Primate Origins, Evolution, and Diets
Primate Characteristics
Food-acquisition strategies may be studied from an evolutionary perspective. Although all life shares a common ancestry, evolution has produced too many species to permit global treatment. An apt starting point is our order, the primates, whose hallmarks include possession of nails rather than claws and flexible hands and feet capable of grasping objects like branches, an adaptation to arboreal life. Primates have large heads relative to the body. The skull houses a sizable brain, prompting the inference that primates are intelligent. Primate behaviors appear to corroborate this notion. Nevertheless, the study of intelligence is inexact because this trait is not easy to quantify even among humans. Primates tend to be helpless as newborns because their large brain is immature at birth, necessitating parental care. Intelligence and parent-child bonds facilitate sociability. Primate eyes are close together, permitting binocular vision. Relative to other animals, especially insects, primates live long lives. A person may surpass a century, though such longevity is uncommon. Being mammals, primates have fur (hair) rather than scales or feathers, though humans have less than other primates.
The Necessity of Comparing Kindred Primates
Primates number between roughly 230 and 270 species.9 Precision is elusive because taxonomists cannot always agree whether similar individuals are alike enough to merit inclusion in a single species or possess differences warranting classification in separate species. This debate is part of a larger fissure between splitters and lumpers. Splitters magnify differences by partitioning alike individuals into different species whereas lumpers group small variations into a single species. The large number of primate species precludes discussion of all. Were such treatment possible, it would not enlighten readers because the less a species resembles humans, the less relevance it holds for understanding human diet, nutrition, and health. Regrettably, the primates most resembling us—archaic species like Homo neanderthalensis known as Neanderthals or Neandertals—are extinct. Their diets can sometimes be reconstructed but cannot be observed firsthand.
Degree of Relatedness and Definition of Species
This discussion mandates the definition of species. The most straightforward is a group of individuals that can mate to produce fertile offspring. Different dog breeds belong to one species (Canis lupus familiaris) because they yield fertile progeny. This fact justifies their designation as breeds rather than species. In contrast, crosses between a horse (Equus caballus) and donkey (Equus asinus) produce the mule, whose sterility confirms the parents as different species.
Returning to humankind, extinction limits but does not obliterate what can be known about Neanderthals. The name H. neanderthalensis differentiates them from us (Homo sapiens). The forgoing definition of species and designation of Neanderthals as separate require that they did not mate with us to produce children capable of having children of their own upon maturation. This rationale embeds assumptions about Neanderthals and us, including that they must have been sufficiently unlike modern humans to have deterred interbreeding. Putative and actual dissimilarities often convey the belief that Neanderthals were inferior to us and that inferiority doomed them to extinction. Couplings between the two must have been infrequent and seldom produced children. The few from such unions would have been oddities ostracized by their communities. Ostracism would have imperiled survival. Had they reached puberty, they could not have had children because these hybrids were sterile.
This thinking is incorrect. Studies reveal that we have Neanderthal genes. The amount varies by individual, but such variations do not negate Neanderthal ancestry, however remote those for- bearers may be. This reality implies that wherever modern humans encountered other peoples, the two mated. Accordingly, prehistoric peoples’ division into different species is likely inaccurate. Notions of separateness stem from belief that we are unique and exceptional, a comforting but inaccurate idea. This book uses conventional species names for different humans while rejecting radical notions of separateness.
The Value of Comparison between Humans and Extinct Peoples and between Humans and Apes
Returning to general considerations of relatedness, this chapter places human diets within a primate context. This context requires investigation of extinct peoples and their diets, topics of later sections. The study of human diets also benefits from examination of our closest extant relatives, the apes: chimpanzee (Pan troglodytes), bonobo (Pan paniscus), gorilla (Gorilla gorilla and G. beringei), orangutan (Pongopygmaeus, P. abelii, and P. tapanuliensis), and gibbon (species in genera Hoolock, Hylobates, Symphalangus, and Nomascus).
Early Primates and Their Diets
Viewed from an evolutionary vantage point, primates are latecomers to the biota. Life originated roughly 3.8 billion years ago, but primates are no older than 65 million years, when the dinosaurs’ demise at the end of the Cretaceous Period (145-165 million years ago) opened niches for mammals and promoted speciation. Even this date may be too early because the first species with primate characteristics may not have been primates and are probably best thought precursors rather than true to type.10 Fossils suggest that these animals resembled squirrels (Sciurus species) and tree shrews (Tupaia species). Small, the proto primates radiated heat because of a large surface to volume ratio. But being warm-blooded like all mammals, these creatures had to sustain a high metabolism to offset heat loss and so needed many nutrients and calories.
They satisfied this requirement by eating insects, a diet that supplied protein, fat, minerals, and vitamins. The visual predation hypothesis holds that primates and their immediate forebears evolved their defining characteristics to hunt insects." For example, visual acuity and dexterity enabled primates to see insects in dim light and grab them with their fingers. Insectivory (ento- mophagy) may explain the origins of humans’ preference for meat and fat. Insect capture may be classified as hunting, suggesting another parallel to people, at least before agriculture and animal husbandry replaced hunting and gathering.
Insects feed several primates, including chimpanzees, numerous monkeys, G. gorilla, lemurs (species in the superfamily Lemuroidea), and humans. Although most Westerners abhor insects as filthy and repulsive, disgust is atypical. African, Asian, Australian, New Zealand, and American indigenes practiced entomophagy. As much as 80 percent of people eat one or more of the roughly
1,500 insect species on the global buffet.12 The celebrated cave art in Altamira, Spain, suggests that its inhabitants ate insects roughly 30,000 years ago. Silkworms (Bombyx mori) fed ancient China. Colombians and Brazilians prize the leafcutter ant Atta laevigata. South Africans eat caterpillars of the moth Gonimbrasia belina. Indonesians consume grasshoppers (species in the superfamily Acridomorpha), crickets (species in the genera Gryllus, Gryllodes, Teleogryllus, and Acheta), termites (species in the infraorder Isoptera), honeybees (Apis mellifera), and sago palm weevils (Rhynchophorus ferrugineus). A 1525 account described Amerindian consumption of fleas, spiders, and worms.13 Alaska’s Nunamiut ingest maggots of the fly Hypoderma tarandi. The beetle Udonga montana is popular in India. Local markets in Thailand bulge with termites, ant eggs, honeybees, silkworms, grasshoppers, and crickets.
A type of carnivory, entomophagy, invites broader treatment of meat eating. Examining meat’s dietary roles, the next chapter critiques the assumption that it and hunting were central to our ancestors. This chapter lays the groundwork for this criticism by noting plants’ importance to many primates, including our lineage. In contrast to the visual predation hypothesis, the angio- sperm radiation hypothesis notes that primates became numerous only with the spread of angio- sperms (flowering plants).14 These plants provided fruits for primates. This perspective argues that primates, rather than being primarily insectivores, favored fruits. Corroboration comes from the fact that humans are unusual among mammals in inability to manufacture vitamin C, necessitating its consumption in fruits, vegetables, and kindred items. Our ancestors must have regularly eaten these foods, a practice that conferred no selective advantage to people whose bodies made the nutrient. Absent selective pressure, our ancestors lost the ability to synthesize it perhaps 60 million years ago.15 Over the next 30 million years, humanity’s ancestors ate primarily fruits, becoming frugivores.
Frugivory honed the brain and senses. Frugivores developed color vision to identify changes in hue that signaled ripening. These animals needed an ability to map their surroundings in the brain in order to remember locations rich in fruit trees or allied resources. They also had to sequence areas, recalling and visiting those that yielded ripe fruits in spring, after which they migrated to spots that ripened fruits later. This process, repeated over seasons and years, helped protect frugivores from lulls in food availability and hunger. In requiring concrete applications of cognition, frugivory spurred brain enlargement, an aspect of human evolution.
American anthropologist Stephen Le, mentioned elsewhere, doubted the wisdom of this diet given the dangers of excessive fructose (C6H1206) consumption.16 Chapter 2 defined fructose, noting its benefits and shortcomings. Chapter 11 treats it in the context of high fructose corn syrup (HFCS), whose derivation Chapter 2 mentioned. Criticisms against fruits, treated in Chapter 14, are part of a general wariness of plant foods. Chapters 1 and 2 mentioned that American cardiac surgeon Steven R. Gundry displayed this hostility in The Plant Paradox (2017), an approach that contradicts some nutritionists and dieticians’ advice and thereby exacerbates confusion about what to eat.
Returning to the issue of size, massiveness, like smallness, influenced what our ancestors ate. The line leading to humans and its branches—best visualized as a bush—produced species larger than the first primates. Bigness reduced the ratio of surface area to volume, metabolism, and the need to eat insects and other energy and nutrient dense edibles. Only during the last century or so has food become plentiful—perhaps too abundant—for the masses. Before then, consumption of caloric foods like animal products was the best hedge against hunger. The fact that our taste buds detect salt, fat, sweetness, and tanginess, mentioned earlier, guides the body toward calories. These preferences must have evolved to sustain humans when and where food was scarce, at least seasonally. A later section discusses famine.
As the largest primate and probably a vegetarian, Gigantopithecus, originating some 8 million year ago and now extinct, proved that enormity need not require meat consumption.17 About 3 meters (10 feet) tall and 300 kilograms (660 pounds), it likely consumed nuts and seeds given robust jaws and teeth for crushing these items. The biggest extant primate, Gorilla beringei likewise eats plants. Leaves, sterns, and shoots predominate with fruits constituting a small portion. Seldom does it consume insects. The smaller species, G. gorilla, favors plants, though it derives about 3 percent of its diet from termites, snails, and slugs.18 At least one study indicates that this species will eat monkeys.19
These creatures are branches on the primate bush, though Gigantopithecus’ twig has withered. The base of this bush regresses roughly 55 million years, w'hen the first true primates likely arose.20 This time marked the beginning of the Eocene Epoch (55-34 million years ago). Temperatures rose, producing tropical climates worldwide, conditions that favored plants and insects, both mentioned as components of primate diets. Remote eras have not yielded abundant fossils from which to infer diet. Those from Egypt’s Fayum desert suggest consumption of fruits and seeds about 34 million years ago, the boundary between the Eocene and Oligocene (34-23 million years ago) Epochs.21 Temperature reductions around this time imply diminution in number of plants and insects. Primates dependent on them may have suffered deprivation. The Oligocene witnessed the emergence of anthropoids, primates that resembled us more closely than their forebearers did and that today include monkeys, the apes, and humans.
Following the Oligocene, the Miocene Epoch (25-23 million years ago) marked the evolution of apes that ate leaves, fruits, and nuts. Gaps in the fossil record complicate attempts to pinpoint modern apes’ origins. Their diets need not be rehashed, though comparisons between chimpanzees and humans are instructive. Like humans, chimps use tools to extract food. For example, they insert twigs into logs to gather termites. Such technology resembles digging sticks, which prehistoric peoples employed to unearth roots and tubers. Chimpanzees also resemble humans in hunting game. They target some thirty-five species, red colobus monkeys (Piliocolobus species) being their favorite. Although chimpanzees may hunt alone, at other times they hunt collectively, increasing probability of success. The fact that chimps and humans share over 98 percent of deoxyribonucleic acid (DNA), discussed in Chapter 2, suggests that their common ancestor might have hunted because genes may canalize behavior and that chimpanzee hunting might prefigure early human hunting.22
