Meat in the human diet: an anthropological perspective.KEY POINTS
* Human ancestral diets changed substantially approximately four to five million years ago with major climatic changes creating open grassland environments.
* We developed a larger brain balanced by a smaller, simpler gastrointestinal tract gastrointestinal tract
The part of the digestive system consisting of the stomach, small intestine, and large intestine.
Gastrointestinal tract requiring higher-quality foods based around meat protein and fat.
* Anthropological evidence from cranio-dental features and fossil stable isotope stable isotope
An isotope of an element that shows no tendency to undergo radioactive breakdown. analysis indicates a growing reliance on meat consumption during human evolution.
* Study of hunter-gatherer societies in recent times shows an extreme reliance on hunted and fished animal foods for survival.
* Optimal foraging theory “OFT” redirects here. For other uses, see Office of Fair Trading.
A central concern of ecology has traditionally been foraging behavior. In its most basic form, optimal foraging theory shows that wild plant foods in general give an inadequate energy return for survival, whereas the top-ranking food items for energy return are large hunted animals.
* Numerous evolutionary adaptations in humans indicate high reliance on meat consumption, including poor taurine taurine /tau·rine/ (taw´ren) an oxidized sulfur-containing amine occurring conjugated in the bile, usually as cholyltaurine or chenodeoxycholyltaurine; it may also be a central nervous system neurotransmitter or neuromodulator. production, lack of ability to chain elongate e·lon·gate
tr. & intr.v. e·lon·gat·ed, e·lon·gat·ing, e·lon·gates
To make or grow longer.
adj. or elongated
1. Made longer; extended.
2. Having more length than width; slender. plant fatty acids and the co-evolution of parasites related to dietary meat.
Anthropologists have long recognised that the diets of palaeolithic and recent hunter-gatherers (HGs) represent a reference standard for modern human nutrition and a model for defence against certain Western-lifestyle diseases. Boyd Eaton of Emory University (Atlanta) put this succinctly: 'We are the heirs of inherited characteristics accrued over millions of years, the vast majority of our biochemistry and physiology are tuned to life conditions that existed prior to the advent of agriculture. Genetically our bodies are virtually the same as they were at the end of the palaeolithic period. The appearance of agriculture some 10,000 years ago and the Industrial Revolution some 200 years ago introduced new dietary pressures for which no adaptation has been possible in such a short time span. Thus an inevitable discordance discordance /dis·cor·dance/ (dis-kord´ans) the occurrence of a given trait in only one member of a twin pair.discor´dant
n. exists between our dietary intake and that which our genes are suited to'. This discordance hypothesis postulated by Eaton could explain many of the chronic 'diseases of civilisation'. (1) This review presents an anthropological perspective on what HG populations may have actually eaten.
Contrary to views that humans evolved largely as a herbivorous herbivorous /her·biv·o·rous/ (her-biv´ah-rus) subsisting upon plants. animal in a 'garden of Eden' type of environment, historical evidence indicates a very different reality, at least in the last four to five million years of evolutionary adaptation. It was in this time frame that the ancestral hominid hominid
Any member of the zoological family Hominidae (order Primates), which consists of the great apes (orangutans, gorillas, chimpanzees, and bonobos) as well as human beings. line emerged from the receding forests to become bipedal bipedal adjective Capable of locomotion on 2 feet , open grassland dwellers. This was likely accompanied by dietary changes and subsequent physiological and metabolic adaptations. The evolutionary pressure for some primates to undergo this habitat and subsequent diet change involving open grassland, foraging/scavenging, related directly to massive changes in global climatic conditions, primarily drier conditions followed by worldwide expansion of the biomass of temperate climate (C4) grasses at the expense of wetland forests, (2) accompanied by a worldwide faunal change, (3) including the spread of large grazing animals. Thus, the foods available to human ancestors in an open grassland environment were very different from those of the jungle/forest habitats that were home for many millions of years.
ANCESTRAL DIETS: ANTHROPOLOGICAL EVIDENCE
The lines of investigation used by anthropologists to deduce the evolutionary diet of our evolving hominid ancestors are numerous: (i) changes in cranio-dental features; (ii) fossil isotopic chemical tracer methods; (iii) comparative gut morphology of modern humans and other mammals; (iv) the energetic requirements of developing a large ratio of brain to body size; (v) optimal foraging theory; (vi) dietary patterns of surviving HG societies; and (vii) specific diet-related adaptations. Findings from each of these fields reveal a changing dietary pattern away from low-quality/highly fibrous, energy-poor plant stables to a growing dependence on more energy-rich animal foods, culminating in palaeolithic Homo sapiens being top-level carnivores. (4)
Changes in cranio-dental features
Early hominid fossil remains already show clear cranio-dental changes which indicate a move away from a specialised structure suited to coarse foliage mastication mastication /mas·ti·ca·tion/ (mas?ti-ka´shun) chewing; the biting and grinding of food.
(mas´tikā´sh to a more generalised structure indicative of dependence on fruits and hard nuts but also incorporating changes that indicate meat consumption. Such changes included a decrease in molar teeth size, jaws/skull became more gracile gracile /grac·ile/ (gras´il) slender or delicate.
slender; delicate. , front teeth became well buttressed and shearing crests appearing on teeth, all indicative of less emphasis on grinding and more on biting and tearing of animal flesh. (5)
Fossil isotope ratios
The C13/C12 isotope ratio in fossil remains is indicative of diet, and is a particularly good marker of the intake of broad-leaf plant material versus grasses. Basically, trees, bushes and shrubs use the C3 photosynthetic pathway, which discriminates against the heavier carbon isotope C13 during fixation of C[O.sub.2] compared with the grasses, which use the C4 or Hatch-Slack photosynthetic pathway. (6,7) Examination of early hominid remains indicates that they ate large quantities of the C13-enriched foods. (8) As hominids in general have shown no capacity for digestion of grasses or teeth microwear patterns indicative of grass mastication, (9,10) these hominids were obviously consuming grazing animals existing on the C4 grasses. Similarly, the bone Sr/Ca ratio in mammals shows an inverse correlation with trophic level, with pure carnivores showing the lowest ratio. This pattern is paralleled in fossil remains of palaeolithic fauna, with early hominids showing a Sr/Ca ratio midway between contemporary carnivore carnivore (kär`nəvôr'), term commonly applied to any animal whose diet consists wholly or largely of animal matter. In animal systematics it refers to members of the mammalian order Carnivora (see Chordata). and herbivore herbivore: see carnivore.
Animal adapted to subsist solely on plant tissues. Herbivores range from insects (e.g., aphids) to large mammals (e.g., elephants), but the term is most often applied to ungulates. species. (11,12) These results alone would indicate that even very early hominids consumed a considerable proportion of meat in their diet. (13)
Comparative gut morphology of modern humans and other mammals
Another line of investigation which is useful in ascertaining the dietary preferences and suitability of a species to certain food types is to study the structural features of the gastrointestinal tract. Both pure herbivores (folivores and frugivores) and pure carnivores (such as felids felids
cats. ) have physiological and metabolic adaptations suited to their diet. (14,15) Humans fit neither category, but are truly omnivores, falling between the largely frugivorous frugivorous
fruit-eating. make-up of such anthropoid anthropoid /an·thro·poid/ (an´thro-poid) resembling a human being; the anthropoid apes are tailless apes, including the chimpanzee, gibbon, gorilla, and orangutan.
1. relatives as the chimpanzee and the adaptations of the true carnivores. (16) A sacculated sacculated /sac·cu·lat·ed/ (sak´u-lat?ed) containing saccules.
containing saccules. stomach or well-developed caecum cae·cum
Variant of cecum.
see cecum. and colon are associated with plant-based diets. The lower the plant quality (or the higher the fibre content), the more pronounced are these features. The ruminant ruminant, any of a group of hooved mammals that chew their cud, i.e., that regurgitate and chew again food that has already been swallowed. Ruminants have an even number of toes on each foot and a stomach with either three or four chambers. animals (foregut foregut /fore·gut/ (-gut) the endodermal canal of the embryo cephalic to the junction of the yolk stalk, giving rise to the pharynx, lung, esophagus, stomach, liver, and most of the small intestine. folivores) show the greatest volume in the stomach region. Non-ruminant herbivores (midgut midgut /mid·gut/ (mid´gut) the region of the embryonic digestive tube into which the yolk sac opens and which gives rise to most of the intestines; ahead of it is the foregut and caudal to it is the hindgut. folivores), such as the horse, have greatest development in the caecum and colon. Measures of relationship between gastrointestinal length or surface area, and body length or surface area give a good relative comparison of carnivore versus herbivore characteristics (Table 1).
Carnivores tend to have a well-developed acid stomach and long small intestine small intestine
Long, narrow, convoluted tube in which most digestion takes place. It extends 22–25 ft (6.7–7.6 m), from the stomach to the large intestine. . The human gut with its simple stomach, relatively elongated e·lon·gate
tr. & intr.v. e·lon·gat·ed, e·lon·gat·ing, e·lon·gates
To make or grow longer.
adj. or elongated
1. Made longer; extended.
2. Having more length than width; slender. small intestine and reduced caecum and colon, does not fit any one group but lies between the frugivore fru·gi·vore
An animal, such as a chimpanzee or fruit bat, that feeds primarily on fruit.
[From frugivorous.] and faunivore groups, suggestive of suggestive of Decision making adjective Referring to a pattern by LM or imaging, that the interpreter associates with a particular–usually malignant lesion. See Aunt Millie approach, Defensive medicine. reliance on a high-quality diet in which meat is a predominant component. The size of the human gut relative to body size is also small in comparison with other anthropoids, with a much more pronounced small intestine similar to carnivores. (14,16) Approximate relative proportions of gut volume for humans and some other primates are shown in Table 2.
The energetic requirements of developing a large ratio of brain to body size
Primates in general, and humans in particular, have larger brain sizes than would be expected for their body size (predicted by the Martin equation (18)), a phenomenon described as 'encephalisation'. (19,20) Since the time of Australopithecus afarensis, some four to five million years ago, brain size has increased threefold (Figure 1). What the driving force was for this dramatic increase can only be speculated, although many sound hypotheses based on socio-ecological factors have been put forward.
[FIGURE 1 OMITTED]
Irrespective of the driving force for encephalisation, two critical requirements had to be met: (i) the brain's chemical requirement for long-chain polyunsaturated fatty acid Noun 1. polyunsaturated fatty acid - an unsaturated fatty acid whose carbon chain has more than one double or triple valence bond per molecule; found chiefly in fish and corn and soybean oil and safflower oil (PUFA PUFA polyunsaturated fatty acid.
polyunsaturated fatty acid
polyunsaturated fatty acids. ), particularly arachidonic acid arachidonic acid /arach·i·don·ic acid/ (ah-rak?i-don´ik) a polyunsaturated 20-carbon essential fatty acid occurring in animal fats and formed by biosynthesis from linoleic acid; it is a precursor to leukotrienes, prostaglandins, and (20:4n-6) and docosahexaenoic acid docosahexaenoic acid /do·co·sa·hexa·eno·ic ac·id/ (do-ko?sah-hek?sah-e-no´ik) an omega-3, polyunsaturated, 22-carbon fatty acid found almost exclusively in fish and marine animal oils. (22:6n-3), both of which can only be obtained from animal tissue; (22,23) and (ii) the increased metabolic requirements of a larger brain. (24,25) To sustain such a metabolically expensive large brain, there are two possible evolutionary adaptations that could be used: either elevate the basal metabolic rate basal metabolic rate
Abbr. BMR The rate at which energy is used by an organism at complete rest, measured in humans by the heat given off per unit time, and expressed as the calories released per kilogram of body weight or per square (BMR BMR basal metabolic rate.
basal metabolic rate
n See basal metabolic rate.
basal metabolic rate. ); or compensate for higher brain energy with lower mass-specific metabolic rates of other tissues. The BMR of eutherian mammals is accurately predicted by the Klieber equation, based on body mass, (26) and humans fit this predictive value pre·dic·tive value
The likelihood that a positive test result indicates disease or that a negative test result excludes disease.
a measure used by clinicians to interpret diagnostic test results. well, indicating no increase in basal metabolism basal metabolism: see metabolism. . However, when examining individual organs, the brain mass surplus (and energy requirement) is closely balanced by the reduction in size (and energy requirement) of the gastrointestinal tract (27) (Table 3).
The gut is the only organ which can vary in size sufficiently to offset the metabolic cost of the larger brain. Diets high in bulky food of low digestibility digestibility
the proportion of a feed or diet which can be digested by the normal animal of the subject species.
see digestibility coefficient. require relatively enlarged gut size with voluminous fermenting chambers (rumen rumen
pl. rumens, rumina; the largest of the compartments of the forestomach of ruminant animals that serves as a fermentating vat. It is lined by a keratinized epithelium bearing numerous absorptive papillae; it is partly subdivided by folds (pillars). and caecum). Diets consisting of high-quality foods are associated with relatively small gut size, with simple stomachs, reduced colon size, but proportionately long small intestine (28) as seen in carnivores.
With the relatively poor macronutrient macronutrient /mac·ro·nu·tri·ent/ (-noo´tre-ent) an essential nutrient required in relatively large amounts, such as carbohydrates, fats, proteins, or water; sometimes certain minerals are included, such as calcium, chloride, or sodium. density of wild plant foods, particularly in the open grassland areas, the obvious solution for our ancestors was to include increasingly large amounts of animal-derived food in the diet. (5) The increasing consumption of meat, rich in protein and fats (particularly unsaturated forms), would provide a basis for the threefold increase in human brain size in the last 4.5 million years, from the perspective of both energy supply (25) and brain fatty acid substrate availability. (23)
Optimal foraging theory and food selection
Essentially the subsistence patterns of HGs, early hominids and our palaeolithic ancestors can be explained in terms of cost/benefit analysis. The major survival determinant is daily energy procurement (less energy expenditure). Various models have been developed to explain this phenomenon and loosely described as the 'Theory of Optimal Foraging'. (29) The wild fruits, vegetables, foliage and tuberous roots available to HGs and early hominids were generally fibrous and of low energy density. (30) The high energy/time spent in collection and preparation of such plant foods, particularly seed grains, is not well rewarded in terms of energy gain; hence these are not feasible as a primary energy source (Table 4). This explains why HGs generally have high meat intake despite abundant plant food availability. (32) However, it should not be forgotten that these plants were and are a major source of fibre and micronutrients This is a list of micronutrients.
The study of dietary patterns of surviving HG societies
Calculations have been made from Murdock's Ethnographic Atlas (34) of 229 HG societies, showing that the majority of HG societies obtained [greater than or equal to]56-65% of their subsistence (energy) from animal foods (Figure 2). The predicted macronutrient energy intake ranges were carbohydrate 22-40%, protein 19-35% and fat 28-47%. (35)
Other adaptations and issues related to diet
Similar to obligate obligate /ob·li·gate/ (ob´li-gat) pertaining to or characterized by the ability to survive only in a particular environment or to assume only a particular role, as an obligate anaerobe. carnivores, humans have an inefficient ability to chain elongate plant-rich 18-carbon fatty acids into the 20- and 22-carbon PUFA essential for cell membrane Cell membrane
The membrane that surrounds the cytoplasm of a cell; it is also called the plasma membrane or, in a more general sense, a unit membrane. This is a very thin, semifluid, sheetlike structure made of four continuous monolayers of molecules. function and brain tissue, (36) hence requiring direct consumption from animal tissue. Likewise, humans have inherited a very decreased ability to synthesise taurine from precursor amino acids. (37) The proposed rationale, as for obligate carnivores, is that there was reduced selective pressure to synthesise taurine in vivo in vivo /in vi·vo/ (ve´vo) [L.] within the living body.
Within a living organism.
in vivo adv. because exogenous dietary sources of preformed taurine (found only in animal tissue) were being consumed for a lengthy time period. Physiologically haem haem
see heme. and other porphyrine iron-rich compounds derived only from meat are absorbed by humans in preference to ionic forms of iron, whereas herbivorous animals cannot absorb these haem complexes and rely on absorption of ionic iron. (38) Finally, mammalian hosts and their various parasites undergo close co-evolution. Cestodes of the family Taeniidae are parasites of carnivores spread by eating meat. Taenia saginata Taenia sag·i·na·ta
A tapeworm that is parasitic in humans and is acquired by eating infected beef that is insufficiently cooked. and T. solium use humans exclusively as their host, indicating a substantial period of co-evolution and meat consumption by humans and their ancestors. (17)
THE TRANSITION TO AGRICULTURE AND BEYOND
The dietary changes involved with the transition from hunting and gathering to agriculture have been extensively reviewed. (39-41) This transition began in the Near East approximately 10 000 years ago with the growing of wild cereal crops as a response to population increase and/or scarcity of large mammalian wild game. The transition, however, was associated with physiological stresses, including reduced stature, osteomalacia osteomalacia /os·teo·ma·la·cia/ (os?te-o-mah-la´shah) inadequate or delayed mineralization of osteoid in mature cortical and spongy bone; it is the adult equivalent of rickets and accompanies that disorder in children. , dental caries caries
or tooth decay
Localized disease that causes decay and cavities in teeth. It begins at the tooth's surface and may penetrate the dentin and the pulp cavity. and various nutritional deficiencies, and infectious disease Infectious disease
A pathological condition spread among biological species. Infectious diseases, although varied in their effects, are always associated with viruses, bacteria, fungi, protozoa, multicellular parasites and aberrant proteins known as prions. . (42) The archaeological evidence indicates a shift from consumption of hoofed mammals (gazelle gazelle, name for the many species of delicate, graceful antelopes of the genus Gazella, inhabiting arid, open country. Most gazelles are found only in Africa, but several species range over N Africa and SW Asia; the Persian, or goitered, gazelle ( , antelope and deer), root plants, wild pulses, various nuts and fruit, to a more narrow diet of cultivated wheat, barley, oats oats, cereal plants of the genus Avena of the family Gramineae (grass family). Most species are annuals of moist temperate regions. The early history of oats is obscure, but domestication is considered to be recent compared to that of the other , rice or corn, depending on location. (43) This transition also corresponded with a fundamental reversal of the high-protein, low-carbohydrate diet of the previous HG societies, along with the shift in fatty acid intake type.
With the shift away from the HG dietary pattern and the high reliance on meat in the diet to a more grain-rich diet, the dietary fat intake profile of humans changed significantly. The P : S dietary ratio has dropped drastically from 1.4:1 to 0.4:1, (1) and the n-6 : omega-3 ratio increased from approximately 3:1 to greater than 12:1 in the current Western diet, where the n-6 PUFA from seed oils are now abundant in the diet. (44) Similarly, many micronutrient mi·cro·nu·tri·ent
A substance, such as a vitamin or mineral, that is essential in minute amounts for the proper growth and metabolism of a living organism. intake levels likely dropped following the shift to agriculture and further subsequent developments in food processing and mass production during the industrial revolution some 200 years ago and, more recently, the 'fast-food revolution' (1) as indicated in Table 5.
[FIGURE 2 OMITTED]
With the industrial revolution came more efficient milling methods which separated the fibre-rich bran and nutrient-dense germ of the various grains from the starch-rich endosperm. The range of new products expanded rapidly based on these refined grains and the flour made from them. Similarly, the mass production of nutrient-poor refined sugar cane became common. (46) In more recent times, particularly the last 50-60 years beginning in the USA, we have been exposed to what has loosely been termed the 'fast-food revolution'. This encompasses such aspects of modern Western diet as: (i) the proliferation of take-away food outlets with their ready-to-eat, well-advertised, fat- and energy-rich commodities, usually poor in micronutrients and often filled with high-glycaemic-index (GI) processed carbohydrates; and (ii) the broad range of processed packaged ready-to-heat and serve foods that occupy the expanding aisles of the local supermarket. These also are generally nutrient-poor and energy-rich, and come with little need for concomitant energy expenditure. (46)
The increased contribution of carbohydrate from grains to the human diet following the agricultural revolution has effectively diluted the protein content of the human diet. Whether current protein intakes are below the ideal is a question now being asked, especially in regard to effects on satiety satiety
being in a state of satiation; in experimental animals used with reference to eating and drinking.
located in the ventromedial hypothalamic nucleus. and rates of obesity. Another issue to bear in mind is that 'optimal foraging', which shaped primitive diets, does not apply in the modern era. Today survival does not demand energy-dense, high-fat foods. In fact, it is clear that these foods need to play a reduced role in societies where dietary energy is available in abundance and concomitant energy expenditure is limited.
The type of fat in modern diets is distinctly different from that eaten by our forebears. In particular, saturated fat and n-6 PUFA (from seed oils and grains) have increased at the expense of omega-3 fats from fish and red meat. The cardioprotective effects of long-chain omega-3 fats and their preferential incorporation into the tissues of the body support the notion that modern diets are deficient in these nutrients.
Carbohydrates in the modern diet are also very different from those that HGs ate. Today the majority of dietary carbohydrates are derived from processed cereals and can be of high GI. Cereals were seldom eaten by HGs due to the small size of wild seeds and the degree of difficulty in collecting them. It has been argued that the replacement of protein from meat and fish with high-GI carbohydrates from starch and sugars may have implications for insulin resistance and the development of type 2 diabetes--a condition unknown in HG societies.
There may be more certainty about the impact of reduced intakes of fish and meat on iron and zinc status. Humans evolved on dietary intakes of these minerals, which were several times the current intake. (1) It should come as no surprise that these two nutrients are limiting in the diet of sections of the Australian population today who do not consume red meat. (45) Likewise, the low vitamin B12 status of vegetarians testifies to past reliance on meat in the diet. (47)
Plant foods most likely provided the bulk of micro-nutrients and fibre in the 'palaeolithic' diet; thus, it should be realised that humans were not carnivores, but rather true omnivores, as revealed by numerous lines of investigation including gut morphology studies. The need for a wide variety of nutrient-dense vegetables and fruits and (low-GI) wholegrains in our diet is of importance. However, our pre-agricultural ancestors' basic energy, protein, long-chain fatty acids, vitamin B12, iron and zinc supply came from meat. Thus, adaptations to such a dietary pattern accumulated in our bodies over approximately three to four million years of relatively high meat intake and minimal grain intake. It is argued that the modern Western divergence from this dietary pattern forms the basis of lifestyle diseases that we now face. Thus, there is no historical or valid scientific argument to preclude lean meat from the human diet, and a substantial number of reasons to suggest it should be a central part of a well-balanced diet. (48)
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Medicine. the study of diseases from former times as found in fossils and mummified remains. at the Origins of Agriculture. New York: Academic Press, 1984; 51-73.
40 Hillman GC, Colledge SM, Harris DR. Plant food economy during the Epipalaeolithic period at Tell Abu Hureyra Tell Abu Hureyra ("tell" is Arabic for "mount") was a site of an ancient settlement in the northern Levant or western Mesopotamia. It has been cited as showing the earliest known evidence of agriculture anywhere. , Syria. Dietary diversity, seasonality and modes of exploitation. In: Harris DR, Hillman GC, eds. Foraging and Farming, the Evolution of Plant Exploitation. London: Unwin-Hyman, 1989; 240-68.
41 Ulijaszek SJ. Human dietary change. Philos Trans R Soc Lond 1991; 334: 271-9.
42 Cohen M. Health and the Rise of Civilization. New Haven, CT: Yale University Press, 1989.
43 Van Zeist W, Bakker-Heeres JA. Some economic and ecological aspects of the plant husbandry of Tell Aswad. Paleoorient 1979; 5: 161-9.
44 Sincalir AJ, O'Dea K. Fats in human diets through history. Is the Western diet out of step in reducing fat in meat animals. In: Wood G, Fisher G, eds. Reducing Fat in Meat Animals. New York: Elservier, 1990; 1-47.
45 McLennan W, Podger A. National Nutrition Survey of Australia 1995: Nutrient Intakes and Physical Measurements. Canberra: Australian Bureau of Statistics The Australian Bureau of Statistics (ABS) is the Australian government agency that collects and publishes statistical information about Australia and its people. Population and Housing
The agency undertakes the Australian Census of Population and Housing. , Commonwealth Department of Health and Aged Care, 1998.
46 Cordain L, Eaton SB, Mann NJ et al. Origins and evolution of the western diet: health implications for the 21st century. Am J Clin Nutr 2005; 81: 341-54.
47 Mann N, Li D, Dudman N et al. The effect of diet on plasma homocysteine Homocysteine Definition
Homocysteine is a naturally occurring amino acid found in blood plasma. High levels of homocysteine in the blood are believed to increase the chance of heart disease, stroke, Alzheimer's disease, and osteoporosis. concentration in healthy male subjects. Eur J Clin Nutr 1999; 53: 895-9.
48 Mann NJ. Dietary lean red meat and human evolution. Eur J Nutr 2000; 39: 71-9.
This section introduces meat in the context of the Australian diet. The reviews draw on knowledge from a range of sources and put forward perspectives on how meat has taken its place in the Australian cuisine over time. Mann and Tapsell refer to the scientific literature to present views on meat in the diet from a perspective of evolutionary development and food habits, respectively. Dang dang
Used to express dissatisfaction or annoyance.
adv. & adj.
tr.v. danged, dang·ing, dangs
n. provides a personal commentary based on observations from 30 years of qualitative research associated with the food industry
School of Applied Sciences, RMIT RMIT Royal Melbourne Institute of Technology University, Melbourne, Victoria, Australia
Table 1 Quantitative comparison of length and surface area of gastrointestinal tracts of some animals and humans Intestinal length: body Gastrointestinal surface area: body Species length surface area Cattle 20:1 3.0:1 Horse 12:1 2.2:1 Baboon 8:1 1.1:1 Dog 6:1 0.6:1 Human 5:1 0.8:1 Cat 4:1 0.6:1 Adapted from Henneberg et al. (17) Table 2 Relative gut volume proportions for a selection of primate species (% of total volume) Species Stomach Small intestine Caecum Colon Gorilla 25 14 7 53 Orangutan 17 28 3 54 Chimpanzee 20 23 5 52 Gibbon 24 29 2 45 Human 17 67 NA 17 Adapted from Milton. (14) NA = not applicable. Table 3 Observed and expected organ mass and metabolic rates in humans Mass (kg) Metabolic Tissue Observed Expected Difference Increment (Watt) Brain 1.30 0.45 +0.85 +9.5 Heart 0.30 0.32 -0.02 -0.6 Kidney 0.30 0.24 +0.06 +1.4 Liver 1.40 1.56 -0.16 -2.0 Gastrointestinal 1.10 1.88 -0.78 -9.5 tract Adapted from Aiello and Wheeler. (20) Based on a-65 kg human. Table 4 Energy return rates from foraged and hunted foods by South American hunter-gatherers Food Food type Return rate (kcal/hour) Peccary Animal 65000 Antelope Animal 16000-32000 Rabbit Animal 13500-15400 Paca Animal 7000 Coati Animal 7000 Squirrel Animal 5400-6300 Roots Plant 1200-6300 Fruits Plant 900-6000 Armadillo Animal 5900 Snakes Animal 5900 Birds Animal 4800 Lizards Animal 4200 Seeds Plant 500-4000 Adapted from Cordain et al. (31) Table 5 Estimated daily palaeolithic intake of selected nutrients compared with current US intakes Palaeolithic Australian Nutrient intake (a) US intake (a) intake (b) Macronutrients (% energy) Protein 37 15 17 Carbohydrate 41 51 46 Fat 22 34 33 P : S ratio 1.4 0.4 0.4 Vitamins (mg/day) Riboflavin 6.5 1.3-2.1 2.1 Folate 0.36 0.15-0.21 0.27 Thiamine 3.9 1.1-1.8 1.7 Vitamin C 604 77-109 120 Vitamin A (RE) 2870 1170-1429 1165 Vitamin E 32.8 7-10 NR Minerals (mg/day) Iron 87 10-11 14 Zinc 43.4 10-15 12 Calcium 1956 750 875 Sodium 768 4000 NR Potassium 10500 2500 3317 Fibre (g/day) 104 10-20 23 (a) Adapted from Eaton et al. (1) (b) Adapted from McLennan and Podger, (45) results shown are for combined men and women aged 25-44 years. NR = not recorded in Australian National Nutrition Survey 1995, RE = retinol equivalents.