The First Hunter-Gatherers
Abstract and Keywords
The nature of the term ‘hunter-gatherer’ is discussed in the context of human evolution, followed by a brief guide to the species, groups, and timings of fossil hominins. The earliest evidence for plant-based foods, from dentition and isotopic analysis, is reviewed, followed by the evidence for meat eating, including archaeological evidence of small animal protein and later scavenging, and anatomical indicators of meat eating. The uniqueness of human subsistence from that of close relatives is discussed.
If there is one thing that palaeoanthropologists understand, it is the continuum between species, genera, and all forms of life. Human beings are defined by their relationships with (and divergence from) other primates, living and historical, and primates by their relationship with other mammals, and so on. Therefore, when considering who are hunter-gatherers and then who are the first of these hunter-gatherers, palaeoanthropologists are one of the few types of archaeologist whose job is not to think immediately of Homo sapiens communities, but of creatures who are positively not Homo sapiens. It is tempting to think of hunter-gatherer behaviour as the first version of human food-getting strategy: that ‘the first hunter-gatherers’ is the same as ‘the first eaters’. If this were true then, given the unbroken continuum of the evolution of humans from primate ancestors, it would be impossible to identify the first creature to get its own food: any species that you picked out as a possible ‘first’ would itself have an ancestor. Moreover, once we get back further than hominins, archaeologists and anthropologists tend to lose interest.
However, we do not need to stretch our brains back to the primordial soup. The first hunter-gatherers are not the same as the first eaters. For one thing, it appears reasonably certain that the earliest hominins were vegetarians, with hunting coming on board much later, having gone through a stage of scavenging before hunting. We might characterize the development of human subsistence as: gathering, then scavenger-gathering, then hunter-scavenger-gathering with scavenging probably reducing in importance as hunting increased. Having said that, whether you then characterize very early vegetarian ancestors as ‘gatherers’ depends very much on the definition you use. Does ‘gatherer’ equal ‘plant eater’ (and thus include a huge range of living herbivores, frugivores, and folivores—or prey, as they are otherwise known)? Or does it imply a certain level of sociology: division of labour, planning, mapping, or sharing? How would these aspects be evidenced in the fossil record? More pragmatically, is there a physical and cognitive difference between gathering (collecting, carrying, hoarding, delayed consumption) and simply grazing as you go? If so, we exclude most non-human animals—and quite a few hominins—who eat plants from the term ‘gatherer’, yet it would be difficult to exclude carnivores such as raptors and cats from the term ‘hunter’. A question about who the first hunter was would surely involve an (p. 178) animal predator. And, humans are not the only omnivore: a significant minority of living non-human animals, including our closest relative the chimpanzee, our best friend the dog, and our usual taphonomic body double, the pig, are also omnivores.
Disentangling the non-human animals from those human ancestors is difficult simply because subsistence behaviour is a fundamentally natural, animalistic behaviour. Hunter-gathererism might be considered a human behaviour now, but it is not unique. It did not appear at the same time as hominins appeared, it did not appear as a package deal, and however culturally complex it might be today, it is derived from the need to eat, which is common to all life. This chapter goes on to examine the emergence of the component parts of hunting and gathering as a human behaviour, having noted its relationship to the subsistence behaviours of other animals.
This semantic nit-picking might be annoying, but it is necessary if we are to answer any questions regarding ‘firsts’ in human behaviour. If hunting and gathering is defined in terms of a modern human behaviour then this can only extend to Homo sapiens, and this chapter should be written about the first examples of this species, occurring in Africa at sites like Omo (Butzer 1969; McDougall et al. 2005), Blombos Cave (Grine et al. 2000, Jacobs et al. 2006), Herto (White et al. 2003), and Klasies River Mouth (Churchill et al. 1996; Rightmire and Deacon 1991; 2001) around 200–100 kya (thousand years ago), and in the Upper Palaeolithic of Europe from 40 kya (Lartet 1868; Trinkaus et al. 2003; Wild et al. 2005). There is even disagreement over which fossil should be called the earliest example of Homo sapiens, because it is not clear how far we should allow anatomical variation to be tolerated within one species. Modern humans are extremely uniform in their appearance and genetic codes, but there may have been more variability in the deep past, as there is more variability in other modern animal species.
If we are extending our interest in the history of human behaviour to ancestral hominins then we can certainly talk about the food-getting behaviour of Neanderthals. As the most recent non-sapiens hominin, we have a relative wealth of archaeological record from them, and it seems certain that they were collecting, storing, and cooking plant foods (Henry et al. 2011) as well as hunting and butchering large game (Richards and Trinkaus 2009).
We have enough evidence to at least debate the subsistence strategy of Homo erectus and possibly some transitional Homo, and to a certain extent of Australopithecus and Paranthropus. Evidence for the diets of these hominins exists archaeologically (as stuff, primarily stone tools and animal bone debris), chemically (the analysis of isotopic signatures in tooth enamel and bone), and anatomically (as skeletal form indicating function, and microscopically, as wear patterns on teeth). In some cases there is evidence for butchery sites, ‘home-base’ sites where food was brought for eating and sharing, and fire and/or cooking traces on animal bones. However, our evidence is always sparse even compared to the evidential luxuries available to archaeologies of later, much shorter periods, let alone in proportion to the time period covered. This makes this chapter largely a biological or subsistence one: readers should note that there is little scope for discussing how subsistence was culturally regarded by early hominins.
Who, When, and Where? A Potted Guide
Some context of when and who we are talking about is necessary, but this chapter is not intended to be a thorough guide to the many species that populate our lineage prior to Homo (p. 179) sapiens. Not only would this information fill whole books (great examples of which are Aiello and Dean (2002), Bilsborough (1992), and Foley and Lewin (2003)), but any account would be out of date by the time you read this. New discoveries are being announced all the time, scholars differ in how many species they accept as biological likelihoods, and, with such a tiny assemblage, a small amount of new information can change the whole picture.
Instead, this part offers a rough guide to hominins, sensu Wood and Lonergan (2008), who offer a superb guide to the names and types of hominins currently known, as well as an explanation of why there is disagreement about the number of species, and which is strongly recommended to the reader. They talk of grades of hominins; groups of species grouped together by major characteristics, which is easier (and shorter) than trying to list every species.
The earliest grade defined by Wood and Lonergan (2008) is that of possible or probable hominins, which includes two genera that are doubtful, and one which is a likely candidate for hominin-ship. The fragmentary nature of the evidence and similarity of appearance of other primate groups means that, at the time of writing, some fossils cannot be established as those of upright walking hominins. The broad dates for the very early, unlikely candidates is 5.7–7 mya (million years ago), while the probable candidate, genus Ardipithecus, dates to 5.8–4.3 mya. These fossils are all from East Africa: Chad, Kenya, and Ethiopia.
The second grade is archaic hominins, and this includes well-known as well as newly recognized species of the genus Australopithecus (referred to in lay terms as australopithecines), a genus defined by Dart (1925), plus the one known member of a recently established additional genus, Kenyanthropus (Leakey et al. 2001). This group dates 4.5–2.4 mya and represents creatures that were definitely bipedal but with relatively small bodies and brains. Some members show signs of remaining comfortable in tree environments as well as being bipeds on the ground. In this grade, Australopithecus is known from both South African and East African locales whilst the aptly named Kenyanthropus is currently known only from Kenya.
The third grade, megadont archaic hominins, includes those species who exhibit significant specialization in their dentition and masticatory anatomy (and presumably in their diets, of which more below). These species were initially categorized as Australopithecus, but most workers now use a different genus name, Paranthropus, to distinguish them, although most people agree that Paranthropus is likely to be ancestrally derived from Australopithecus. These hominins had bodies and brains almost as small as the previous group, but bigger faces and teeth, and date 2.5–1.4 mya. Again, species from both East and South African locales are recognized.
Australopithecus, Paranthropus, and Kenyanthropus are genus names, on an equivalent level with Homo. The beginnings of Homo are characterized by Wood and Lonergan (2008) first as transitional hominins, a grade containing long-established but scantily evidenced species from East Africa that may or may not be reclassified when more evidence is uncovered, dating around 2.4–1.6 mya. Following the transitional homins are pre-modern Homo, a large grade containing the famous faces of our more recent ancestry, some thoroughly well known and established such as Homo erectus and Homo neanderthalensis, and other newer ones such as Homo floresiensis. The timeline here is 1.9 mya to 28 kya. This grade is first seen in East Africa (H. ergaster: there are some South African fossils assigned to early Homo but not currently classifiable beyond that), then develops into H. erectus which later moves into Asia and Europe, giving rise to the Neanderthals in Europe (and some transitional (p. 180) forms) but keeping the classic H. erectus form in the Far East. Finally—for now—comes the grade ‘anatomically modern humans’, which contains only one species, Homo sapiens (sensu stricto) from about 200 kya onwards.
Note that the time zones overlap for most grades, and that these broad dates are judged on the fossil finds that we have. Since it is unlikely that our fossil collections contain the very first and very last member of any species or genus, we can assume that each time zone is a minimum, and the overlap was probably more extensive. The fact that for the majority of hominin history it has been the norm for several species and/or genera to be sharing resources and landscape, including Homo sapiens for the majority of its tenure, is at odds with our experience of the world, but of course has strong implications for the evolution of diet and subsistence strategy.
The sections below outline the evidence, circumstantial (i.e. anatomical) and direct (chemical or archaeological), for the development of the various components of the human diet. Each section is formatted in accordance with the history of investigation: for earlier hominins, anatomy first and direct evidence later, as the latter relies heavily on recent scientific techniques. For Homo, archaeological investigations came first, largely because there just is more archaeology available for them, and anatomical modelling came later.
Plant-Based Subsistence: Archaic Hominins (5.8–1.4 mya)
Circumstantial Evidence: Form Indicates Function
Information about the diet of very early hominins is based on fragmentary skeletal evidence which has been examined on the basis that form indicates function. Where the function is not obvious, analogies are drawn from closely related living animals, or from animals with analogous diets (e.g. Constantino et al. 2011) where we can see what something is for. It is a case of examining the fossil remains of hominin teeth and bodies and reverse-engineering their diets and behaviours from the physical adaptations made to them. As we are dealing with biological function there is little concern in the literature with the philosophical rightness of using this kind of analogy. It is well understood that analogy generates assumptions, not facts, which are often broader than we would like—but, for some small scraps of hominins, that is all we can get.
For example, when Ardipithecus was first announced in 1994, its thin tooth enamel (thin compared to that of Australopithecus) was cited as evidence for fruit adaptation. Chimpanzees (Pan troglodytes) have especially thin enamel on the occlusal (biting) surface of their incisors which is considered an adaptation to a heavy reliance on ripe fruits (Suwa et al. 2009), and so the same was applied to Ardipithecus. However, the more recent publications have argued that the enamel on Ardipthecus teeth is not as thin as in chimps, just thinner than in Australopithecus, so is not necessarily indicative of reliance on ripe fruit (or sharing special traits with Pan), but of generalized woodland plant eating (Suwa et al. 2009; White et al. 1994), reminding us to avoid relying too heavily on analogy.
(p. 181) Another example of form indicating function is in one of the best-established Australopithecus species, Au. afarensis. This hominin dates between 3 and 2 million years, and includes the famous specimen ‘Lucy’ or AL-288-1 (Johanson and Maitland 1981), a 40 per cent complete skeleton. This hominin’s teeth are indicative of generalized vegetarianism (Bilsborough 1992), with neither molars nor incisors dominating. Coupled with recent evidence that the East African landscape in which it lived was more heavily forested than originally thought, it is likely that this species was a fruit and plant eater, taking advantage of all and any plant foodstuffs without specialization. Au. afarensis was a biped but was probably also comfortable climbing trees, with mobile shoulder joints and long, curved fingers. A life spent in forested environments would be consistent with a vegetarian diet emphasizing fruit, and chimes well with research on possible home-base sites (see below). In contrast, the paranthropines (the megadont grade) show strong specialization in their reduced anterior dentition and expanded, powerful molars—indeed, the first specimen of the East African megadonts was nicknamed ‘Nutcracker Man’ (Leakey 1959; Lee-Thorp 2011). This level of dental specialization indicates a dietary specialization, unlike the generalized Au. afarensis, and investigations into this specialization have resulted in lines of direct evidence.
Direct Evidence for Plant-Based Foods
Megadont archaic hominins, or paranthropines if one prefers, are the robust-faced group comprised of the species P. robustus from South Africa, and P. boisei and (much earlier and probably ancestral) P. aethiopicus from East Africa. These hominins exhibit a markedly specialized dentition of large square molars of the crushing-grinding type seen in herbivorous chewers like sheep and horses, with very small, flat incisors. The enamel on their teeth was very thick, in contrast to Ardipithecus. Combined with this are faces that are wide and flat, small braincases, flared cheekbones accommodating very large chewing muscles, and in some cases (probably males, according to living ape analogies) a sagittal crest. The whole skull is heavy, buttressed, flattened, and strong, which looks very aggressive but probably indicates reinforcement against powerful chewing rather than fast sharp snapping of jaws. As noted above, this anatomy was initially taken to indicate the need for powerful crushing of hard-cased food items such as nuts or seeds.
Although this seems a simple case of form indicating function (Rak 1983), recent attempts to determine the hardness of the food items eaten by these creatures from scratches and striations on their teeth demonstrate how advances in scientific technique can overturn these assumptions. Using high-resolution microwear analysis, Ungar et al. (2008) showed that in seven P. boisei specimens there was no evidence, from tooth wear at least, that the individual had eaten anything especially hard in the few days prior to death. These authors posited that paranthropines had the ability to eat rock-hard seeds and tough plants when necessary, but that it was an emergency fallback ability rather than a usual choice. This is an example of Liem’s paradox, which states that very derived (specialized) adaptations do not necessarily indicate the preferred day-to-day habits of a creature, but its last resorts (Liem 1990). Therefore paranthropines may have been eating a much softer diet than has been traditionally considered, while preserving the ability to eat very hard foods in times of crisis. A special edition of American Journal of Physical Anthropology (2009) devoted to fallback foods and their importance in primate and hominin evolution highlights the increasing interest in this topic as a key force in evolutionary change.
(p. 182) Isotopic analysis by Sponheimer and Lee-Thorp (2006) on P. robustus specimens supports the idea that paranthropines were not limited to crunching tough food items, or perhaps not crunching them at all. This study indicated that the diet of these hominins was more variable than had been previously thought. The isotopic evidence from this study indicated a high level of grasses or sedges in the diet, but the authors also noted that this could have occurred not only by P. robustus eating grasses, but also from P. robustus preying on animals that ate grasses, although there is no other evidence for meat eating at this time.
This study was superseded (Cerling et al. 2011) by further investigations into the carbon isotope ratios of both P. robustus and P. boisei. Here, dental enamel samples of both species were analysed, and revealed that P. boisei was eating a diet almost entirely composed of C3 plant stuffs (grasses and sedges) with little input from C4 plants (nuts, seeds, berries, fruits), and moreover, that the very high levels of C3 could only come from a diet directly reliant on eating grasses—eating animals that ate grasses could not produce high enough levels. This means that the species formerly known as ‘Nutcracker Man’ should really be nicknamed ‘Grass-grazer Man’! In contrast, P. robustus showed a more varied diet including C3 and C4 foods.
Of interest here is the fact that the facial and dental anatomy of the two species is very similar, but they occupy different territories (P. boisei known from East Africa, P. robustus from South Africa). If we take the assumption that form indicates function then these two similar forms should be eating a similar diet, but evidently the East African group went down the route of a dietary specialism to the exclusion of other foods whilst the South African group retained a generalized vegetarian diet common to many primates in similar environments. Here we can see that whilst form = function works broadly (we can see that neither of these two were snapping carnivores) it should not be assumed that it works down to the detail of being able to distinguish between two different, equally viable, African vegetarian diets.
The Invention of Meat Eating: Pre-Modern Homo (1.9 mya–28 kya)
In hindsight, it seems that the inception of meat eating amongst hominins ought to be a big fanfare, a marked leap in human evolution. After all, most other animals are strongly specialized to either carnivory or herbivory, and changing from the primate norm of vegetarian food to a mixed diet, and the behavioural changes that must go alongside, could rightly be described as a big deal. In terms of the bodily changes that seem to go with meat eating (see below), changes are quite impressive, but of course we are viewing the effect in a very few fossilized individuals. The archaeological record shows changes coming in slowly, with meat eating creeping in as an extension of gathering behaviour at first.
Direct Evidence for Animal-Based Foods: Small Animal Protein
The classic archaic hominins, then, have been characterized as devoted vegetarians of various types. It is tempting to link the appearance of animal protein in the diet with the (p. 183) appearance of Homo as either a cause or a symptom. However, this is not strictly true: there is direct evidence that Au. africanus was eating at least a little animal protein and, given the immense time depth and archaeological paucity of this period, we might assume that which we have evidence for is only a small part of hominins’ repertoire.
Au. africanus is the South African australopithecine (2.8 mya), a small-brained, small-statured biped who was probably prey more often than predator (Brain 1981). This species has slightly smaller front teeth than Au. afarensis, but there is nothing particularly indicative or specialized about its dentition and it was assumed to be a general vegetarian primate whose diet was governed by what was available in its dry, grassy Transvaal landscape. However, modern investigations have shown that long thin slivers of animal bone found on Au. africanus sites bear the microscopic marks of termite bites (Backwell and d’Errico 2001). This might be a mystery if it were not for the analogy of chimps: the Gombe chimpanzee group were famously witnessed ‘fishing’ for termites by probing specially prepared long slim sticks into termite mounds, causing the termites to clamp their jaws onto the stick, and then pulling out the stick and eating the termites (Goodall 1986). From this analogy it seems perfectly likely that Au. africanus was at least partially insectivorous, was deliberately modifying items in order to get termites, and was probably learning and passing on this behaviour through observation of each other. The fact that Au. africanus was ingesting termite protein has been corroborated by studies of stable isotope in the tooth enamel which shows that animal protein contributed a portion of their diet (Lee-Thorp and Sponheimer 2006). Au. africanus is, then, the first hominin for whom we have evidence that animal protein was being eaten. Whether fishing for termites counts as hunting, or fishing, or gathering remains debatable.
Large Animal Protein
During the 1980s the idea that scavenging, not hunting, had been the first mode of meat eating in human ancestors became popular, although it had first been voiced by Leakey in 1967 (Blumenschine 1987). Cut marks on bones at Olduvai Gorge and Koobi Fora (Bunn 1981; Potts and Shipman 1981) were matched with Acheulian hand axes: symmetrical, uniform, teardrop-shaped tools flaked on both sides, sharp and heavy, probably for hand-held work such as butchering and smashing, rather than throwing. These hand axes are strongly associated with H. erectus, meaning that this hominin was pronounced to be eating meat taken from carcasses after a carnivore had eaten from it. However, it is hard to say that H. erectus is the first and only toolmaker or butcher: at Olduvai it is unclear whether P. boisei, H. habilis, or H. erectus is the maker of the Oldowan industry, and there is association at Olduvai of P. boisei fossils with animal bones.
An important example here is the hippopotamus butchery site at Koobi Fora, documented by Glynn Isaac (1978a) which shows that more than diet can be inferred from this type of archaeology. Here, Isaac demonstrated that 119 stone flakes associated with a hippo carcass (presumed to have died naturally) were transported from at least three kilometres away and knapped at the site (Isaac 1978a). The transport of materials in this manner is perhaps the first archaeological evidence of this extent of planning depth in relation to food.
Isaac (1971; 1978a; 1978b) developed models of landscape use by hominins who were transporting food and stone around the landscape: to butchery sites, and to notional (p. 184) home-base sites: specified areas where hominins returned repeatedly, bringing food back either to share and/or to defend it from other predators, in the case of meat. These sites were typically around streams and so would have had vegetation and perhaps shady trees. This has implications for our concept of plant-food gathering (as opposed to grazing) as well as meat eating: Isaac postulated that carrying food, saving it for later, bringing it back to a home, to a group, was a meaningful development that marked out hominin behaviour as different from other animals. He envisioned dragging carcasses back, but also discussed the issue of carrying plant foods such as berries and shoots in two hands, and suggested that non-fossilizing items such as a simple tray of bark could have been used to make this possible. He further suggested that the division of labour originated here, with females too encumbered with young to range far from the home-base (but able to carry a bark tray) and males transporting meat from the wider landscape back to the home-base to provision females and young. Notably, Isaac did not pinpoint the origin of meat eating, home-basing, or provisioning to any specific hominin, but the temporal range of his sites made P. boisei and H. erectus likely candidates.
Isaac’s work was reviewed by Rose and Marshall (1996), whose research in primatology was brought to bear on the issues Isaac had suggested were unique to humans. Their paper combined several fields of research and is worth seeking out for the bibliography alone. They refuted the division of labour idea and of defensible homesteads, but supported the idea of home-base sites generally. They agreed that transport of resources and delayed consumption were only seen amongst humans. Amongst both positive and negative respondents were Fruth and McGrew, who suggested that the assemblages of stone and bones on the ground near watercourses were not evidence of hominins living on the ground under trees, but perhaps building platforms in the trees, as chimps do, as this would form a much better protection against most carnivores if meat was indeed being brought back to the home-base. In this scenario, the archaeological debris would have dropped onto the ground as the platform disintegrated, not been originally laid there. Fruth and McGrew also provided examples of bonobos transporting fruit for several hundred metres by walking either bipedally or tripedally to free one or more front limbs for carrying, and outlined more extensive examples of food sharing in chimps, but agreed that delayed consumption had no parallel in the non-human world (Fruth and McGrew 1996). Other respondents included Bunn, who noted that local plant resources would rapidly become depleted in any scenario where hominins were staying close to one spot.
Circumstantial Evidence: Anatomy and Dentition
The advent of meat eating is supported by changes in the hominin skeleton around the time of Isaac’s butchery sites and the appearance of the Acheulian. In many ways H. ergaster, the early African version of Homo erectus dating from 1.9 mya, and H. erectus from 1.6 mya, mark a new era: the first time we have a well-established, predictable anatomy, strongly associated with a stone-tool industry which is uniform and symmetrical in manufacture, and with a much larger brain than has been seen before.
The anatomy of H. ergaster/erectus supports the advent of meat eating in several ways and is best explained by Aiello and Wheeler’s ‘expensive tissue hypothesis’ (1995, and reviewed and revised in Isler and van Schaik, 2009; Barrickman and Lin 2010; and Ruxton and (p. 185) Wilkinson 2011). This theory draws on: the large increase in brain size compared to earlier hominins; changes in body height and build; the taller, flatter, more slender and human-like torso shape; and dentition. Readers should note that the two species are somewhat conflated in this hypothesis: the real brain increase is seen in H. erectus not in H. ergaster, but what we know of the postcranial (neck down) anatomy of these two species is mostly down to the almost complete skeleton of a young male, WT-15000, from Nariokotome (Walker and Leakey 1993), described on its discovery as H. erectus (Brown et al. 1985) but following development of our understanding of these species, now classified as H. ergaster (Wood and Lonergan 2008).
Homo erectus had a brain of 900–1,000 cm3, much bigger than australopithecines and paranthropines (500–600 cm3), transitional early Homo (500–775 cm3) and H. ergaster at 760 cm3, although not as large as ours (around 1,450 cm3). The brain is a highly expensive organ to maintain in terms of energy consumed for its size, so larger brained creatures need to consume more calories than small brained ones. If a species has a larger brain than its ancestors, it must be getting more calories: either there are increased calories in the diet, or some other organ is reducing to free up extra calories for the brain. Aiello and Wheeler argued that in H. erectus we see both.
The ribcage shape of H. ergaster in WT-15000 provides evidence for the reduction of another organ to pay for the expansion of the brain. In earlier hominins such as Au. afarensis (see AL-288) and in modern apes, the ribcage is narrow at the shoulder but splayed out wide at the base, making a cone shape that results in the familiar pot-bellied torso shape of the non-human great apes. The narrow top facilitates shoulder and arm flexibility for tree swinging while the wide base houses a very long gut. This long gut is necessary because these animals (and by extension, hominins, which share the pot-belly ribcage shape such as Au. afarensis) eat material that takes a long time to process: heavy vegetation, fruit rinds, and waxy leaves that would be indigestible to modern humans with their short gut. Only by spending a long time inside the gut being processed can these plant materials be broken down into a form that can be absorbed as animal energy. What is more, the amount of calories yielded by a waxy leaf, once you have accounted for the calories expended in the long processing of it, are quite low. In a modern human, though, that leaf would be out the other end virtually intact before it had a chance to start breaking down, thus yielding no calories to the human, and costing a few in pushing it along.
Modern humans have a flat, rectangular ribcage and abdominal region, housing a shorter gut, which can be seen in those people without excess fat. In H. ergaster we see something halfway—the ribcage shape is not as flat and square as ours, but it is less cone shaped than that of earlier hominins, resembling a bell (Aiello and Wheeler 1995). So we can deduce that H. ergaster’s gut was shorter than that of its predecessors but not as short as ours. This means that the gut tissue itself, which is metabolically the second most expensive after the brain, would be reduced, freeing up extra calories for use by the brain. But what about the loss of gut length? Would this not mean a loss of calories from less processing, thus outweighing any calorific increase gained by reducing the gut length? Yes, it would—if H. ergaster was eating the same diet as the longer-gutted archaic hominins, this would mean a net reduction in calorific yield, not the net increase required for a bigger brain. The only way for a large brain as seen in H. ergaster and then the increase in brain size we see in H. erectus to combine a brain increase with small gut is to consume a diet that yields more calories in a shorter processing time: i.e. that is more easily and quickly digestible.
(p. 186) Animal muscle, or meat, is a food that fits the bill. Hominins are already made of meat and their bodies require animal energy to run. Transforming animal muscle into animal energy is a lot less hassle than transforming leaves and shoots into animal energy. Meat contains a lot more calories than vegetable matter because it is already a concentrated form of animal energy, plus, less of our own processing energy is used to digest it. (This is an oversimplification of course; meat requires extra biochemical kit to process it, and this must have evolved alongside behaviour. For example, Pfefferle et al. (2011) showed that human brains have more phosphocreatine circuit proteins—for getting energy out of meat—than do chimps, meaning that our brains can leach more energy out of the same piece of meat than chimps’ brains can, although skeletal muscle gets the same amount in both species. This is a genetically embedded specialism of our brains, which indicates selection for meat eating specifically related to the brain’s energy requirements.)
Other elements of the anatomy and archaeology of H. ergaster and H. erectus support the idea that they were adapted to eating meat. The dentition has molars and incisors in similar proportion to each other, in terms of size, as they are in modern humans, reflecting a more omnivorous diet (of course, these hominins would still have eaten a large proportion of vegetable matter in addition to meat, just as humans do today to varying degrees). The teeth are still larger overall than those of later H. sapiens but significantly smaller than australopithecines, and essentially, the human shape and format of the teeth, set in a parabolic (horseshoe shaped) arc, rather than a long rectangular palate as in archaic hominins and other apes, is recognizable in H. ergaster and H. erectus.
A well-known individual that may be evidence of the personal consequences of meat eating is the partial female skeleton KNM-ER 1808. This specimen’s femur shows thickened cortical bone consistent with Vitamin A poisoning (Walker et al. 1982). This condition, which leads to a slow and painful death, arises from eating carnivore liver, which is far too high in this vitamin to be consumed by humans (every schoolchild knows that polar bear liver is poisonous, but so is the liver of other carnivores including lion and leopard). KNM-ER 1808 lived for several weeks after consuming an overdose of Vitamin A (long enough for it to modify her bones before death) in a debilitated state, possibly indicating that she was to some extent cared for by other members of her group, although this must remain speculative. It seems that in the earliest stages of meat eating, hominins had not, quite understandably, established sufficient knowledge of what kinds of meat were not all right to eat.
Although there is no evidence directly to suggest whether the unfortunate 1808 ate from livers that had been scavenged or hunted, it is unlikely that hominins would go out to hunt lions. Therefore the balance of likelihood is that this liver was from an animal that had died by other means and H. ergaster or H. erectus had made use of the carcass. (However, while lions, as group hunters, are a very unlikely target, Tunnell (1996) reports an instance of a mob of baboons attacking a leopard—so perhaps it is not an impossible idea to suggest a carnivore may occasionally have been killed by a group of hominins.)
The origins of deliberate, organized hunting remain archaeologically unknown. H. erectus was the first species to move outside of Africa, populating south-east Europe, where it evolved into a series of transitional forms, one of which presumably became the Neanderthals, and China and Indonesia, where it established itself as H. erectus. (Again this is a very simplified account of a hotly debated issue.) The Neanderthals are demonstrably big-game hunters, but these are the first hominins for whom that can be said. It is entirely likely that earlier Homo meat eaters, scavenging large game and collecting small animals, (p. 187) would have hunted larger animals opportunely, becoming more adept and confident over time, but this sadly must remain speculation.
The Uniqueness of Human Hunter-Gathering
The Other Hunter-Gatherers
Finally, a bold statement was made above that human hunter-gathering is not unique. A reviewer of this chapter asked that the aspects that separate humans from other animals be stressed, but it turns out to be hard to find such aspects for most of the history of hominins. Although the level of technological achievement and organized big-game hunting of the Neanderthals and later humans certainly differs from any other primate’s strategy, these come in relatively late, and for the majority of the timeline of hominins, our ancestors were behaving in a fairly generalized primate fashion. Even when meat eating creeps in, it is through behaviours that have either identical (termite fishing) or strongly correlative counterparts in chimpanzee life.
Although, as noted, humans are certainly not unique in being omnivores, we cannot really term pigs or dogs hunter-gatherers: both are foragers and opportunists for the most part. However, chimpanzees may quite genuinely be termed hunter-gatherers. Isaac (1978a) highlighted the example of chimps, but claimed that taking food back to a recognized home-base to eat later, and sharing, were two behaviours that marked a difference between chimps and early Homo. However, since then several studies have observed chimps behaving in ways that undermine some of Isaac’s tenets of humanness. Chimps cooperate in running down prey and have a pecking order in terms of sharing the meat from the kill, including a preference for certain parts of the prey (Boesch and Boesch 1989). Meat may be used socially as a manipulation/reward: some workers have claimed that female chimps swap sex for meat from males (Gilby 2006; Gomes and Boesch 2009). Chimps also have a complex gathering and sharing behaviour when it comes to plant foods (Bethell et al. 2000; Slocombe and Newton-Fisher 2005). Chimps not only modify twigs to fish for termites (Goodall 1986) but have a wide range of tool-using behaviours that vary in the number and degree of their expression from group to group—i.e. there are differences in material culture signatures between groups (McGrew 1977; Whiten et al. 1999). At the time of writing, the storing of food for lean times, and food processing (cooking, combining, drying) appear the only parts of human subsistence behaviour that chimps do not do. However, there are animal homologues—plenty of other animals such as pikas and ground squirrels gather and store dry food for winter either in caches they return to (pikas) or burrows they live in (squirrels) (Hickman and Roberts 1995), while others such as bears stockpile calories as body fat; Japanese snow macaques learned to wash potatoes in saltwater to season the flavour, which may tenuously count as food preparation (Kawamura 1959; Kawai 1965); and the history of this area of research shows that the surest way to ensure that chimps are spotted doing something is to publish a paper claiming that they do not do it.
Given that chimpanzees in the wild spontaneously exhibit these behaviours it is difficult to claim that hunter-gatherer behaviour belongs only to humans, or that it defines humans. (p. 188) Chimps are modern living animals so they are not, of course, ancestral to us or ‘the first hunter-gatherers’—indeed, what we really lack is any archaeological or fossil record for chimpanzees: it would be very interesting to know whether it was Homo or Pan who were first with various aspects of hunter-gathering. It seems likely that the two strategies developed independently, one as a savannah-based strategy and the other (the Pan version) as an arboreal strategy, and this may in fact be the difference between the two.
In sum, this chapter has reviewed what we know of hunter-gathering, or its antecedents, in our ancestors and in our close relatives. These ancestors date from at least five million years ago and we have seen how meat eating develops in later stages from a default setting of primate vegetarianism and how the dentition, anatomy, and archaeology of hominins demonstrate this.
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