The Critical Role Played by Animal Source Foods in Human (Homo) Evolution

Abstract

Wild primates take most of the daily diet from plant sources, eating moderate to small amounts of animal source foods (ASF). Plant materials make up from 87% to >99% of the annual diet of great apes, the closest living relatives of modern humans (Homo sapiens sapiens). Reflecting their close genetic relationship, gut form and nutrient requirements of apes and humans (Hominoidea) are very similar, as is their pattern of digestive kinetics-one predicated on a relatively slow turnover of ingesta. In plant-eating mammals, in contrast to carnivorous mammals, greater body size is associated with lower dietary quality. Turning to ASF as a routine rather than occasional dietary component would have permitted the evolving human lineage to evade the nutritional constraints placed on body size increases in apes. Without routine access to ASF, it is highly unlikely that evolving humans could have achieved their unusually large and complex brain while simultaneously continuing their evolutionary trajectory as large, active and highly social primates. As human evolution progressed, young children in particular, with their rapidly expanding large brain and high metabolic and nutritional demands relative to adults would have benefited from volumetrically concentrated, high quality foods such as meat. Today, many humans, particularly those in high income nations, have a variety of high quality, non-ASF dietary alternatives, but such foods were not generally available to paleolithic human ancestors nor to many people today in low income nations.

The Energetics of Encephalization in Early Hominids

“…The consumption of an energy-dense and nutrientrich diet partially offsets the large, metabolically expensive brain, as has been suggested in other studies (Leonard and Robertson, 1994;Aiello and Wheeler, 1995). These empirical findings support Milton's (2003) hypothesis that increased consumption of meat and energydense plant foods (e.g., fruit) was necessary for humans to overcome the metabolic constraints on brain expansion. These findings do not imply that dietary change was the impetus for brain expansion among hominids; instead, consumption of a high quality diet was likely a prerequisite for the evolution of a large, energetically expensive brain in hominids.…”

“…Great apes obtain nearly all their calories from plant foods and even the most carnivorous species, the common chimpanzee (Pan troglodytes), consumes only 2 to 13% of its calories from vertebrate foods (Stanford, 1996;Milton, 2003). Field studies indicate that meat is a highly desirable food item for many primate species; modest consumption reflects the limited ability of chimpanzees and other primates to obtain large and consistent quantities of vertebrate foods because of high acquisition costs (Milton, 1999).…”

“…It should be noted that certain mammals show considerable plasticity in gut dimensions in response to captive diets or seasonal shifts in diet, although this is not true for all species studied (Chivers and Hladik, 1980;Martin et al, 1985). While only limited research has focused on this issue in primates, Milton (2003) notes that humans and great apes display limited gut plasticity and that genetic factors are likely responsible for the divergent gut dimensions in these groups.…”

Nutritional values of tortoises relative to ungulates from the Middle Stone Age levels at Blombos Cave, South Africa: Implications for foraging and social behaviour

“…Animal resources provide protein, fat, and many essential micronutrients that are not readily concentrated in plants (Cordain et al, 2000b), and which have been important in the hunter-gatherer diet over the course of human evolution (Cordain et al, 2000a;Cordain et al, 2001;Hockett and Haws, 2003;Milton, 2000;Milton, 2003). The most visible source of animal products both ethnographically and archaeologically is from hunted large mammals, but essential micro-and macronutrients concentrated in animal resources are also present in what are often considered ‗gathered' foods: small mammals, fish, shellfish, tortoises, and insects (Bird et al, 2009).…”

The meat-scrap hypothesis: small quantities of meat may promote cooperative hunting in wild chimpanzees (Pan troglodytes)

“…Thus, primates in captivity suffer from health problems when maintained on diets low in B 12 (Hamilton and Busse 1978). Other important micronutrients are B 6 , iron, and zinc, which are also only available in small quantities in plant matter, but are found in very high concentrations in meat (Milton 2003a). Lack of zinc has negative effects on primate health (Altmann 1998).…”