Effects of Evolution, Ecology, and Economy on Human Diet: Insights from
Hunter-Gatherers and Other Small-Scale Societies [PDF]
Pontzer & Wood
Annual Review of Nutrition, 2021
The energetics of uniquely human subsistence strategies [Abstract]
Kraft et al.
humans afford expanded energy budgets primarily by increasing rates of energy acquisition, and not through energy-saving adaptations (such as economical bipedalism or sophisticated tool use) that decrease overall costs. Relative to other great apes, human subsistence strategies are characterized by high-intensity, high-cost extractive activities and expanded day ranges that provide more calories in less time. These results suggest that energy gained from improvements in efficiency throughout human evolution were primarily channeled toward further increasing foraging intensity rather than reducing the energetic costs of subsistence.
The evolution and changing ecology of the African hominid oral microbiome [PDF] [Texte]
Yates et al. (Warinner)
We find major taxonomic and functional differences between the oral microbiomes of Homo and chimpanzees but a high degree of similarity between Neanderthals and modern humans, including an apparent Homo-specific acquisition of starch digestion capability in oral streptococci, suggesting microbial coadaptation with host diet.
The evolution of the human trophic level during the Pleistocene [Texte]
Ben-Dor et al.
American Journal of Biological Anthropology, 2021
The evidence shows that the trophic level of the Homo lineage that most probably led to modern humans evolved from a low base to a high, carnivorous position during the Pleistocene, beginning with Homo habilis and peaking in Homo erectus. A reversal of that trend appears in the Upper Paleolithic, strengthening in the Mesolithic/Epipaleolithic and Neolithic, and culminating with the advent of agriculture. We conclude that it is possible to reach a credible reconstruction of the HTL without relying on a simple analogy with recent hunter-gatherers’ diets.
Supersize does matter: the importance of large prey in palaeolithic subsistence and a method for measuring its significance in zooarchaeological assemblages [PDF]
Ben-Dor & Barkai
In Human-elephant interactions, from past to present, Tübingen university press, 2021.
The importance of large prey animals during the Pleistocene and the implications of their extinction on the use of dietary ethnographic analogies [Abstract]
Ben-Dor & Barkai
Journal of anthropological archaeology, 2020
Many hypotheses humans’ evolution and behavior are based on estimates of their trophic level. We introduce an additional factor that should be considered – the availability of large prey animals.
Large prey animals were essential to humans as an economical source of fat and calories. The decline of megaherbivores during the Pleistocene resulted in technological adaptations to the acquisition of smaller prey. The Recent ethnographic dietary record may not be analogous to most of the Pleistocene and may represent adaptations to the end of Pleistocene and Holocene’s prey size decline.
Origins of the Human Predatory Pattern. The Transition to Large-Animal Exploitation by Early Hominins [PDF]
Thompson et al.
Current anthropology, 2019
We propose that the regular exploitation of large-animal resources—the“human predatory pattern”—began with an emphasis on percussion-based scavenging of inside-bone nutrients, independent of the emergence of flaked stone tool use.
New evidence of broader diets for archaic Homo populations in the northwestern Mediterranean [Texte]
Morin et al.
Science advances, 2019
The current consensus in Western Europe is that ungulates formed the bulk of the human diet during the Lower and Middle Paleolithic, while small fast prey taxa were virtually ignored. Here, we present a multisite taphonomic study of leporid assemblages from Southern France that supports frequent exploitation of small fast game during marine isotope stages 11 to 3.
Nutrition and its role in human evolution [Texte]
James et al.
Journal of internal medicine, 2019
More recently, an ability to retain lactase persistence into adulthood has evolved rapidly under the environmental stimulus of pastoralism with the ability to husband lactating ruminants. Increased amylase copy numbers seem to relate to the availability of starchy foods, whereas the capacity to desaturase and elongate monounsaturated fatty acids in different societies seems to be influenced by whether there is a lack of supply of readily available dietary sources of long‐chain polyunsaturated fatty acids. The process of human evolution includes genetic drift and adaptation to local environments, in part through changes in mitochondrial and nuclear DNA. These genetic changes may underlie susceptibilities to some modern human pathologies including folate‐responsive neural tube defects, diabetes, other age‐related pathologies and mental health disorders.
The evolutionary roles of nutrition selection and dietary quality in the human brain size and encephalization [Texte]
Burini & Leonard
It appears that major expansion of brain size in the human lineage is the product of synergistically interacting dietary/nutritional and social forces. Although dietary change was not being the sole force responsible for the evolution of large brain size, the exploitation of high-quality foods likely fueled the energetic costs of larger brains and necessitated more complex behaviors that would have selected for greater brain size.
The cooperative economy of food: Implications for human life history and physiology [PDF]
Karen L. Kramer
Physiology and behavior, 2018
The human diet can be characterized by several common elements. These include diverse, high quality foods, technological complexity to acquire and process food, and the establishment of home bases for storage, processing and consumption. Together these aspects of the human diet challenge any one individual to independently meet all of his or her daily caloric needs. Humans solve this challenge through food sharing, labor exchange and the division of labor. The cooperative nature of the human diet is associated with many downstream effects on our life history and physiology. This paper overviews the constellation of traits that likely led to a cooperative economy of food, and draws on ethnographic examples to illustrate its effects on human life history and physiology.
A brief history of meat in the human diet and current health implications
Neil J. Mann
Meat science, 2018
This ASF intake marked a transition from a largely forest dwelling frugivorous lifestyle to a more open rangeland existence and resulted in numerous adaptations, including a rapidly increasing brain size and altered gut structure.
Hunter-gatherer diets and human behavioral evolution [Abstract]
Physiology and behavior, 2018
Human behavior and physiology evolved under conditions vastly different from those which most humans inhabit today. This paper summarizes long-term dietary studies conducted on contemporary hunter-gatherer populations (sometimes referred to as foragers).
Les gènes FADS (pour Fatty Acid DeSaturase) codent pour les désaturases qui permettent de convertir les acides gras à chaîne courte en acides gras à chaîne longue. En fonction des capacités de conversion, il est plus ou moins facile de se passer d’un apport alimentaire direct d’acides gras à chaîne longue, d’origine animale. Celles-ci ont évolué dans le temps, mais aussi, depuis l’avénement de l’agriculture, sont devenues très hétérogènes parmi les populations humaines.
Dietary adaptation of FADS genes in Europe varied across time and geography [Texte]
Ye et al.
Here we demonstrate, using ancient and modern DNA, that positive selection acted on the same FADS variants both before and after the advent of farming in Europe, but on opposite (that is, alternative) alleles. Recent selection in farmers also varied geographically, with the strongest signal in southern Europe. These varying selection patterns concur with anthropological evidence of varying diets, and with the association of farming-adaptive alleles with higher FADS1 expression and thus enhanced LCPUFA biosynthesis. Genome-wide association studies reveal that farming-adaptive alleles not only increase LCPUFAs, but also affect other lipid levels and protect against several inflammatory diseases.
Des hypothèses intéressantes sur le rôle du nicotinamide (vitamine B3) dans l’évolution humaine, sur la construction du cerveau, mais aussi sur la régulation de la fertilité. Pas mal de corrélations, mais manque de preuves convainquantes.
Meat and Nicotinamide: A Causal Role in Human Evolution, History, and Demographics [PDF]
Williams & Hill
International Journal of Tryptophan Research, 2017
Hunting for meat was a critical step in all animal and human evolution. A key brain-trophic element in meat is vitamin B3 / nicotinamide. The supply of meat and nicotinamide steadily increased from the Cambrian origin of animal predators ratcheting ever larger brains. This culminated in the 3-million-year evolution of Homo sapiens and our overall demographic success. We view human evolution, recent history, and agricultural and demographic transitions in the light of meat and nicotinamide intake. A biochemical and immunological switch is highlighted that affects fertility in the ‘de novo’ tryptophan-to-kynurenine-nicotinamide ‘immune tolerance’ pathway. Longevity relates to nicotinamide adenine dinucleotide consumer pathways. High meat intake correlates with moderate fertility, high intelligence, good health, and longevity with consequent population stability, whereas low meat/high cereal intake (short of starvation) correlates with high fertility, disease, and population booms and busts. Too high a meat intake and fertility falls below replacement levels. Reducing variances in meat consumption might help stabilise population growth and improve human capital.
How our diet changed our evolution [Texte]
Current Biology, 2017
Changes in the human diet have guided the evolution of our metabolism, as several studies of the omega-3 pathway show. As the result of multiple changes and migrations, individuals now carry a patchwork of genetic traits that defines what an individualised healthy diet would look like.
Current views on hunter‐gatherer nutrition and the evolution of the human diet [Texte]
Crittenden & Schnorr
American journal of physical anthropology, 2017
Taken together, both qualitative (summative) and quantitative (population specific) data suggest that there is no one pan‐forager diet, rather there is wide variation based on ecology, seasonality, and resource availability. Moving forward, as foraging populations are rapidly transitioning or have completed the transition, it is essential to acknowledge that rate of change is based not only on ecology, but is also strongly tethered to social, political, and/or economic forces. When attempting to document wild foods still consumed by foragers, it is critical to do so in a way that is both accessible to nutritionists and comparable to previous work done with less nuanced methods.
Metabolic acceleration and the evolution of human brain size and life history [Texte]
Herman Pontzer et al.
In multivariate regressions including body size and physical activity, human TEE exceeded that of chimpanzees and bonobos, gorillas and orangutans by approximately 400, 635 and 820 kcal day−1, respectively, readily accommodating the cost of humans’ greater brain size and reproductive output. Much of the increase in TEE is attributable to humans’ greater basal metabolic rate (kcal day−1), indicating increased organ metabolic activity. Humans also had the greatest body fat percentage. An increased metabolic rate, along with changes in energy allocation, was crucial in the evolution of human brain size and life history.
When man met meat: meat in human nutrition from ancient times till today [PDF]
Baltic & Boskovic
Procedia food science, 2015
There is evidence that meat consumption has had an influence on cranial-dental and intestinal morphologic changes, human erect posture, reproductive characteristics, longer lifespan, and maybe most importantly, on brain and intellectual development
Docosahexaenoic Acid (DHA) : An Ancient Nutrient for the Modern Human Brain [PDF]
Modern humans have evolved with a staple source of preformed docosahexaenoic acid (DHA) in the diet. An important turning point in human evolution was the discovery of high quality, easily digested nutrients from coastal sea food and inland fresh watersources. Multi-generational exploitation of seafood by shore-based dwellers coincided with the rapid expansion of grey matter in the cerebral cortex, which characterizes the modern human brain. The DHA molecule has unique structural properties that appear to provide optimal conditions for a wide range of cell membrane functions
When Did Humans Learn to Boil? [Texte]
John D. Speth
The control of fire and the beginning of cooking were important developments in the evolution of human food-ways. The cooking techniques available to our ancestors for much of the Pleistocene would have been limited to simple heating and roasting. The next significant change in culinary technology came much later, when humans learned to wet-cook (i.e., “boil,” sensu lato), a suite of techniques that greatly increased the digestibility and nu-tritional worth of foods. Most archaeologists assume that boiling in perishable containers cannot pre-date the appearance of fire-cracked rock (FCR), thus placing its origin within the Upper Paleolithic (UP) and linking it to a long list of innovations thought to have been introduced by behaviorally modern humans. This paper has two principal goals. The first is to alert archaeologists and others to the fact that one can easily and effectively boil in perishable containers made of bark, hide, leaves, even paper and plastic, placed directly on the fire and without using heated stones. Thus, wet-cooking very likely pre-dates the advent of stone-boiling, the latter probably rep-resenting the intensification of an already existing technology.
The Importance of Dietary Carbohydrate in Human Evolution [PDF]
Hardy et al.
Quarterly review of biology, 2015
We provide evidence that cooked starch, a source of preformed glucose, greatly increased energy availability to human tissues with high glucose demands, such as the brain, red blood cells, and the developing fetus. We also highlight the auxiliary role copy number variation in the salivary amylase genes may have played in increasing the importance of starch in human evolution following the origins of cooking. Salivary amylases are largely ineffective on raw crystalline starch, but cooking substantially increases both their energy-yielding potential and glycemia. Although uncertainties remain regarding the antiquity of cooking and the origins of salivary amylase gene copy number variation, the hypothesis we present makes a testable prediction that these events are correlated.
Isotope and faunal evidence for high levels of freshwater fish consumption by Late Glacial humans at the Late Upper Palaeolithic site of Šandalja II, Istria, Croatia
Journal of archaeological science, 2015
The site indicate that the main protein source in human diets at this time was freshwater fish, which is in contrast to the vertebrate remains that show a high abundance of large terrestrial herbivores
Carbon isotope ratios of human tooth enamel record the evidence of terrestrial resource consumption during the Jomon period, Japan [PDF]
Kusaka et al.
American journal of physical anthropology, 2015
Reconstruction of the Gravettian food-web at Předmostí I using multi-isotopic tracking (13C, 15N, 34S) of bone collagen [PDF]
Bocherens et al.
Quaternary International, 2015
Strong reliance on mammoth meat was found for the humans of the site, similarly to previously analyzed individuals from other Gravettian sites in Moravia.
Recycling bones in the Middle Pleistocene: Some reflections from Gran Dolina TD10-1 (Spain), Bolomor Cave (Spain) and Qesem Cave (Israel) [Article]
Quaternary international, 2015
It is necessary to distinguish between the use of bone as raw material from pre-existing very large-sized carcasses such as elephants (in cases where it is not certain if these had a nutritional purpose) and the recycling of fragments resulting from bone marrow extraction of smaller mammals that were obtained and consumed by human groups.
Stable Isotope Analyses and the Evolution of Human Diets [PDF]
Margaret J. Shoeninger.
Annual review of anthropology, 2014
Even large-bodied hominoids that could theoretically rely on hard-to-digest C4 plants do not do so. Some Plio-Pleistocene hominins, however, apparently relied heavily on C4 and/or CAM plants, which suggests that they relied extensively on cecal-colon microbial fermentation. Neanderthals seem less carnivorous than is often assumed when we compare their δ15Nbone collagen values with those of recent human populations, including recent human foragers who also fall at or near the top of their local trophic system. Finally, the introduction of maize into North America is shown to have been more sporadic and temporally variable than previously assumed.
Rapid changes in the gut microbiome during human evolution [PDF]
Moeller et al.
Compositional change in the microbiome was slow and clock-like during African ape diversification, but human microbiomes have deviated from the ancestral state at an accelerated rate. Relative to the microbiomes of wild apes, human microbiomes have lost ancestral microbial diversity while becoming specialized for animal-based diets.
Earliest Archaeological Evidence of Persistent Hominin Carnivory [Texte]
Ferraro et al.
Here, we detail three large well-preserved zooarchaeological assemblages from Kanjera South, Kenya. The assemblages date to ∼2.0 Ma, pre-dating all previously published archaeofaunas of appreciable size. At Kanjera, there is clear evidence that Oldowan hominins acquired and processed numerous, relatively complete, small ungulate carcasses. Moreover, they had at least occasional access to the fleshed remains of larger, wildebeest-sized animals. The overall record of hominin activities is consistent through the stratified sequence – spanning hundreds to thousands of years – and provides the earliest archaeological evidence of sustained hominin involvement with fleshed animal remains (i.e., persistent carnivory), a foraging adaptation central to many models of hominin evolution.
Impact of Carnivory on Human Development and Evolution Revealed by a New Unifying Model of Weaning in Mammals
Psouni et al.
PLOS One, 2012
Since early weaning yields shorter interbirth intervals and higher rates of reproduction, with profound effects on population dynamics, our findings highlight the emergence of carnivory as a process fundamentally determining human evolution.
Phylogenetic rate shifts in feeding time during the evolution of Homo [Texte]
Organ et al.
We find that modern humans spend an order of magnitude less time feeding than predicted by phylogeny and body mass (4.7% vs. predicted 48% of daily activity). This result suggests that a substantial evolutionary rate change in feeding time occurred along the human branch after the human–chimpanzee split. Along this same branch, Homo erectus shows a marked reduction in molar size that is followed by a gradual, although erratic, decline in H. sapiens. We show that reduction in molar size in early Homo (H. habilis and H. rudolfensis) is explicable by phylogeny and body size alone. By contrast, the change in molar size to H. erectus, H. neanderthalensis, and H. sapiens cannot be explained by the rate of craniodental and body size evolution. Together, our results indicate that the behaviorally driven adaptations of food processing (reduced feeding time and molar size) originated after the evolution of Homo but before or concurrent with the evolution of H. erectus, which was around 1.9 Mya.
(citée et déformée par Greger)
Studying the Human Gut Microbiota in the Trans-Omics Era – Focus on Metagenomics and Metabonomics [PDF]
Tuohy et al.
Current pharmaceutical design, 2009
Docosahexaenoic Acid and Shore-Based Diets in Hominin Encephalization: A Rebuttal [PDF]
Cunnane et al.
American journal of human biology, 2007
The authors also provide evidence that the fossil record shows that some of the earliest hominins were regularly consuming fish.
Meat in the human diet: An anthropological perspective [Texte]
Journal of dieticians Australia, 2007
Anthropological evidence from cranio‐dental features and fossil stable isotope 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 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 production, lack of ability to chain elongate plant fatty acids and the co‐evolution of parasites related to dietary meat.
Meat made us Human [Google Books]
Henry T. Bunn
In Evolution of the Human Diet: The Known, the Unknown, and the Unknowable, 2006
From the ape’s dilemma to the weanling’s dilemma: early weaning and its evolutionary context [PDF]
Journal of Human Evolution, 2005
The shift in the hominin “prey image” to the carcass and the use of tools for butchery increased the amount of protein and calories available, irrespective of the local landscape. However, this shift brought hominins into competition with carnivores, increasing mortality among young adults and necessitating a number of social responses, such as alloparenting. The increased acquisition of meat ca. 2.6 Ma had significant effects on the later course of human evolution and may have initiated the origin of the genus Homo.
Hunter-Gatherers and Human Evolution [Texte]
Frank W. Marlowe
Evolutionary anthropology, 2005
Ethnographically described foragers may be a biased sample that only continued to exist because they occupied marginal habitats less coveted by agricultural people.3 In addition, many foragers have been greatly influenced by their association with more powerful agricultural societies.4 It has even been suggested that Holocene foragers represent a new niche that appeared only with the climatic changes and faunal depletion at the end of the last major glaciation.5 Despite these issues, the ethnographic record of foragers provides the only direct observations of human behavior in the absence of agriculture, and as such is invaluable for testing hypotheses about human behavioral evolution.
Meat-adaptive genes and the evolution of slower aging in humans [PDF]
Finch et al.
The quarterly review of biology, 2004
We argue that this dietary shift to increased regular consumption of fatty animal tissues in the course of hominid evolution was mediated by selection for “meat-adaptive” genes. This selection conferred resistance to disease risks associated with meat eating also increased life expectancy. One candidate gene is apolipoprotein E (apoE), with the E3 allele evolved in the genus Homo that reduces the risks for Alzheimer’s and vascular disease, as well as influencing inflammation, infection, and neuronal growth. Other evolved genes mediate lipid metabolism and host defense.
The Garden of Eden—plant based diets, the genetic drive to conserve cholesterol and its implications for heart disease in the 21st century [PDF]
Jenkins et al.
Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, 2003
It is likely that plant food consumption throughout much of human evolution shaped the dietary requirements of contemporary humans. Diets would have been high in dietary fiber, vegetable protein, plant sterols and associated phytochemicals, and low in saturated and trans-fatty acids and other substrates for cholesterol biosynthesis. To meet the body’s needs for cholesterol, we believe genetic differences and polymorphisms were conserved by evolution, which tended to raise serum cholesterol levels. As a result modern man, with a radically different diet and lifestyle, especially in middle age, is now recommended to take medications to lower cholesterol and reduce the risk of cardiovascular disease.
Nutritional Ecology and Diachronic Trends in Paleolithic Diet and Health [PDF]
Hockett & Haws
Evolutionnary anthropology, 2003
Modern nutritional studies have found that diverse diets are linked to lower infantmortality rates and longer life expectancies in humans. This is primarily becausehumans require more than fifty essential nutrients for growth and cell maintenanceand repair; most of these essential nutrients must come from outside food sourcesrather than being manufactured by the body itself; and a diversity of food types isrequired to consume the full suite of essential nutrients necessary for optimalhuman health. These principles and their related affects on human adaptations anddemography are the hallmarks of a theoretical paradigm defined as nutritionalecology. This essay applies concepts derived from nutritional ecology to the studyof human evolution. Principles of nutritional ecology are applied to the study of theMiddle-to-Upper Paleolithic transition in order to broadly illustrate the interpretiveramifications of this approach. At any stage in human evolution, those hominidpopulations that chose to diversify their subsistence base may have had a selec-tive advantage over competitors who restricted their diet principally to one foodtype, such as terrestrial mammals.
The Critical Role Played by Animal Source Foods in Human (Homo) Evolution [Texte]
The journal of nutrition, 2003
Carnivory, Coevolution, and the Geographic Spread of the Genus Homo [PDF]
Mary C. Stiner
Journal of archaeological research, 2002
Three zooarchaeological trends reflect important shifts in hominid adaptations over this great time span: (1) increasing predation on large, hoofed animals that culminated in prime-adult–biased hunting, a predator–prey relationship that distinguishes humans from all other large predators and is a product of coevolution with them; (2) greater diet breadth and range of foraging substrates exploited in response to increasing human population densities, as revealed by small-game use; and (3) increased efficiency in food capture, processing, and energy retention through technology, and the eventual expansion of technology into social (symbolic) realms of behavior. Niche boundary shifts, examined here in eight dimensions, tend to cluster at 500 thousand years ago (KYA), at 250 KYA, and several in rapid succession between 50 and 10 KYA.
Dietary lean red meat and human evolution [Abstract]
European Journal of Nutrition, 2000
A study of human and pre-human diet history shows that for a period of at least 2 million years the human ancestral line had been consuming increasing quantities of meat. During that time, evolutionary selection was in action, adapting our genetic make up and hence our physiological features to a diet high in lean meat. This meat was wild game meat, low in total and saturated fat and relatively rich in polyunsaturated fatty acids
Diet and the evolution of the earliest human ancestors [PDF]
Teaford & Ungar
This conclusion runs counter to (i) recent isotope work
suggesting that the australopithecines did in fact consume signifi-
cant amounts of meat (7) and (ii) nutritional work suggesting that
meat may have provided critical nutrients for both young and old
hominids (77–79). There would seem to be three different ways to
reconcile these perspectives. First, the present study has reviewed
only craniodental features related to diet. If the australopithecines
used other means for ingesting and processing meat (e.g., tools),
they might have been able to process meat more efficiently than the
craniodental evidence suggests (80, 81). Second, the heavy C3
signature found in A. africanus (7) may reflect the consumption of
underground storage organs of C3 plants rather than meat (82).
Third, the functional analyses of the teeth assume that all meat has
the same degree of toughness. This may not be the case. Studies of
the physical properties of food have thus far focused on plant
remains, with only brief mention of the toughness of materials like
skin (40, 46). Variations in toughness between animal tissues might
well be due to variations in the arrangement and density of collagen
matrix. Furthermore, the physical effects of decomposition might
render meat less tough and more readily processed by hominids. If
this is so, it could be further evidence in support of scavenging as
part of the early hominid way of life.
An hypothesis to explain the role of meat-eating in human evolution [PDF]
Evolutionary Anthropology Issues News and Reviews, 1999
Human adaptations to meat eating [PDF]
Henneberg et al.
Human evolution, 1998.
It is argued that Homo sapiens is a habitual rather than a facultative
meat eater. Quantitative similarity of human gut morphology to
guts of carnivorous mammals, preferential absorption of haem
rather than iron of plant origin, and the exclusive use of humans
as the definitive host by Taenia saginata and the almost complete
human specificity of T. solium are used to support the argument.
The expensive-tissue hypothesis : the brain and the digestive system in human and primate evolution [PDF]
Aiello & Wheeler
Current Anthropology, 1995
Evolutionary Perspectives on Human Nutrition: The Influence of Brain and Body Size on Diet and Metabolism [Abstract]
Leonard & Robertson
American journal of human biology, 1994
Human dietary patterns and metabolic requirements are com- pared to those of nonhuman primate species in order to gain insights into the evolution of our nutritional needs. In general, primate diet quality (i.e., caloric and nutrient density) is inversely related to body size and total resting metabolic requirements (RMR). Humans, however, consume a diet of much higher quality than is expected for our size and metabolic needs. This energy-rich diet appears to reflect an adaptation to the high metabolic cost of our large brain. Among primates, the relative proportion of resting metabolic energy used for brain metabolism is positively correlated with relative diet quality. Humans represent the positive extreme, having both a very high quality diet and a large brain that accounts for 20-2576 of resting metabolism. Evidence from the hominid fossil record implies that major changes in diet and relative brain metabolism occurred with the emergence of the genus Homo.