NEWS RELEASE, 6/14/99
Meat-eating was essential for human evolution, says UC Berkeley anthropologist specializing in diet
By Patricia McBroom, Public Affairs
|BERKELEY– Human ancestors who roamed the dry and open savannas of Africa about 2 million years ago routinely began to include meat in their diets to compensate for a serious decline in the quality of plant foods, according to a physical anthropologist at the University of California, Berkeley.
It was this new meat diet, full of densely-packed nutrients, that provided the catalyst for human evolution, particularly the growth of the brain, said Katharine Milton, an authority on primate diet.
Without meat, said Milton, it’s unlikely that proto humans could have secured enough energy and nutrition from the plants available in their African environment at that time to evolve into the active, sociable, intelligent creatures they became. Receding forests would have deprived them of the more nutritious leaves and fruits that forest-dwelling primates survive on, said Milton.
Her thesis complements the discovery last month by UC Berkeley professor Tim White and others that early human species were butchering and eating animal meat as long ago as 2.5 million years. Milton’s article integrates dietary strategy with the evolution of human physiology to argue that meat eating was routine. It is published this month in the journal “Evolutionary Anthropology” (Vol.8, #1).
Milton said that her theories do not reflect on today’s vegetarian diets, which can be completely adequate, given modern knowledge of nutrition.
“We know a lot about nutrition now and can design a very satisfactory vegetarian diet,” said Milton, a professor in the Department of Environmental Science, Policy & Management.
But she added that the adequacy of a vegetarian diet depends either on modern scientific knowledge or on traditional food habits, developed over many generations, in which people have worked out a complete diet by putting different foods together.
In many parts of the world where people have little access to meat, they have run the risk of malnutrition, said Milton. This happened, for instance, in Southeast Asia where people relied heavily on a single plant food, polished rice, and developed the nutritional disease, beriberi. Closer to home, in the Southern United States, many people dependent largely on corn meal developed the nutritional disease, pellagra.
Milton argues that meat supplied early humans not only with all the essential amino acids, but also with many vitamins, minerals and other nutrients they required, allowing them to exploit marginal, low quality plant foods, like roots – foods that have few nutrients but lots of calories. These calories, or energy, fueled the expansion of the human brain and, in addition, permitted human ancestors to increase in body size while remaining active and social.
“Once animal matter entered the human diet as a dependable staple, the overall nutrient content of plant foods could drop drastically, if need be, so long as the plants supplied plenty of calories for energy,” said Milton.
The brain is a relentless consumer of calories, said Milton. It needs glucose 24 hours a day. Animal protein probably did not provide many of those calories, which were more likely to come from carbohydrates, she said.
Buffered against nutritional deficiency by meat, human ancestors also could intensify their use of plant foods with toxic compounds such as cyanogenic glycosides, foods other primates would have avoided, said Milton. These compounds can produce deadly cyanide in the body, but are neutralized by methionine and cystine, sulfur-containing amino acids present in meat. Sufficient methionine is difficult
to find in plants. Most domesticated grains – wheat, rice, maize, barley, rye and millet – contain this cyanogenic compound as do many beans and widely-eaten root crops such as taro and manioc.
Since plant foods available in the dry and deforested early human environment had become less nutritious, meat was critical for weaned infants, said Milton. She explained that small infants could not have processed enough bulky plant material to get both nutrients for growth and energy for brain development.
“I disagree with those who say meat may have been only a marginal food for early humans,” said Milton. “I have come to believe that the incorporation of animal matter into the diet played an absolutely essential role in human evolution.”
Milton’s paper also demonstrates that the human digestive system is fundamentally that of a plant-eating primate, except that humans have developed a more elongated small intestine rather than retaining the huge colon of apes – a change in the human lineage which indicates a diet of more concentrated nutrients.
A critique of:
Department of Environmental Science, Policy, and Management
Division of Insect Biology
University of California, Berkeley
| The following is a line-by-line critique of the article: Milton, K. 1999. A hypothesis to explain the role of meat-eating in human evolution. Evolutionary Anthropology. 8:11-21.
In it, Milton, a physical anthropologist, attempts to “explain” why humans eat animal flesh, and why it “seems mandatory” for “weaned children”.
KM: Primates, particularly humans, are noted for their relatively large brains and considerable behavioral plasticity. In contrast to behavior, morphological structures tend to alter only slowly over time, generally in response to particular selective pressures.
KM: Here I will argue that the pattern of gut anatomy and digestive kinetics characteristic of ancestral Hominoidea imposed certain constraints on their descendents in terms of diet. Meat-eating in the human lineage (Homo spp.) appears to be one way of circumventing these constraints.
KM: SUMMARY OF THE ARGUMENT Extant apes and humans are descended from a common plant-eating ancestor.
KM: Great apes and humans also show similarities in many features of gut anatomy and a similar pattern of digestive kinetics, passing ingesta at a relatively slow rate. This kinetic pattern appears to be a conservative feature of the lineage.
KM: In mammalian herbivores, an increase in body size is generally associated with a decrease in dietary quality. Thus, any hominoid increasing in body size and continuing to focus largely on plant foods is likely to show lowered dietary quality and decreased energetic input per unit of food consumed.
KM: Extant apes and humans show various dietary strategies for dealing with the limitations set by their common pattern of gut anatomy and digestive kinetics.
KM: Over their evolutionary history, orangutans and gorillas appear to have followed a dietary strategy associated with increased body size and lowered dietary quality. Because of their large size, both species can and often do subsist on fairly low quality foods such as mature foliage, bark, and unripe fruits. But they have paid for this compromise in dietary quality. For example, relative to many other anthropoids, orangutans, mountain gorillas, and most lowland gorillas are rather passive primates that lack notable sociality, probably because they lack the energy required for a more active life.
KM: Chimpanzees, on the other hand, have followed a different dietary strategy. Though they have fairly large bodies, chimpanzees, like many cercopithecine monkeys, eat a high-energy diet consisting in large part of ripe fruits. In this manner, though often only with considerable effort, including extensive travel and the occupation of large home ranges, chimpanzees generally are able to secure sufficient high-quality food to maintain their active and highly social lives.
KM: Humans, who are believed to have evolved in a more arid and seasonal environment than did extant apes, illustrate a third dietary strategy in the hominoid line. By routinely including animal protein in their diet, they were able to reap some nutritional advantages enjoyed by carnivores, even though they have features of gut anatomy and digestive kinetics of herbivores.
KM: Using meat to supply essential amino acids and many required micronutrients frees space in the gut for plant foods.
KM: In addition, because these essential dietary requirements are now being met by other means, evolving humans would have been able select plant foods primarily for energy rather than relying on them for most or all nutritional requirements.
KM: This dietary strategy is compatible with hominoid gut anatomy and digestive kinetics…
KM: … and would have permitted ancestral humans to increase their body size without losing mobility, agility, or sociality. This dietary strategy could also have provided the energy required for cerebral expansion.
KM: All extant apes eat strongly plant-based diets composed of the fruits, leaves, flowers, and bark of tropical forest trees and vines. Most apes also consume some invertebrates and, less commonly, vertebrates.
KM: In general, however, the gut anatomy of all extant apes is quite similar. Human gut anatomy is quite similar to that of other extant hominoids. Mitchell remarked that primitive humans were probably omnivorous with a [cultural-ljf] tendency toward carnivory, but pointed out that “the result has not yet been any marked adaptive change in the character of the gut as compared with that of the Anthropoid Apes, although in the latter the diet is omnivorous with the strongest leaning toward the vegetable side.”
KM: In 1904, based on study of the comparative anatomy of the hominoid gut, Elliott and Barclay-Smith suggested that the structure of the human gut actually appeared to be closer to that of a herbivore than an omnivore.
KM: The marked sacculations characteristic of the human and ape colon also support the view that the ancestral line giving rise to all extant hominoids was strongly herbivorous. Further evidence of a plant-based diet for ancestral hominoids comes from the study of dentition, which suggests that many fossil hominoids were largely frugivorous.
KM: Thus, using data from various lines of evidence, there seems to be general consensus that humans come from an ancestral lineage that was strongly dependent on plant foods, and that human gut anatomy is very similar to that of other extant hominoids. Despite this basic similarity, there is one striking difference between the gut anatomy of humans and apes. This difference is in the size relationship of different sections of the gut. In all apes, the greatest gut volume is in the colon (>45% of total), with only about 14 to 29% of the total gut volume in the small intestine. For humans, the greatest gut volume is in the small intestine (>56%); only about 17 to 23% of the total gut volume is in the colon.
KM: Compared to apes, modern humans also have a relatively small total gut for their body size. These size relationships make it clear that among extant Hominoidea, humans are the outlier taxon. This suggests that humans rather than apes have deviated most markedly from the ancestral condition in terms of gut proportions and diet.
KM: However, in comparing gut proportions of apes and humans, … my concern is with the inherited pattern of gut proportions characteristic of all extant apes on the one hand and all modern humans on the other – a proportional relationship that I hypothesize is found in all apes regardless of their environmental circumstances or genetic background and one characteristic of all humans regardless of their environmental circumstances or genetic background. The dominance of the small intestine in humans suggests adaptation to a high-quality diet composed of foods that are nutritionally dense, volumetrically concentrated, and amenable to digestion in the small intestine.
KM: In contrast, dominance of the colon in extant apes suggests adaptation to a diet with considerable refractory plant material that cannot be digested in the small intestine and that passes into the voluminous hindgut, where it is retained while certain essential functions such as fermentation of refractory materials are carried out.
KM: Gut proportions are one factor that can influence digestive parameters and food choices in the natural environment, but another important factor that needs consideration is gut kinetics. Gut kinetics refers to the pattern of movement of ingesta, both particulate and liquid, through the digestive tract.
KM: Milton and Demment examined the pattern of digestive kinetics of common chimpanzees (Pan troglodytes) fed diets of two fiber levels. One diet contained 14% neutral detergent fiber; the other contained 34% neutral detergent fiber. Ingesta passed more rapidly on the high fiber diet (mean transit time = 38 hours on the high-fiber diet and 48 hours on the low-fiber diet. Mean transit time is an estimate of the average time ”particles” of marker take to pass through a system of unknown or undefinable compartments). Because ingesta passed more rapidly when dietary quality was low (high-fiber diet), the chimp gastrointestinal tract had less time to process ingesta flowing through it.
KM: However, because this lower-quality food passed more rapidly, chimpanzees could eat more food per unit of time. With only moderate alterations in dietary quality in the natural environment, the end result of both passage rates in chimpanzees would probably be about the same; that is, chimpanzees would be able to meet their daily requirements for energy and nutrients on both diets.
KM: Extensive work has been carried out on the passage kinetics of humans. For example, a detailed study of human passage kinetics at Cornell University showed a mean transit time of 62.4 hours for subjects on a 0% fiber diet and 40.9 hours for human subjects on a 17.3% fiber diet.
KM: However, an extensive body of data supports the view that in humans higher-quality diets tend to pass more slowly than do fibrous, lower-quality diets.
KM: Relative to wild apes, most human populations eat foods that are amazingly refined, digestible, and calorie-rich, as well as low in plant fiber. In humans, much food preparation (nonsomatic digestion) occurs before a food item is ever brought into contact with the mouth and gastrointestinal tract, a behavior that could ultimately have affected human gut proportions.
KM: However turnover of this high-quality ingesta in humans typically is quite slow.
KM: HOMINOID EVOLUTION Like the Carnivora, extant Hominoidea seem ”stuck” with their ancestral pattern of digestive kinetics and basic features of gut anatomy.
KM: The fossil record shows that during the early to middle Miocene, hominoids reached their greatest level of diversity. In general, Miocene apes were characterized by a frugivorous pattern of molar morphology, though some evidence suggests that larger middle-Miocene apes may have had omnivorous tendencies.
KM: I will compare the dietary niches of extant pongids to illustrate how meat-eating may have permitted human ancestors to overcome the energetic constraints imposed by increasing body size in the hominoid lineage.
KM: Not surprisingly, in view of their size and strongly plant-based diet, gorillas (particularly mountain gorillas) and orangutans are often forced to turn to lower quality plant foods — mature leaves, bark, pith, and unripe fruits –when sufficient ripe fruits and high-quality young leaves are not available.
KM: But many such features appear to be resistant to changes that, at least theoretically, might seem useful.
KM: As discussed, there seems general consensus that extant hominoids come from a strongly herbivorous ancestral lineage.
KM: Although some western lowland gorilla groups at times eat a considerable amount of fruit and may range as far as 2.3km/day, it seems to be generally accepted that lowland gorillas eat more vegetative plant parts than do chimpanzees and fall in an intermediate ecological position between chimpanzees and bonobos on the one hand and mountain gorillas on the other.
KM: In short, even lowland gorillas do not appear to be as active, agile, and socially complex as are members of the genus Pan. I hypothesize that, due to features of their almost exclusively plant-based diet, in combination with features of their common hominoid digestive tracts, energy input in these great apes may often be sufficiently limited such that nonessential behaviors are not favored.
KM: In other words, I do not believe that orangutans and gorillas have sufficient ”extra” energy to be more active and social.
KM: Members of the genus Pan [chimp] eat a specialized diet composed, in large part, of succulent ripe fruits. They supplement this basic fruit diet with select protein-rich young leaves, buds, and flowers, as well as animal matter (particularly invertebrates but also some vertebrates).
KM: WHERE DO WILD CHIMPANZEES GET PROTEIN? The fact that the chimpanzee diet is heavily dominated by fruits raises the question of how these apes obtain the protein they require each day.
KM: Although wild fruits as a class are low in protein, fruits average 6.5 +/- 2.6% protein dry weight (range, 3.2% to 12.6%).
KM: Common chimpanzees, particularly females, also often ” fish” for termites and ants, sometimes devoting hours per day to this activity. This suggests that although termites and ants are small, the nutritive benefits they provide are worth this considerable investment of time.
KM: Gastric (stomach) emptying time in human subjects fed bread diets is 4 to 5 hours.
KM: If a similar gastric emptying rate prevails in wild chimpanzees, they should be able to fill the stomach several times each day, retaining refractory materials (seeds, seed coats, pectic substances, cellulose, hemicelluloses) in the cecum and proximal colon for fermentation activities.
KM: WHY NOT EAT MEAT?
KM: Options for any mammal’s diet are limited. Food has to be either plants or animals or a mix of both, and has to supply all nutrients or their precursors that are essential for that particular animal. What spells the difference between species in terms of diet are the types and proportions of foods from each of these two basic dietary categories that can be efficiently exploited. In terms of gut anatomy and digestive kinetics, meat, at least up to some maximum percentage of diet, should pose no problem for a hominoid.
KM: In captivity, for example, boned meat (raw beef and cooked chicken) was so well digested by common chimpanzees that it typically produced no visible residues in feces.
KM: However, hominoids are not carnivores and have neither the gut anatomy nor digestive physiology of Carnivora. As Speth and Speilman discussed, healthy humans are not known to derive any particular benefit from eating excessive amounts of protein; indeed, some evidence suggests that excessive protein consumption is unhealthy for humans.
KM: Excessive protein consumption ” idles” the body engine faster while producing no demonstrably favorable metabolic effects. In addition to these concerns, catabolizing protein for energy is not practical for mammals such as hominoids if other energy substrates are available, the reason being that the metabolic costs of protein conversion greatly exceed those of converting carbohydrates and fat. Perhaps most important, adult humans apparently cannot catabolize sufficient protein to meet more than 50% of their daily energetic requirements.
KM: Though animal matter presumably did not serve as a primary source of calories for evolving humans, there is no reason why moderate amounts of animal matter could not have been used as an important dietary component if it could be secured.
KM: I depart from those who suggest that meat may have been only a marginal food for early humans. I have come to believe that the incorporation of animal matter into the diet played an absolutely essential role in human evolution, though I leave it to others to determine prey types and sizes, means of procurement, and the like.
KM: Human ancestors appear to have evolved in a somewhat arid, seasonal, and fairly open environment where ripe fruits and young leaves probably were not available throughout the year. Animal protein not only provides all of the amino acids humans require in the proper complements and proportions for human protein synthesis, but also is more efficiently digested than plant protein.
KM: A hominoid would thus need to eat fewer grams of meat to satisfy all protein requirements than it would if protein requirements were being met from plant parts even of very high quality.
KM: Perhaps equally important, animal tissues also supply many essential minerals and vitamins that humans require.
| The following color scheme is used: red for 2-5 times the nutritional content in beef, orange for
5-10 times, yellow for 10-100 times, and green for greater than 100 times the amount in beef.
|energy, Kcal||322||607||573||541||276||271||276||306||360||323||656||884||870||290||316||296||32||energy, Kcal|
|pro, %||25.6||24.4||17.7||24.5||9.1||31.3||9.1||6.2||23.2||6||14.3||22.8||57.5||13.4||9.6||0.4||pro, %|
|fat, %||23.5||56.6||49.7||45.8||7.4||5.2||7.3||0.3||9.7||20.1||66.2||100||49.6||7.7||20.9||1||0.3||fat, %|
|Ca, mg||9||58||975||43||1890||176||1890||625||39||646||176||116||120||57||11||12||Ca, mg|
|P, mg||198||464||629||1174||201||548||201||52||842||105||600||705||118||1677||294||11||P, mg|
|Fe, mg||2.2||3.1||14.6||15||124||53.9||123.6||21.4||6.3||8.7||3.4||6.8||28.5||18.5||1.7||0.2||Fe, mg|
|Na, mg||62||1||11||18||55||391||55||102||12||243||2||3||1048||5||13||7||Na, mg|
|K, mg||347||524||468||807||814||6300||814||1125||892||264||600||689||1363||1485||1534||146||K, mg|
|Mg, mg||24||202||351||535||220||372||220||770||239||1.1||225||354||195||781||132||18||Mg, mg|
|Zn, mg||5.4||3.4||7.8||7.5||6.2||6.1||6.2||5.8||12.3||1.1||4.6||5.1||2||6||7.7||0.1||Zn, mg|
|Cu, mg||0.1||1.0||4.1||1.4||0.9||0.5||0.9||0.6||0.8||0.3||1.8||1.8||6.1||0.7||5.2||0.1||Cu, mg|
|Mn, mg||0||4.3||2.5||3.0||220||1.3||7.9||4.3||13.3||30||0.8||2||1.9||14.2||1.2||Mn, mg|
|Se, mcg||24.1||17||5.7||5.6||4.6||32.3||4.6||7.4||79.2||5.9||2960||59.5||7.2||15.6||136||0.6||Se, mcg|
|Vit A, IU||296||9||380||3800||63,240||3800||530||50||570||767||Vit A, IU|
|Vit E||0.2||2.6||2.3||1.0||1.7||1.7||5||1.7||7.6||192.4||50.3||5||6||0.1||0.1||Vit E|
|Thiamin, mg||0.1||0.2||0.8||0.2||0.5||1||0.5||1.9||0.1||1||2.3||2.4||2.8||0.3||Thiamin, mg|
|Niacin, mg||4.3||0.7||4.5||1.7||4.9||10.4||4.9||0.2||6.8||1.6||1.6||4.5||12.9||34||14.1||0.4||Niacin, mg|
|B-6, mg||0.4||0.6||0.9||0.2||1.2||1.4||1.2||0.3||1.3||1.3||0.3||0.8||0.4||4.1||1||B-6, mg|
|Folate, mcg||8.0||66||97||58||274||1535||274||580||281||93||4||227||94||63||163||14||Folate, mcg|
|B-12, mcg||2.4||B-12, mcg|
|Vit C, mg||0||3.2||1.9||50||149||50||80.8||0.7||1.4||10.1||3.5||1678||Vit C, mg|
|Cholesterol, mg||83||Cholesterol, mg|
| So, the facts indicate that KM’s unsupported claims about the nutritional superiority of “animal tissues” are simply wrong. She could have checked the data, but chose not to in service of the meatarian propaganda campaign.
KM: We need to bear in mind that carnivores and omnivores do not eat only muscle tissue or only muscle and fat but instead eat brains, viscera, bone marrow, the liver, and other organs. These different animal tissues provide different types and proportions of particular essential nutrients. In this sense, the eating of different body parts by a carnivore resembles the feeding behavior of a herbivore, which consumes plant foods of different types to obtain a better dietary mix and thereby improve overall dietary quality.
KM: Humans able to satisfy their total protein and much of their essential mineral and vitamin requirements with animal matter rather than plants would free space in their gut for energy-rich plant foods such as fruits, nuts, starchy roots, other plant parts, or honey.
KM: Jones has pointed out that a disproportionately large number of the major food plants domesticated by humans are cyanogenic. If this is an ancient trend in human food habits, the incorporation of animal protein, with its high methionine content, in the diet of early humans could have had considerably utility. An adequate supply of sulfur-containing amino acids is essential in the detoxification of cyanogenic plant foods. Animal protein may therefore have permitted early humans to use, or to use more heavily, such cyanogenic but energy-rich foods.
KM: Using animal matter primarily to satisfy requirements for essential nutrients and plant foods primarily for energy is a dietary strategy that is compatible with hominoid gut anatomy and digestive kinetics as well as evidence from the human fossil and archeological record.
KM: Such a diet, because of its high quality, would have permitted evolving humans to avoid the constraints gorillas and orangutans suffered as a result of body size increases (lowered dietary quality along with lowered mobility and sociality).
KM: This dietary breakthrough in the human lineage presumably was achieved through both technological and social innovations that permitted early humans to greatly improve their net returns from foraging by simultaneously exploiting foods from two trophic levels while, at the same time, lowering dietary bulk.
KM: One critical aspect of this dietary trajectory is that once animal matter entered the human diet as a dependable staple, the overall nutrient content of plant foods could drop drastically, if need be, so long as the digestible calories were present.
KM: Many underground storage organs, for example, are a rich source of calories but are almost devoid of nutrients; some contain cyanogenic glycosides.
|energy, Kcal||322||25||43||118||105||149||109||74||69||72||65||160||21||36||43||energy, Kcal|
|pro, %||25.6||2.2||1||1.5||1.6||6.4||4.8||2.6||1.7||1.5||4.2||1.4||2.5||1.2||1.6||pro, %|
|fat, %||23.5||0.2||0.2||0.3||0.5||0.6||0.1||0.7||0.2||0.2||0.3||0.2||0.2||0.2||fat, %|
|Ca, mg||9||16||27||17||22||181||128||45||18||41||6||16||114||47||16||Ca, mg|
|P, mg||198||58||44||55||28||153||80||100||27||51||98||27||24||58||40||P, mg|
|Fe, mg||2.2||1.2||0.5||0.5||0.6||1.7||1||1.2||0.5||0.8||2.2||0.3||1.6||0.5||0.8||Fe, mg|
|Na, mg||62||7||35||9||13||17||17||40||13||5||26||14||18||20||78||Na, mg|
|K, mg||347||450||323||816||204||401||568||556||415||308||454||271||82||337||325||K, mg|
|Mg, mg||24||24||15||21||0.4||25||69||23||43||38||25||21||18||23||23||Mg, mg|
|Zn, mg||5.4||0.3||0.2||0.2||0.3||1.2||1.6||0.4||0.3||0.3||0.6||0.3||0.2||0.3||0.4||Zn, mg|
|Cu, mg||0.1||0.1||0.2||0.2||0.3||0.2||0.3||0.2||0.1||0.1||0.1||0.1||0.1||Cu, mg|
|Mn, mg||0||0.2||0.1||0.4||0.4||1.7||0.4||23||0.2||0.2||0.2||0.4||0.2||0.2||0.3||Mn, mg|
|Se, mcg||24.1||0.4||1.1||0.7||0.6||14.2||0.7||0.7||0.7||0.7||0.7||0.7||0.9||0.7||0.7||Se, mcg|
|Vit A, IU||28129||20063||46||19||25||6108||580||38||Vit A, IU|
|Vit E||0.2||0.5||0.2||0.3||0.3||0.4||0.2||0.3||0.3||Vit E|
|Thiamin, mg||0.1||0.1||0.1||0.1||0.1||0.2||0.1||0.2||0.1||0.1||0.1||Thiamin, mg|
|Niacin, mg||4.3||1.4||0.9||0.6||0.7||0.7||0.7||0.4||0.7||0.3||1.7||0.9||0.4||0.7||0.3||Niacin, mg|
|B-6, mg||0.4||0.2||0.1||0.3||0.3||1.2||0.3||0.3||0.2||0.2||0.3||0.1||0.1||0.1||0.1||B-6, mg|
|Folate, mcg||8.0||31||14||23||14||3.0||18||13||11||23||338||27||41||21||109||Folate, mcg|
|B-12, mcg||2.4||B-12, mcg|
|Vit C, mg||0||16.9||9.3||17.1||22.7||31.2||41.9||44||5||3||1.9||20.6||25.8||25||4.9||Vit C, mg|
|Cholesterol, mg||83||Cholesterol, mg|
| Thus, we see that plant roots are generally significantly richer than beef in carbohydrates, fiber, calcium, potassium, magnesium, Vit A, Vit E, thiamin, pantothenic acid, folate, and Vit C. Clearly, they are most certainly not “almost devoid of nutrients” as KM claims, without support!
Further, the protein content is much closer to the human adult need of ~1/3% of the overall diet, beef being pathologically excessive, and plant foods generally do not “need” to be cooked, thus eliminating the highly carcinogenic compounds, such as nitrosamines, that are formed by cooking animal protein and fats. The fat content in plant foods is highly limited, compared to the excessive fat in animal products, and it is not artery-glogging, saturated animal fat, nor does it contain cholesterol whatsoever. And, the iron is non-heme iron, not the carcinogenic heme-iron contained in animal products.
So, once again, objective data exposes the meatarian propaganda to be absolutely false.
KM: Grains, too, are a rich source of calories but most species lack some essential nutrients humans require and many contain cyanogenic glycosides.
KM: But with animal matter in the diet to supply many essential nutrients, including sulfur-containing amino acids, the low nutritional value of some plant foods should not pose a barrier to human feeders as long as the digestible energy is there and any harmful secondary compounds can be detoxified.
KM: Another important aspect of meat-eating concerns the increasing importance, as evolution progressed, of higher-quality, volumetrically concentrated foods for infants and children.
KM: As the World Health Organization states: ”A newborn infant needs dietary protein that contains 37% of its weight in the form of essential amino acids, whereas for adults the figure is less than half – about 15%. This has led many to suspect that protein quality is of limited relevance to adults…. Protein quality is of great importance in rapidly growing young animals which are actively depositing new body protein.”
KM: I depart from those who suggest that meat may have been only a marginal food for early humans. I have come to believe that the incorporation of animal matter into the diet played an absolutely essential role in human evolution.
KM: Current evidence offers strong support for the critical role of micronutrients in the proper development and growth of human infants. The high nutritional value of animal matter, not only as a source of essential amino acids, but also as a concentrated supply of micronutrients, seems particularly critical.
KM: Because of the increase in the ratio of metabolic requirements to gut capacity in homeotherms, [warm-blooded animals] eating a diet high in bulky plant material could pose virtually insurmountable problems for small children, with their high energetic and nutrient demands, as well as large brain relative to body size.
KM: Raw meat, organs, brains, viscera, and bones are concentrated sources of iron, calcium, iodine, sodium, and zinc, vitamin A, many B vitamins, vitamin C and other essential micronutrients, not to mention high-quality protein and fat.
KM: A recent study of factors associated with inadequate childhood growth, size, and health in several third-world nations identified inadequate amounts of particular micronutrients including iron, zinc, calcium, and vitamin B12, rather than an inadequate supply of protein or particular amino acids, as the likely culprits.
KM: Due to their content of available minerals and vitamins, animal foods were recommended to help improve the nutritional status of such children.
KM: If the evolutionary trajectory I have hypothesized was characteristic of human ancestors, the routine inclusion of animal foods in the diets of weaned children seems mandatory. Plant foods selected largely for energy content would not be capable of supplying the essential micronutrients or protein children require for optimal mental development and growth.
KM: Many anthropoids appear to regard invertebrates as highly desirable foods and will heavily exploit them when possible.
KM: For example, Hamilton and coworkers discussed two instances in which chacma baboons largely abandoned the plant component of their diet for days to feed on insect outbreaks. Ayres reported that red howler monkeys in Brazil focused on eating caterpillars when a huge number of them occurred in their forested environment (personal communication). These and other accounts suggest that many anthropoid species like invertebrates and will eat more of them when they can.
KM: As noted, some chimpanzees commit a fair degree of daily foraging time to termite fishing and ant dipping.
KM: Such foods may, however, provide apes with particular essential nutrients that are inadequately supplied by their particular plant-based diets.
KM: Their summary indicates that meat-eating is not a common feature of Old World anthropoid dietary behavior.
KM: One exception is the hunting behavior of some common chimpanzees. Stanford reports that during peak periods of meat eating by chimpanzees at Gombe, some adult male hunters may ingest as much as 500 g of meat per week – a substantial amount. To date, factors contributing to the hunting behavior of chimpanzees are not well understood, but it has been suggested that social factors may be more important than nutritional ones. One key point is that chimpanzees at Gombe rarely appear to set out with the intention of hunting, but typically attacked prey when they fortuitously encounter it during routine foraging excursions.
KM: Given the postulated body and brain size of the earliest humans and the anatomy and kinetic characteristics of the extant hominoid gut, the most expedient dietary avenue open to proto-humans seems to have been to turn increasingly to the intentional consumption of animal matter on a routine rather than a fortuitous basis.
KM: Early humans might have been able to transform a lower-quality plant food into a higher-quality one through technological innovations such as grinding or cooking.
KM: … it seems most expedient to view the earliest humans (Homo) as initially having turned to animal prey to supply the amino acids and many micronutrients they required, using plant foods primarily as an energy source.
KM: Future paleontological and archaeological research, together with closer examination of features of comparative gut anatomy and digestive physiology of Hominoidea and other anthropoids should help to clarify the costs and benefits that were involved in the adaptation of this dietary strategy in the human lineage and to determine how this strategy may initially have been implemented. If the evolutionary trajectory I have hypothesized was characteristic of human ancestors, the routine inclusion of animal foods in the diets of weaned children seems mandatory.
What has caused this profoundly muddled thinking?
—– Original Message —–
Look–if you’re so smart you teach here and I’ll retire and eat
So, she thinks John’s ongoing efforts in personally experiencing a totally raw, frugivorous-ape diet, such as our species evolved on, is “odd”, while her mindlessly following of the local pathogenic, cultural, cooked-meat diet is superior? Apparently, she does not understand cultural anthropology sufficiently to realize that her narrow-minded acceptance of a totally-unnatural meat-based diet was simply programmed into her at a very early age, without her understanding, conscious analysis or decision, by similarly-programmed and similarly-ignorant parents.
So, KM gets an “A” in the creative writing of fiction and academic arrogance, but an “F” in science, open-mindedness, communication, and human relations.
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