to have adapted biologically to milk-drinking in 5000 years or less (i.e. LA genes increased from 5 to 70% of population).
    In this case, since dairy kills infants outright, such a drift may have indeed occurred; however, more LA genes simply do not address the other significant issues with bovine beverage: bovine growth hormone, agricultural chemicals, antibiotics, casein and casomorphines, 3.2 times the protein than in human milk (thus the rampant obesity of human infants fed cow excretions), 4 times the calcium, and the plethora of other health problems related to cow milk consumption.  IF there were any "adaptation" then these health issues would not exist.

RW> These points suggest that for cooking to have been practiced too recently to have had evolutionary effects, it must have been adopted less than 5000 years ago.
    A masterful piece of ill-logic.

RW> For example it is necessary for the processing of cereal grains, ...
     Another absolute statement that is absolutely wrong; some people sprout grains and eat them raw.  RW> should get out more.

RW> Further back in time, various European and Middle Eastern sites that go back more than 250 000 years ago contain extensive evidence of
hominid use of fire.
     Note how "hominid use of fire" is intentionally confounded with "cooking", but they are quite different, aren't they?

RW> Brace and his colleagues have emphasized the importance of apparent ‘earth-ovens’ from these sites.
     "Apparent" but not really?  Wouldn't evidence of "food" in them be proof positive, but 'apparent'?

RW> They conclude ‘that the application of heat to food, if for no other purposes than to thaw the frozen remainders of yesterday’s haunch, made an important contribution to subsistence at the northern edges of human occupation’.
     But that is in violation of RW>'s previous "definition" of cooking: "applying heat to improve the nutritional quality of food", but when did consistency get in the way of a good anthro-apological yarn?

RW> Cooking is therefore widely accepted back to at least 250 000 years ago
     False conclusion, based on shifting definitions.

RW> Other evidence points to the control of fire by hominids even earlier, such as 400 000–600 000 years ago in Vertesszolos, Hungary, more than 1 million years ago in Swartkrans, South Africa, and 1.6 million years ago at Koobi Fora, Kenya. The oldest date suggested for the adoption of cooking is 1.9 million years ago.
     The old irrelevant fact gambit.  "Control of fire" is not "applying heat to improve the nutritional quality of food"!!

RW> ... a time that marks ... a rise in dietary quality...
    No proof, data, or any support. Unsupported and outrageous assertions are common in anthro-apological scripts.

RW> ..., and a shift towards a human pattern of life-history
     A "human pattern of life-history" - what does this mean??  Humans had non-human patterns of life history, and then adopted human patterns?

RW> Thus the precise date when cooking was adopted is unknown. Nevertheless, cooking is clearly ancient compared to the time required for biological adaptation to occur.
     RW> repeatedly makes the patently-absurd, yet always-unsupported, claim of "adaptation" to cooked foods, yet there is not one scrap of scientifically-credible evidence that any genetic adaptation to voluntary behaviors of individuals is even possible.
     Who was it that said if you tell the same lie often enough, people will start to believe it?

RW> Brace et al. hypothesized that because people could not have survived winters without being able to de-frost meat from kills, cooking became obligatory for hominids occupying glacial zones, 250 000 years ago.
    So what?  Since humans had wandered out of our proper Tropical ecological niche where our true foods grew in abundance, what they were forced to eat to survive is simply irrelevant.

RW> Here we [suggest] that without the use of cooking, most plant foods are not sufficiently digestible, ...
     Now, just HOW do the rest of the plant-eating species on the planet thrive?  RW> is apparently claiming that these uncounted millions of species, both past and present, do and did, not exist?  Wow!  
     The largest land animals that ever existed on this planet, the plant-eating dinosaurs, strangely, found their plant diets to be "sufficiently digestible" and thrived; however, they did not go to Harvard and did not read RW>'s article.  Apparently, that was a good thing for them - that they were oblivious to the fact that their diets were "not sufficiently digestible".

RW> ... and most meat foods are not sufficiently tender.
     Thus, conclusively proving that "meat foods" are not a natural item in our species' diet.  Apparently, RW> believes that two wrongs do make a right?

4. Effects of a raw-food diet
RW> In the only research that we have found of the effects of a raw-food diet, ...
     Only one?  With Harvard's massive resources?  Apparently, no real effort was made in the fear that honest research would undermine the dogma-at-hand?

RW> Even eating these high-quality diets, raw-foodists were vulnerable to energy shortage.
     Strange, just how do the millions of uncounted species of Life currently living on this planet and the countless millions once living here, but now extinct, all thrive on a totally raw diet?  IS RW> claiming that all Life on this planet is, and has always been, "vulnerable to energy shortage"?  Just how was this alleged "energy shortage" determined?  Being true to his style, RW> presents absolutely no credible evidence to support his outrageous and obviously false, claims.

RW> The negative effect of an inadequate energy supply was indicated by women’s reproductive performance, which worsened steadily with larger amounts of raw food. Thus among women on 100% raw-food diets, approximately 50% of women were completely amenorrheic, while a further proportion (not reported) suffered irregular and or incompetent menstrual cycles.
     Here, RW> makes the common mistake of believing that human "menstruation" is a natural and healthful process, when it is merely a cleansing process necessary only in highly-toxic cultural-diet eaters.  The other apes do not menstruate; they have estrus which is absolutely different and 180° out-of-phase with "menstruation".  There is a little booklet titled: "Is Menstruation Necessary?" by Wendy and Nadine for people interested in this effect.  Note, also, that RW> confounds "reproductive performance" with "menstruation", which is obviously very different; but, it does have that emotional impact so critical to propaganda. xxxxxxx

RW> Although this could in theory result from vegetarianism, ...
    Oh, what is that "theory"?  Another outrageous, unsupported claim!  REAL theories are supported by credible data.

RW> ... that ‘a strict raw food diet cannot guarantee an adequate energy supply’.
    Yet, strangely, ALL species of Life ever on this planet evolved and thrived on a "strict raw food diet".  Is RW> claiming that all these species never existed?

RW> ... raises the question of whether people could survive on a raw food diet in the wild.
     You mean like our ancestors did, and the other apes, and all other Life does?

5. Theoretical problems with a raw diet
5.1. Plants
RW> Wrangham et al. noted five ways in which foods are improved or softened by cooking. It can break down physical barriers such as thick skins or husks by softening the cellulose present. It can burst cells, also helped by cellulose softening, making cell contents more easily available for digestion or absorption.
     And, such breaking of cell walls makes ~10 times the starch available for digestion in starchy "foods", such as grains and roots (not really foods for our species), this leading to the obesity and diabetes common in predominately cooked-starch diets.

RW> It can modify the physical structure of molecules such as proteins and starchs, into forms more accessible for digestion by enzymatic degradation.
     Yes, cooking does destroy the physical geometry of "food" molecules, but since digestion requires a precise lock-and-key fit between the digestive enzyme and food substrate, cooking substantially reduces the digestibility of proteins and other important nutrients. xxxxx Pottenger's Cats.

RW> It can reduce the chemical structure of indigestible molecules into smaller forms that can be fermented more rapidly and completely.
     Digestive biochemistry is not "fermentation".

RW> Finally, it can denature toxins or digestion-reducing compounds.
     If it can "denature toxins or digestion-reducing compounds" into biological inactivity, it can also denature into biological inactivity needed nutrients.  Denaturing molecules does NOT selectively destroy toxins and enhance desirable nutrients; it destroys everything.

RW> In their different ways, each of these mechanisms makes food more available, either rendering it palatable or raising its digestibility (defined as the proportion of dry matter intake not present in the feces).
     For a "food" molecule to actually be used as food, it must be digested, absorbed into the blood stream, cross cell walls, and finally participate in internal cellular chemistry; what is in the feces does not relate to what is finally usable in the cells.  Toxic material, or excessive nutrients, are commonly stored in large quantities, such as in "fat" or mucus deposits, thus not present in the feces.  That does NOT mean that such material was "digestible" in a healthy sense.

RW> Modifying the physical structure of macromolecules such as proteins and starches often makes them more accessible to enzymatic digestion.
     Ignoring the profound difference in the effects of such modifications in starch vs. protein vs. fats is a fundamental error. xxxxxx heat on fat

RW> Most types of cooking tend to increase the digestibility of starch, ...
     It does not "increase the digestibility of starch", cooking breaks down the cell walls of plant material, thus exposing more of the contents to digestive enzymes than would chewing, which is rather inefficient.  The "digestibility" of starch remains unchanged; it is the exposure that has changed.

RW> The same is true of plant protein digestibility.
     Absolutely not; digestion occurs because of precise lock-and-key fits between the enzyme and target protein geometry; see any biochem text.  Denature the protein, thus destroying its higher 3-dimensional structures which the enzyme fits, and the protein is less, not more, digestible.  The offensive fecal, urine, and body odors of human meat-eaters, these caused by toxic amines such as indole, skatole, cadaverine, and putrescine are mute, but conclusive, evidence that the meat proteins were not digested and assimilated properly.  IF they were digested, transported, and assimilated properly, there would be no amines in the colon to feed the putrefactive bacteria which produce the offensive odors.  The fact remains, in spite of RW>'s profound ignorance of the effects of various human diets, that the excretions of plant-eating humans do not contain these offensive, toxic compounds.

RW> The effects of cooking on the plant fiber fractions is perhaps even more important. The fiber content and texture influences palatability as well as the rate at which the teeth can process a given food.
     If such changes are necessary to eat the "food", that proves that the item is not a natural one for our species.

RW> This changes the rate of energy intake per minute of eating, and hence the likely rate at which energy can be gained per day.
     Indeed, and cooked food-eaters are the only ones with rampant obesity, and the obesity statistics are skyrocketing!  There are no obese human raw-fooders, nor wild animals that eat raw food; the only obese humans are those eating cooked food!

RW> However, using Zootrition, 2.0 Software to calculate raw food diets and Fuel, 2.3 Nutrition Software to calculate conventional, modern human diets, we suggest that it would be difficult for a woman on a raw food diet to consume enough energy to maintain a regular menstrual cycle.
     Why would any rational person want to use "conventional, modern human diets" as a desirable standard, when they are directly responsible for the current global epidemic of obesity and "degenerative diseases"?  Why would any rational woman want to "maintain a regular menstrual cycle" when this is a pathological manifestation of a highly-toxic body?  Why would any rational woman want to "maintain" the physical and psychological debilitation associated with "menstruation"?  Why does RW> not know that pain and discomfort are manifestations of cultural processes that are in conflict with natural ones?

RW> We assume that she weighs 54.5 kg (120 lbs), and to support a sedentary lifestyle of sleeping, eating, driving, reading, cooking, and some level ground walking. If she ate equal amounts of 10 types of fruits, 10 succulent vegetables and five types of greens commonly available in supermarkets, she would have to eat 200 g of each every day to obtain 2000 kcal and a protein level of 14%.

     Why would one assume that 2000 kcal is a desirable target, since the RDA's are determined by the dietary consumption rates of a sick, obese population.  The RDA's are NOT, as most people assume, nutritional values determined to produce the optimum level of health, they are merely averages of a sick, obese population's consumption habits -- the same ones that made them sick and obese.  Does this make any sense?
     Notice also, that no nuts/seeds, avocados, or bananas are included, since their highly-concentrated nutrients would make attaining the false goal relatively simple.  RW> excluded these common foods in order to make the total food intake appear impossibly high; this, in an effort to support his preconceived 'meat-is-good' doctrine.
     And, what does he mean this time by "a protein level of 14%"?  Is he hopelessly lost in the illusory "percentage of calories from xxx" fallacy?  Since he does not specify the term "%" otherwise, does he think that our overall diet should contain 14 weight % protein, when it should contain about 1/3%?  From the chart, it seems he thinks dry weight has some meaning, when it does not, since it destroys the real nutritional concentrations by removing water; this, similar to the PCF hoax.
     Notice, he swapped %'s again, in the text, without specifying which one he means - this is grade school level incompetence.  And, he does not have the courtesy to explain just what "corrected" means in the table.

RW> This 5 kg of fresh food represents 9.2% of her body weight, not including beverages.
     With 80-90% of raw foods consisting of water, "beverages" are not necessary on a raw diet.

     Get John Coleman's Raw Day spreadsheet, enter a diet, and see some credible numbers.
     Doing so, we find that 200 grams each of only 9 foods, not 25 per RW>'s numbers, far exceed the already excessive RDA's by wide margins.

     In fact, if we normalize on the limiting nutrient, folate, we see that about 1500 grams (3.3 pounds) of food are necessary to meet the RDA's at 100%.  This is not difficult to consume with fruits, vegetables, and nuts/seeds.

     In fact, by cheating a bit - by intentionally choosing the more concentrated nutrient sources, we can get well over the RDA's with only 4 foods, not that I'd recommend such an excessively-concentrated, high protein, diet.  Remember, this is just a numbers game, not an optimum health game.

     Then, normalizing on the least-excessive value, i.e. niacin, we can easily meet all the RDA's with a mere 137 grams of each food.

RW> This is a larger daily weight of food than normally recorded for humans, which raises the possibility that it is unsustainably high (cf. Milton, 2002).
     So what?  RW> states that the dry weight of his diet is ~ 1.3 pounds, not high, at all.  With my chosen-nutrient diet, a mere 548 grams, or 1.2 pounds, of food are needed, and that is fresh weight, not dry weight.  Is 1.2 pounds of fresh food per day "unsustainably high"?  That's less than half a pound in each of three "meals".

RW> This diet also contains a fiber content of 51 g dry wt. (423 g fresh wt.). This level slightly surpasses the fiber amount reported for non-westernized, cooking people (40 g) and is approximately twice as high as the recommended level for western diets.
     I would not call 27.5% "slightly", but who cares about accuracy when one is writing an anthro-apology script?  And, it is generally recognized that western diets are too refined and fiber-free.  Meat, eggs, milk, and cheese, for example, contains no fiber.

RW> Higher amounts of fiber can elevate passage rate, so our model diet would be expected to generate a higher passage rate compared to a cooked-food-eater.
     Indeed, cooked fooders, meat and cheese-eaters particularly, are chronically and severely constipated as evidenced by the "well formed stool" and rampant hemorrhoids and headaches, and they happily gain immediate relief when going raw.

RW> Accordingly, this might reduce the amounts of nutrients the gut can absorb from food as it passes through.
     Since ALL species of Life on this plant evolved on a raw diet, this is a bogus issue.  How can these cooked-food propagandists uniformly ignore the fact that all Life, including our species, evolved on a totally raw diet?  Intellectual dishonesty in the service of anthro-propaganda and one's intentionally-unexamined cultural programming.

RW> However, there have been no controlled experiments to determine the upper levels of fiber to which humans can adapt.
     Here, RW> demonstrates, once again, his complete ignorance of evolutionary processes to even make such a statement.  "Controlled experiments" in "human" "adaptation".  Wow!!  Further, there are no known evolutionary mechanisms whereby any species can "adapt" to a diet radically different, both quantitatively and qualitatively, than its biologically-proper one.

RW> For example, on a cooked, western diet (targeting 30% fat, 15% protein), ...
     Which % is it - this time?  Real weight percentage, dry weight percentage, PCF, "corrected percentage "?  Such sloppy, unspecified and varying, frequently-incorrect, usage of simple grade school arithmetic terms is clearly indicative of an don't-care intellect, an inability to communicate, and an inability to think in an analytical mode.

RW> ... our same sedentary female would need to consume 3.5% of her body wt./day or 1.92 kg of food to obtain 2000 kcal.
     Yet, on a realistic raw diet, she would need to consume only 2.8% of her body weight, and on the chosen-for-effect raw diet, she would need consume only 1% of her body weight.

RW> The raw-foodist hunter–gatherer female would have had to consume foods totaling only 7.6% of her body weight daily (Table 1), ...
     Apparently, "corrected" refers to RW>'s mythical "raw-foodist hunter–gatherer female".

RW> ... we tentatively suggest that it is not possible in view of the adaptations of humans for diets of high caloric density (Milton, 2000, 2002).
     Again, he cites Milton, another irrational, unscientific, meat-propagandizing, anthro-apologist fantasy script writer.

RW> These calculations assume an all-plant diet, so they are not realistic ...
    Actually, they are not realistic because the 2000 kcal reference value is based on modern epidemic-obesity and "degenerative disease"-causing cooked diets.  They are not realistic because, apparently, nutrient-dense foods were intentionally excluded to support the current dogma.  A "realistic" all-plant diet, however, easily provides all the (excessive) RDA's.

RW> ... because hunter–gatherers would have included meat in their diet. If we substitute 250 g of raw, ground venison (at 2.4% fat) ...
     Again, RW> demonstrates his profound lack of comprehension of digestive biochemistry; collagen, the dominant protein in animal bodies is NOT digestible raw, so his hypothetical xxxxxx

for an equivalent amount of plant material in the above raw, wild plant diet, the pre-cooking, hunter–gatherer would have had to consume only 5.4% of her body weight to satisfy daily (sedentary) energy requirements (Table 1). Thus it would appear that adding meat would substantially improve energy intake. However, she would still have been consuming 2.7 kg of raw vegetable matter containing approximately 178 g of fiber (890 g fresh wt.) per day. To compound the problem, it appears that raw and unground meat cannot be chewed at a satisfactory rate (see below). These points suggest that a raw-food diet would present constraints of time and energy for a hunter–gatherer.

5.2. Meat
The factors normally considered to constrain meat-eating by hunter–gatherers are the costs of obtaining it and preparing it to be eaten (hunting, scavenging, and cutting with stone flakes, Stanford and Bunn, 2001). Such problems are not significantly aided by cooking. Likewise the digestibility of meat (up to 100%) is not much affected by cooking. For these reasons little attention has been paid to the possible importance of cooking in facilitating meat-eating for humans. Instead, the relevance of cooking for the evolutionary significance of meat-eating has been discussed largely with respect to the special context of its value in de-frosting large kills (Brace, 1995). However, it has also been suggested that the most significant effect of cooking on meat-eating is tenderizing, because this allows a high rate of intake (e.g. Coon, 1954). The meat of wild tropical and temperate mammals is generally low in fat and rich in collagen, making it tough to chew (Lucas and Peters, 2000). Meat toughness is predictable from the connective tissue content, and accounts for much of the variation in preference among Western consumers (Bender, 1982; Dransfield, 1994; Purslow, 1999). Cooking above 80°C coagulates the connective tissue collagen and hydrolyzes it to a soluble protein (gelatin). This allows muscle fibers to be easily separated, and gives them a short, brittle texture allowing easy mastication (Birch et al., 1986). Cooked meat is therefore much easier to eat than raw meat. We know of no data on how rapidly humans can ingest the raw meat of wild animals. For an estimate of the efficiency of eating raw meat, therefore, we turn to data from chimpanzees (Pan troglodytes). Chimpanzees are a potentially useful model because like Homo, they show no signs of dental adaptation to chewing meat, and in relation to body weight their jaws and chewing teeth are approximately the same size as in humans (between Homo ergaster and H. sapiens, Wood, 1995). Chimpanzees might therefore be expected to chew meat at roughly similar rates to humans. Chimpanzees are also avid predators that eat various wild mammals (mostly monkeys and ungulates) up to approximately 10 kg, always raw and normally freshly killed. They prefer meat that is relatively tender, such as younger prey, and blood, feces, brains and guts (Goodall, 1986). (Tenderness is greater in younger animals, Shorthose and Harris, 1990.) Prey items are sometimes abandoned after the softer parts have been eaten (personal observation). Chimpanzees tend to eat their meat very slowly. Unfortunately exact rates of chewing are difficult to observe in the wild, because prey items tend to be shared among consumers that scatter and hide. However, three well-observed cases that were apparently typical allow us to estimate intake rates. First, Goodall (1986) recorded a large infant baboon prey (Papio anubis) that was eaten for almost 9 h by a single adult male chimpanzee. After he had finished with it the head, arms, legs and part of the torso remained, and were then eaten by others. A large infant (weaned) baboon is estimated to weigh 3.8 kg (Lee, 1991). Second, a mother chimpanzee, her infant son and her lateadolescent daughter fed on a newborn bushbuck (Tragelaphus scriptus) for 4.8 h, at which point the legs (somewhat depleted) and backbone were still held together by skin (Goodall, 1986, p. 296). A new-born bushbuck probably weighs less than 4 kg, given that new-borns of nyala (T. angasi) weigh 5.60 kg and nyala females are 2–4 times the body weight of bushbuck (Lee, 1991; Nowak, 1999). Third, a juvenile red colobus monkey (Colobus badius) that was estimated to weigh 4 kg was chewed for a total of 11.5 ‘chimpanzeehours’ by nine chimpanzees (Wrangham, 1975). Based on these observations, we can estimate the rate of calorie intake for chimpanzees eating raw meat. Assuming that 20% of the prey remained in the case of the baboon and bushbuck, and scoring only adolescent or adult consumers, chimpanzees ate prey animals at a rate of 333–348 g/ h, including skin and bones. From our measurements, red colobus meat contains approximately 3% fat, or approximately 115 cal/100 g. This means that chimpanzees eating red colobus meat would have ingested approximately 382–400 cal/h. Since bone and skin, which have lower caloric value than meat, accounted for much of the carcass weight (perhaps 30–50%), actual caloric intake would be less than 400 cal/h. An upper bound for the rate of energy intake, therefore, is 400 cal/h. The energy requirements for a Homo erectus female have been estimated at 2269–2487 per day (Aiello and Key, 2002). At 400 calyh, a Homo erectus would therefore have had to chew raw meat for 5.7–6.2 hyday to satisfy her daily energy needs, i.e. 47–51% of a 12-h day. While similar to the total amount of time spent feeding by chimpanzees (46.9–55.7%, Wrangham, 1992), this time allocation clearly far exceeds any human value for time spent chewing per day. Note that it does not include the time taken to harvest and prepare the meat. Of course it is highly unlikely that Homo erectus would have survived on meat alone, since large quantities of animal protein unbuffered by fat or carbohydrates are physiologically detrimental (Milton, 1987). The important point, however, is that raw meat appears difficult for a hominoid to eat. Possibly, for instance, chimpanzee molars are poorly adapted for holding and slicing raw connective tissue. Equally, chimpanzee jaw muscles may be too weak to be effective (unlike baboons, which eat meat much faster than chimpanzees, Wrangham, 1975). Accordingly, these calculations imply that for meat to have become an important part of the diet, one of three conclusions is necessary. First, precooking humans might have spent much longer chewing their food than any contemporary populations do. Second, unrecognized differences in mastication efficiency between chimpanzees and pre-cooking humans might have allowed humans to chew meat more efficiently than chimpanzees do. Or third, humans must have had some system for tenderizing meat. The chimpanzee model suggests that the most likely solution is the third. We therefore suggest that an important technique that enabled humans to tenderize meat was cooking. In sum, this discussion suggests that humans are poorly adapted to eating raw meat, and that the adoption of cooking would have facilitated the increased use of meat as a food source.

6. Discussion
6.1. Cooking and the digestive system It might reasonably have been expected that the adoption of cooking would not have led to any changes in human digestion. After all, cooking makes food easier to eat, which means that no special adaptations are required to process cooked food. However, current evidence suggests that humans are capable of living on raw food only under unusual circumstances, such as a relatively sedentary lifestyle in a well-supported urban environment. Important theoretical obstacles to living on raw food in the wild include both the low digestibility of much raw plant food, and the toughness of much raw meat. Cooking has been practiced for enough time to allow evolutionary adaptation. These points suggest that humans are evolutionarily constrained to eating foods that are so digestible and easily chewed that cooking is normally obligatory. They suggest that after cooking was adopted, humans lost the ability to survive on raw food except under unusual circumstances (e.g. eating blubber), perhaps because some of the characteristics needed for eating raw food were unnecessarily costly. The implication is that although the adoption of cooked food imposed no new dietary restraints, it created opportunities for humans to adapt by using diets of high caloric density more efficiently. Selection for such efficiency, we propose, led to an inability to survive on raw-food diets in the wild. Important questions therefore arise concerning what limits the human ability to utilize raw food. The principal effect of cooking considered to date has been a reduction in tooth size and jaw size over evolutionary time. Thus Brace et al. (1991) noted that human molar size started falling approximately 100 000 years ago, and suggested that this was a consequence of eating cooked food. Subsequent population variation in the extent and timing of dental reduction is broadly explicable by regional variation in the times when improvements in cooking technology were adopted (Brace, 1995). It is also possible that the earliest impact of cooking was the reduction of tooth and jaw size that accompanied the evolution of Homo ergaster approximately 1.9 million years ago (Wrangham et al., 1999). If so, the fall in tooth size and jaw size that starts around 100 000 years ago may prove to result from later modifications in cooking technique, such as the adoption of boiling. The evolution of soft parts of the digestive system is harder to reconstruct because they leave no fossil record. Human digestive anatomy differs from the other great apes in ways that have traditionally been explained as adapted to a high meat diet. Differences include the smaller gut volume, longer small intestine, smaller cecum and colon, and faster gut passage rate of humans (Chivers and Hladik, 1984; Martin et al., 1985; MacLarnon et al., 1986; Milton and Demment, 1988; Hladik et al., 1999). All such features are essentially adaptations to a diet of relatively high caloric density, however, and may therefore be at least as well explained by the adoption of cooking as by raw-meat-eating. Testing between the cooking and raw-meat model for understanding human digestive anatomy is therefore warranted. The impact of cooking in drying, detoxifying and enriching foods suggests other areas in which to look for adaptations, including the production of salivary and gastric fluids, the response to chemicals generated by cooking, and the detoxification of chemicals destroyed by cooking. Understanding the effects of adaptation to a cooked diet may be important, for example, for predicting the physiological effects of drugs in humans compared to other primates. But little is currently known about differences in digestive physiology between humans and other apes (Milton, 1999). Further investigation is therefore needed of the ways in which human digestive physiology is constrained by the need for cooked food, especially plant foods.

6.2. Cooking and human evolution
Beyond the digestive system, various evolutionary influences of cooking are expected in the same way as other changes in food supply. Many aspects of species biology are adapted to the nature and distribution of their food supply (e.g. Lee, 1999). Cooking has particularly dramatic effects on the food supply, including softening food, increasing food availability, and forcing food distribution into predictable clumps around fires. Indeed, over evolutionary history the adoption of cooking should probably be regarded as one of the largest ever improvements in dietary quality, and one of the largest ever changes in food distribution and availability. Comparable changes include increased meat-eating, agriculture and animal domestication, all of which have clearly had massive effects. An equivalent magnitude of species adaptations can be expected to have followed the adoption of cooking. For example, cooking seems likely to have influenced life-history. Thus human weaning occurs 30–40% earlier than expected for a primate of our body mass (Low, 2000). No specific suggestions have been made until recently for how juvenile humans were able to find foods sufficiently soft for them to eat (Knott, 2001; Aiello and Key, 2002). We suggest that the adoption of cooking, by making raw foods soft enough for juveniles to chew, may have facilitated the early weaning and short inter-birth intervals that characterize the human life-history (Galdikas and Wood, 1980; Low, 2000). Recent variations in cooking technology are similarly associated with variation in the age of weaning (Bullington, 1991). Humans also have low intrinsic rates of mortality compared to other apes (Hill et al., 2001). If superior diets have enabled humans to maintain a more effective immune system, cooking may have contributed to the evolution of reduced mortality. As a second example, cooking necessitates the collection of food into temporary piles. Food-piles are a novel form of food distribution in comparison with non-human primates, but in other species all such concentrated resources invariably generate competition. This implies that cooking would have
generated new forms of social behavior adapted to regulating the new pressures of feeding competition. Possibly, for example, adult females (the smaller and socially subordinate sex) formed protective alliances with individual adult males, leading to a system of ‘respect-for-possession’ among males and contributing to the sexual division of labor (Wrangham et al., 1999). While such scenarios have yet to be explored in detail, the general point is that the adoption of cooking created a form of food distribution with novel implications for the regulation of social behavior. New forms of social behavior would be supported by modifications in psychological tendency. Like other major changes in dietary distribution, the adoption
of cooking can therefore be expected to have had large ultimate effects on evolutionary psychology.

In sum, cooking appears to be a universal with sufficient evolutionary history to have affected human biology in various ways. It can be expected to have had major effects on digestive biology, as well as other features of human biology affected by the quality, abundance and distribution of the diet. Humans are sometimes claimed to be so inventive that it is meaningless to characterize our species as having experienced any particular environment of evolutionary adaptedness (Potts, 1998; Ehrlich and Feldman, 2003). But while cooking gave humans dietary flexibility, it also constrained our species into being creatures adapted to diets of high caloric density, prepared around temporary food-piles, and committed to the control of fire and the social relations that were therefore necessitated. Cooking may be cultural, but current evidence suggests that its effects have fed back into our biology, and have thereby created constraints that importantly shape and define our evolutionary biology. The nature of those constraints have barely begun to be explored.

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Demons Among Us?
Richard Wrangham's photo
Richard Wrangham

. . . is Professor of Biological Anthropology at Harvard University. His book Demonic Males popularized ideas he has developed in scholarly research focused on the influence of ecology on the evolution of primate social behavior. He has studied chimpanzees in Gombe (with Jane Goodall) and Kibale, vervet monkeys and gelada baboons. With a Ph.D. in Zoology from Cambridge University, England, he makes his home in Cambridge, Massachusetts.
Excerpts3:24 secs

Out of almost 5,000 mammal species in the world, there are only two in which males live with their relatives in social groups and occasionally make trips into neighboring territories to stalk, hunt and kill members of neighboring groups. Chimpanzees are one. Humans are the other. And we are so closely related that a blood transfusion from one species to the other will save a life, if the blood types match.

Dr. Richard Wrangham is a Harvard biological anthropologist who has spent almost 30 years studying chimpanzee cultures in the wild and comparing chimp cultures to human ones. He elaborates on what he's found in Demonic Males, his general audience book, as well as Chimpanzee Cultures, which he edited with a group of internationally distinguished primatologists.

Our violent primate nature, shared with chimpanzees, is bad news, especially when you add that both chimps and humans are extremely sensitive to imbalances of power. Gangs of males -- either kind -- know perfectly well how vulnerable a stranded individual neighbor is. And regularly take advantage of the situation in murderous ways, as has now been repeatedly observed among chimps in the wild. It does not require an anthropologist to observe similar behavior in humans.

But there's good news, too, Dr. Wrangham is quick to point out. Both humans and chimpanzees are strategically very sensible species. We both can - and do - adapt our environments. We can avoid contexts in which violent behavior is likely. And evolution also offers us another model for how primates can behave: bonobos. These are apes who "make love not war."

Professor Wrangham describes both humans and chimps as sexist, but the bonobos are not. Why? For starters, there is increased social pressure from other bonobos in the wild -- they live in much larger groups than do chimpanzees. And bonobo females form strong alliances with the result that females are at least co-dominant with males. Then there's the "copulatory behavior" which is a release for the inevitable pressures of living in groups. Chimpanzees fight, bonobos ... well, you know.

As we begin to pry open the mysteries of what is uniquely human, what we share with our primate relatives, we face a profoundly sad irony. All apes, worldwide, face extinction in the wild. Bonobos are particularly threatened, because their range is limited to the troubled nation of the Congo. But across Africa and Asia, apes are now hunted as "bush meat." People are eating bonobos, chimps and gorillas. At the same time, irresponsible logging companies are clear cutting forests, destroying habitat, at an alarming rate.

We're only beginning to learn from chimpanzee (and bonobo) cultures -- which vary dramatically from one location to the next. But the exploration may be tragically short. We are in the process of eliminating our closest living relatives. Once they're gone, it's forever.

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Cooking up quite a story:
Ape, human theory causes evolutionary indigestion
By William J. Cromie
Gazette Staff

Think about this the next time you're waiting for your burgers to cook on the grill: How was cooking "invented"? Today, all societies depend on cooked food, but when and how did cooking begin?

It's an important question. Cooking played a major role in the development of smaller jaws and teeth, bigger brains, smaller guts, shorter arms, and longer legs, according to Richard Wrangham, professor of biological anthropology at Harvard University. He also believes that cooking is associated with females getting heavier and more fertile. That, in turn, changed mating and social behaviors. Instead of large males beating each other with clubs for the relatively rare privilege of mating, smaller guys mated more regularly and began to dine with the family more often.

There's a lot of agreement among anthropologists that human ancestors were cooking their food as long ago as 250,000 to 500,000 years, but Wrangham and a few of his colleagues see evidence that cooks spoiled the broth as long ago as 2 million years. That's about the time when our ancestors became less like apes and more like humans.

There's more agreement on how cooking started than when. Most anthropologists think bush fires, started by lightning, baked or singed exposed tubers and other roots. Human ancestors tried the fired food and the rest, as they say, is history.

One of the big unknowns in this scenario is when our ancestors started to build their own fires. Many clues point to the conclusion that pre-people lit their own fires about 300,000 years ago, but much less positive evidence hints that they controlled fire a million and a half years earlier. Either way, use of fire for warmth, or to keep away large animals with sharp teeth, would have hastened the origin of roast roots and meat.
The joy of cooking

Whenever its origin, cooking had an enormous impact. Heating food makes it safer, more digestible, and better tasting. Even Charles Darwin thought about this. Cooking, he wrote, provides a means "by which hard and stringy roots can be rendered digestible, and poisonous roots or herbs innocuous." Cooking allows a diner to extract many more calories from a root or thigh than eating it raw.

Wrangham was staring at a fire one evening in his backyard when thoughts about the difficulty of eating raw food ignited the embers of his theory. "I've studied chimps for many years in East Africa," he notes. "To get insight into how they live, I have eaten the same food they do. Chewing raw food requires a lot of work."

Wrangham first reported his theory of fire control in a 1999 scientific paper co-authored with several colleagues, including David Pilbeam, Curator of Paleoanthropology in Harvard's Peabody Museum of Archaeology and Ethnology. They and a few others have continued to expand on the idea of cooking as a much more ancient art than generally believed. They have gathered evidence both from ancient ape-people and modern humans.

Studies of modern food faddists who eat only raw food indicate that it's not a very healthy diet. About a third of such people have chronic energy deficits, according to one study. Half of the women stop menstruating. "And this is under the best possible conditions," Wrangham notes, "when the food is abundant and of good quality."

Less chewing and gnawing would gradually lead to less massive jaws and smaller, rounder teeth. It can also account for reduction of gut and rib-cage size. "You don't need large body chambers to break down stringy carbohydrates," Wrangham says. "And more readily digested food can account for the increased energy needed for fueling a larger brain."

When researchers look for such body and brain changes, they find them in skulls and bones as old as 1.9 million years. This is the time when ape-persons were evolving into Homo erectus, an immediate ancestor of modern humans. As the name implies, H. erectus walked upright. His and her arms were no longer adapted for hanging in trees and their legs were longer. The size of their brain cases almost doubled that of apes.

A most curious and dramatic change also developed in the relative size of males and females. Females became a full 60 percent heavier, drastically reducing the size difference between them and males. "Ape males are 50 to 100 percent larger than ape females," Wrangham points out. But the size difference in Homo erectus was essentially the same as that of modern humans, or about 15-20 percent."

Critics who say the early-cooking theory is half-baked attribute such changes to eating more raw meat. Those who preceded H. erectus, referred to as australopithecines, learned to make better stone weapons and to hunt bigger game. That living style, they insist, could have changed brain and body size.

Ah, but what about the teeth and jaws? Eating raw meat, even when sliced up by a keen stone knife, would result in sharp, spiky dentures, not smaller rounded teeth sculpted by eating softer food.

Then there's the big time gap. Australopithecines scavenged or hunted big game 2.5 million years ago, a half million years or more before H. erectus came on the scene. What happened during the gap? After the dramatic changes of 1.9 million years B.C., no remarkable body shifts took place until roughly 100,000 years ago. If cooking didn't begin until 500,000-250,000 years ago, why are there no prominent changes in face and shape like those that occurred 1.9 million years ago?
Hearth times

All of that is just circumstantial evidence, Wrangham admits. There is no "smoking skewer" to prove H. erectus families gathered around hearths so far back in time.

Evidence most anthropologists feel comfortable with shows that our ancestors in Europe dug oven pits 300,000 years ago. In Africa, small patches of reddened, heavily oxidized soil date from 1.5 million years. Even Wrangham agrees that these spots could be caused by natural changes. However, he notes that "Africans don't use cooking pits today. They cook over campfires, traces of which soon disappear."

Studies now under way may resolve the controversy. Microbits of wood and plant material around the reddened areas could show if these particles came from one kind of bush or tree, which would indicate in-place burning by lightning. If the particles come from diverse sources, that would support the idea of wood being brought from different places to build a campfire. Close examination of "microwear" on fossil teeth might also reveal when our ancestors switched to food softened by cooking.

"The evidence in favor of our theory will get stronger," Wrangham believes.
Cooking heats up mating

Reduction in size difference between early H. erectus males and females resulted in profound differences in mating and social behavior that helped to distinguish humans from their more ape-like predecessors, Wrangham maintains. Among apes, the largest males win battles to impregnate females. That doesn't lead to very frequent mating. Gorillas, for example, have fewer than 20 copulations per birth.

When size is more equal, smaller males get to mate more frequently. For chimpanzees and humans, the mating rate rises to 100 or more copulations per birth. This leads Wrangham to postulate that an important turn toward the current human system of mating took place with the evolution of H. erectus some 2 million years ago, the only known time during evolution when the relative body size of males dropped so markedly.

Cooking meant that food would be brought "home," instead of being eaten on the spot. That must have created the problem of large, lazy males raiding the larders attended only by females. They, in turn, would have reacted by trying to form closer relationships with males who would protect their food stores. One way to do this was to increase their sexual attractiveness, which would have increased the number of matings per pregnancy, reduced competition between males, and led to more pair bonding.
If all this is true, then cooking had a major impact on humanization. As Wrangham puts it: "If the foraging and mating systems of humans were indeed shaped powerfully by cooking, the ancient Greek myth that attributes humanity to the gift of fire may be close to the truth."

Copyright 2002 by the President and Fellows of Harvard C

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THE EVOLUTION OF COOKING: A TALK WITH RICHARD WRANGHAM [2.28.01]

One of the great thrusts of behavioral biology for the last three or four decades has been that if you change the conditions that an animal is in, then you change the kind of behavior that is elicited. What the genetic control of behavior means is not that instincts inevitably pop out regardless of circumstances; instead, it is that we are created with a series of emotions that are appropriate for a range of circumstances. The particular set of emotions that pop out will vary within species, but they will also vary with context, and once you know them better, then you can arrange the context... It's much better to anticipate these things, recognize the problem, and design in advance to protect.

Richard Wrangham: EdgeVideo (3:45 min.)
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Introduction

According to Harvard biological anthropologist Richard Wrangham, almost two million years ago humans emerged from a stock of pre-human apes. Remarkably, our species is still evolving today, faster than ever. "Why we evolved then, and why we are still changing, are problems that shape our souls," he says.

Wrangham believes that humanity was launched by an ape learning to cook. In a burst of evolution around two million years ago, our species developed the family relations that make us such a peculiar kind of animal. Cooking made us women, men and lovers.
"We behave like our two closest relatives," Wrangham says. "Chimpanzees and bonobos, because in spite of first appearances, we face somewhat similar kinds of problems to each of those species. Cooking makes our behavior partly chimpanzee-like because it intensifies a chimpanzee-like division of labor. Self-domestication, on the other hand, makes us bonobo-like by selecting for a youthful psyche. In both cases human behavior echoes the biology of our cousins, though never exactly copying it."

One of Wrangham's central ideas is that we should cherish the parallels between humans and other great apes, because they help us to understand our own behavior. "For all our self consciousness, we humans continue to follow biological rules. Life is easier if we understand those rules. Recognition of the deep contradictions in humanity binds us to our past, and also lights our future."

Other themes to his thinking: "We still have much to learn; We should not be afraid of biology; Dichotomous thinking (e.g. biology vs. culture; women vs. men) is almost always unhelpful "Evolutionary anthropology has excessively neglected females."

— JB

RICHARD WRANGHAM is a professor of biology and anthropology at Harvard University who studies chimpanzees, and their behavior, in Uganda. His main interest is in the question of human evolution from a behavioral perspective. He is the author, with Dale Peterson, of Demonic Males: Apes, and the Origins Of Human Violence.

Richard Wrangham's Edge Bio Page

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Acknowledgments --------- of cooking article
Thanks to Ofer Bar-Yosef, Tom Billings, Randy Collura, Susan Lipson, Martin Muller and Paola Villa for help with literature. Thanks to Jamie Jones, Greg Laden and David Pilbeam for collaboration and C. Loring Brace for comments.
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