Most archaeofaunal materials are subsistence residues. Human nutritional requirements and animal bodies’ nutritional benefits set parameters for human’s choices in acquiring animals for food. Some background in these generally uniform properties of living human and nonhuman animals helps zooarchaeologists grasp factors that underlie the prey choice and handling evident in archaeofaunas . This chapter deals with human nutritional “constants” and how zooarchaeologists began to use some of these to understand their assemblages.
Before reviewing this nutritional data, it is worthwhile to outline major shifts in hominin diet and continental expansion in relation to the expanded carnivory of the genus Homo. Human ancestors evolved in Africa, as did anatomically modern humans, Homo sapiens. Stable carbon isotopes indicate that, from four million years ago, multiple species of African hominins shifted from the C3 diet typical of common chimpanzees (Pan troglodytes), to one emphasizing C4 plants , tropical grasses or sedges of African wetlands. This shift coincides with expansion of grassland habitat in Africa. Stable carbon isotopes cannot distinguish between the consumption of C3 and C4 plants and the eating of animals that consumed such plants. Early Homo shows more dietary diversity than some other hominin species, with a mix of C3 and C4 sources. The earliest flaked stone tools are well dated to 3.3 million years ago (Harmand et al. 2015); the earliest widely agreed upon evidence of stone tools marks on animal elements dates around 2.5 million years (Domínguez-Rodrigo et al. 2005). Claims for cut marks at nearly 3.4 million years remain controversial (McPherron et al. 2010; Domínguez-Rodrigo et al. 2012). The genus Homo is thus descended from omnivores that, from around 2.5 million, engaged increasingly in acquiring larger vertebrates for food, as evidenced by bones with cut marks and hammerstone traces at multiple sites in eastern Africa around 2.0 million years ago (Braun et al. 2010; Domínguez-Rodrigo et al. 2010). Homo erectus emerged slightly less than two million years ago in Africa, with individuals on average larger in brain and overall body size than earlier species. Some attribute these traits and the species’ successful dispersal into tropical and temperate Eurasia about 1.7 million years ago (Antón 2003), to increased input of animal foods (Klein 2009), others to using fire to prepare plant foods (Dominy et al. 2008), still others to a combination of pyrotechnology and new social arrangements among adults (Wrangham 2009). This 1.7 million year date also coincides with the estimated time of that a tapeworm of the genus Taenia that originally had a life cycle only in large African carnivores and their prey species diverged from its parent population to permanently parasitize hominins (Hoberg et al. 2001). Taenia’s life cycle depends on sustained predator-prey relationships, this suggests that, regardless of how they obtained larger animal bodies, hominins did so regularly. Homo erectus apparently adapted well to temperate climates, though their ability to live in with extreme cold situations appears not to have equaled that of later hominins such as Neandertals (Gamble 1986).
Anatomically modern humans dispersed from Africa into Eurasia, New Guinea, and Australia around 75,000 years ago (Pagani et al. 2016; Mallick et al. 2016; Malaspinas et al. 2016). Homo sapiens occupied arctic latitudes during an ice age, where animals comprised most available food, over the last 45,000 years (Fu et al. 2014; Pitulko et al. 2016). Competence living in such biomes facilitated entry into the Americas during or at the end of the Last Glacial Maximum, 25,000 to 15,000 before present. Humans’ increasing densities and more intensive interactions with certain animal species, notably the dog, in the late Pleistocene, evolved into multiple, independent animal and plant domestications in Eurasia, Africa, and the Americas in the Holocene, enabling unprecedented population growth and emergence of entirely new forms social relations.
Anatomically modern humans’ success is often ascribed to increasingly complex animal acquisition techniques and technologies such as projectile weapons, nets, and traps, as well as language and extensive, exchange -mediated social networks (Klein 2009). One could also argue that technological advances in handling plant and animal foods to facilitate storage underwrote much of human expansion, both in glacial epochs and in the later coevolution of humans and mutualist species that we call domestication . Much of this book is devoted to the signatures of different methods of handling vertebrates preserved in archaeofaunas .
5.1 Nutritional Needs Met by Animal Foods
This section outlines the contribution of each to human wellbeing, our species’ ability to store each in the body, and alternative sources of these nutrients. One can see these as uniformitarian traits of animal bodies that reward humans who incorporate them into their diets and thus as very relevant to zooarchaeological inference. Animal foods are usually high in proteins, fats (varying according to taxon), calcium, iron, and Vitamins A, B1 (thiamin), B2 (riboflavin), and C.
5.1.1 Protein
Proteins are composed of amino acids, the building blocks of tissues in the body and the precursors to antibodies, enzymes, and some hormones. Proteins also supply energy: one gram of protein supplies about 4 kcal of energy. Extreme protein deficiencies can lead to marasmus and kwashiorkor, diseases normally found only in famine conditions, or among the very poorest persons in generally low-protein-intake agricultural groups (Robson 1972).
Estimates of the amount of protein needed to maintain tissues and body function in adults vary by nation and their habitual levels of protein intake, but 50–75 gm per person per day supplies more than an adequate amount (Keene 1985:182). Severe protein deficiency in female mammals during pregnancy and lactation can produce Type 2 diabetes, hypertension (high blood pressure) and heightened risk of early stroke or heart failure in their offspring, as was discovered in longitudinal studies of children of Second World War famine victims (Barker et al. 1993; Langley-Evans et al. 1996; Godfrey et al. 1994). Effects of prenatal protein deficiency cannot be remedied by nutritional supplementation after birth. Grains and legumes supply an alternative form of protein, but these carbohydrate-rich foods do not appear to have been eaten in quantity until around the emergence of farming.
5.1.2 Fats
Fats can be derived from animal or vegetable sources. They are concentrated, relatively readily digested sources of energy, supplying about 9 kcal of energy per gram. Ingested fats are broken down in the gut, absorbed, and restructured into lipids essential to nutrient transport. They carry fat-soluble vitamins A, D, E, and K and other nutrients from the gut into the body’s circulatory system where they can be used or stored in organs or fat.
Animal fats are notoriously rich in cholesterol, which has a bad name in the popular literature because of the link proposed to atherosclerosis in modern, fat-rich lifestyles. Cholesterol is in fact an essential precursor to acetylcholine, a neurotransmitter, to Vitamin D (which is essential in bone deposition), and to various hormones, including steroids or sex hormones (Scrimshaw and Young 1976).
Disagreement exists among nutritional researchers over how much fat is needed in the human diet. Bunn and Ezzo (1993) have argued that earlier hominins’ need for fat approached that listed in the U. S. Department of Agriculture standards for fat per adult per day, thus motivating increased foraging for animal carcasses, confrontational scavenging, and finally hunting in Plio-Pleistocene times. Sept (1994) points out that the U.S.D.A. standard may be double what most humans need to remain healthy. However, extremely low-fat diets, especially if high in protein, can set into motion physiological processes leading to weight loss, illness, and even starvation, as will be seen below.
5.1.3 Essential Fatty Acids
Plant and animal fats also contain certain amino acids involved in cell membrane structure and function that are precursors to prostaglandin compounds that regulate smooth muscle and gastric function and the release of hormones (Scrimshaw and Young 1976; Garza and Butte 1986). The human body produces a range of fatty acids through its own fat metabolism, but it cannot synthesize others, without which the body cannot function and grow. These aptly named Essential Fatty Acids (EFA ) are most commonly found in vegetable fats but are also present in fatty meats.
The Essential Fatty Acids are further classified into omega-three and omega-six fatty acids, according to their chemical structure. Omega-three EFAs include alpha-linoleic acids , stearidonic acid , EPA and DHA . Alpha-linoleic and stearidonic acids are commonly found in nuts, seeds, plant oils, and green leafy vegetables, while EPA and DHA are common in oily freshwater and sea cold-water fish. Omega-six EFA include linoleic acid , highly concentrated in various nuts and in oil seeds, such as olive, canola, almond, sunflower. Omega-six EFA gamma-linolenic acid is found in some seeds, and arachidonic acid is present in meat and animal products.
Humans can store EFA in their own fatty tissues, and persons in seasonally variable ecosystems can build up a surplus when vegetable foods bearing them are common, and later tap their stored supply when they are lacking. Seasonal shortages of EFA seldom have serious effects on adults, who can mobilize the fatty acids stored in their own substantial adipose tissues (Speth 1983). However, modern medical studies indicate that infants of malnourished mothers may be especially vulnerable to effects of EFA deficiency (Innis 2007). Pregnant and lactating females mobilize cervonic and linoleic acid from their fat depots to build fetal and infant neural tissues. Deficiencies of linoleic acid can lead to skin lesions, problems with the body’s water balance, susceptibility to infection, and in immature individuals, impaired growth.
Sept (1994) argued that, under most circumstances, early hominins in tropical Africa would not have had to resort to predation or scavenging to obtain essential fatty acids and protein. These are seasonally available from plants in riparian and bush habitats in quantities sufficient to fulfill adult recommended daily allowances (RDA). Moreover, EFA from these sources could be “banked” in adipose tissues for seasonal shortfalls. Nonetheless, heightened maternal need to supply pre- and postnatal EFA to developing offspring would apply in all environments.
Modern cases demonstrate that it is possible to live on a nearly exclusively vegetarian diet, as do a number of agricultural groups in the world today (Lappé 1982). If one becomes a vegan and excludes domestic animal products such as milk products and eggs, risks include impacts of protein, vitamin B12, essential fatty acid deficiency on neural development and maintenance (Bourre 2006). Vegans depend on the present-day world food system, long-distance transport of ecologically disparate foods and smoothing of seasonality, to sustain their nutritional health. For humans in less developed and integrated economies most consumption of animal products is a simple means of fulfilling basic needs for protein, fat, and EFA .
5.1.4 Minerals
In today’s world food system, nutritionists recommend consuming dairy products, dried legumes, and green leafy vegetables as concentrated sources of calcium (Scrimshaw and Young 1976). All these foods are domesticated products, and, with the exception of the last, would have been either unavailable or available in very low quantities in pre-agricultural times. Wild green leafy vegetables would have only seasonally available. Although it has lower calcium concentrations than do these domesticated plant foods, meat constitutes a year round calcium source.
Iron is essential for production and maintenance of red blood cells, protection of other tissues, and enzymes involved in energy metabolism and is essential to fetal neurological development (Bourre 2006). Today it can be obtained from eggs, legumes, whole grains, and green leafy vegetables, as well from lean meat (Scrimshaw and Young 1976). Again, imagining times before agricultural systems, animal bodies probably were a major, year-round source of iron for much of hominin evolution, especially in temperate regions.
5.1.5 Vitamins
Vitamin A is a fat-soluble vitamin essential for the development of visual pigment and maintenance of the epithelial tissues. It plays a role in synthesis of mucopolysaccharides, a constituent in cartilage and other tissues. Beta-carotene, or Provitamin A, is a Vitamin A precursor found in green vegetables, which can be converted into Vitamin A by the body (Scrimshaw and Young 1976). Vitamin A in its complete form exists in animal foods and is richest in milk products. It can be stored in body fat. In pre-agricultural times, when vegetable sources were probably strongly seasonal and dairy sources unavailable, meat and fat would have been a consistent source of Vitamin A throughout the year. Humans can overdose on Vitamin A if they consume the liver of a top carnivore, which concentrates the vitamin. Hypervitaminosis A causes skin disruptions, anorexia, vomiting, and inflammation of bones ’ periosteum , with concomitant rapid woven bone growth around shafts, and death.
Vitamin B1, or thiamin, is a water-soluble compound, involved as a co-enzyme (thiamin pyrophosphate) in metabolism of amino acids of both plant and animal origins (Keene 1985; Scrimshaw and Young 1976). Thiamin is essential to the efficient mobilization of energy from fats and carbohydrates. Its deficiency causes beriberi, a syndrome involving nerve damage, edema, and heart failure. Because thiamin is widely distributed among plant and animal foods, meat does not comprise a special source, except in zones with extreme winters, when plant food are absent.
Vitamin B2, or riboflavin, is another water-soluble vitamin common in plant and animal tissues. It also is involved in the formation of two flavinoid coenzymes that facilitate efficient metabolism (Scrimshaw and Young 1976). Deficiencies can cause lesions in epithelial tissues of the skin and eyes. Prior to the emergence of domestic plant species and the modern world food system, animal foods assured year-round access to riboflavin.
Vitamin C, or ascorbic acid, is most abundant in plant foods such as citrus fruits, peppers, tomatoes, and greens, but it is present in meat. By maintaining the intercellular matrix, ascorbic acid is essential in the maintenance of bone, dentine , and cartilage. It is a key constituent in collagen synthesis. Scurvy, the ascorbic acid deficiency disease, involves degeneration of skin, blood vessels, and gum tissues supporting teeth .
5.2 Demands Above the Norm: Gestation, Lactation, Early Childhood
Published nutrition standards are usually based on adult and, at least formerly, male physiological needs. However, reproducing females and their offspring undergo intense, nutritionally based selective pressures hidden by adult average data. Scrimshaw and Young (1976: 56) note that investigators have tended to regard infants and young children as little adults and, with a small allowance for their growth, to extrapolate their requirements proportionately by weight from studies of older individuals. This approach does not take into account changes in the metabolic activities of cells and in the rates of turnover with age (Garza and Butte 1986).
Nutrient demands of developing mammals, and, by extension, on the supplier of their nutrient needs, the pregnant and lactating mother, differ from those of adults. Most brain growth, development of other neural tissues, and much skeletal and muscular growth occurs either during lactation or in the post-weaning phase of early childhood. It is important to recall that in most traditional pre-agricultural and agricultural societies, mother’s milk supplies nearly all a child’s nutrition for the first 2–4 years of its life (Dettwyler 2004:717–719).
5.2.1 Calcium
Prenatal maternal nutrition affects an infant’s later growth and health status. A mother’s body can supply adequate levels of calcium and lipids by mobilizing bone mineral and fats stored in her body. As noted in Chap. 4, through hormonally mediated mechanisms, pregnant females may increase absorption rates of dietary calcium to replace the mineral being mobilized to build fetal tissues. In case of severe dietary shortages, calcium continues to be mobilized from maternal bone, to the detriment of the mother’s long-term calcium budget (Fedigan 1997).
Lactation imposes even greater demands for calcium on the nursing mother than pregnancy because much skeletal growth takes place during this span. Laboratory studies of rats have shown that as much as 25% of calcium can be mobilized from thigh bones of rats during the normal lactation span. In human females, primary losses of bone occur in the trabecular areas of long bones , as they do in lactating laboratory animals (Fedigan 1997).
5.2.2 Childhood, Protein, and Essential Fatty Acids
Protein requirements from in the first year of life are more than twice that of an infant over 1 year of age, and over four times that of a young adult and (Scrimshaw and Young 1976:54). Human brain growth patterns convey a sense of the nutritional demands upon human females during lactation: at birth, a human infant’s brain is about 25% of adult size; over the first 6 months of life, its brain doubles in size. Children achieve all but 10% of their brain growth by age five and all but 5% by age ten (Tanner 1990:104). During brain growth, children require constant and relatively high levels of proteins, cholesterols and related lipid substances, and EFA , especially linoleic acid. In societies without milk animals, all but 10% of brain growth takes place before weaning, when breastmilk supplies nearly all of these requirements. Nursing infants and very young children therefore exert a tremendous demand on the maternal body. These facts are recognized in nutritional tables for pregnant or lactating human females (see Scrimshaw and Young 1976: 60–61 for adaptation of FAO tables).
A human infant’s nutritional dependency on mother’s milk is much longer than in most mammals, requiring several years of good-quality maternal nourishment, or storage reserves. Human milk is not a “high-energy, high-quality” food source in comparison to milk of many other mammals. It is low in energy per unit volume and low in milk solids, resulting in slow growth and development rates compared to those of many placental mammals (Garza and Butte 1986; Oftedal 1984; Stini 1980). Davis et al. (1993) demonstrated that human, common chimpanzee, and gorilla milk share the same protein make-up, reflecting a long evolutionary history . Mothers can slightly increase the proportions of proteins and fats in their milk, as well as the volume and calorie levels, by maintaining their own intake of high quality foods.
The key to female reproductive success is thus not simply meeting average daily individual requirements but storing and mobilizing EFAs and other proteins for their maximum, sex-specific needs of supporting infant growth and development , in the face of variations in seasonal resource availability. This is especially true in areas with shortened plant growing seasons, where animal foods may be more important sources of such nutrients. Zooarchaeologists therefore need to consider how these demands may structure foragers’ decisions in acquiring animal foods that supply many of the exceptional nutritional needs of pregnancy and lactation, without which the species cannot survive.
5.3 Coping with Seasonality
All members of the genus Homo entering temperate and colder zones faced novel dietary challenges. Some solutions were inherent to the physiology of their taxon. Even in tropical latitudes, foragers and subsistence farmers diverge from the “steady state” of food-intake that prosperous populations in the contemporary world food system take for granted. Because certain plant and animal foods are available only at given times of the year, they eat in a more seasonal pattern, with variations in caloric intake as well as specific foods (Lee 1979; Peters et al. 1981; Sept 1990). In times of food shortfall, people live off fat stored in times of abundance, breaking down fat to access calories and fat-soluble vitamins and minerals. Thus, genus Homo entered temperate zones with a physiology that permitted it to survive times of low food intake. Yet seasonality in temperate, subarctic, and arctic zones poses much greater challenges. During long seasons of frost, edible plants stop growing altogether, calling for further coping tactics, either somatic or extrasomatic.
Among vertebrates, several options have evolved to cope with overwintering through the non-growing season. Some insects , many birds, and some mammals migrate to warmer zones, a strategy that imposes its own energetic costs and dangers. Migration also removes prey biomass from the reach of carnivores remaining in the cold zone. Another strategy involves dropping into torpor – hibernating – through part of the winter. As with migration, this represents major physiological challenges and requires a resting place inaccessible to predators that could attack during torpor. Fishes, amphibians, and reptiles cope with freezing conditions physiologically, tolerating deep chilling of their tissues. Hibernating bats, bears, certain rodents, and other placental mammals drop their metabolic rates and live off stored fat, which requires accumulating enough body fat not only to survive the winter in torpor but also to forage in spring. Female bears sustain the added energetic costs of birth and lactation while hibernating. Only a few high-latitude terrestrial mammal species (Lefèvre 1997) build up enough fat to hibernate, but all must lay down a seasonal fat deposit. Deer and most other hoofed animals, many rodents, various cat species, mustelids, and raccoons accumulate deposits of fat in the summer and autumn and use it to stay warm and actively forage during the winter.
As with other animals, humans must cope with higher latitude challenges well enough to rear offspring to adulthood. Humans readily build up extra adipose tissues, and populations living in strongly seasonal regions appear especially inclined to add fat (Pond 1997). For much of human history , seasonal fattening followed by weight loss in “lean times” was normal among foragers, pastoralists, and farmers, especially those in agriculturally marginal environments. The body is the most efficient place to store food reserves: no one can steal it, and animal pests can’t spoil it. In cold climates it insulates and is a ready source of metabolic fuel. As noted above, fat stores vitamins A, C, E, and K and EFA when these are abundant, tapped when diet does not supply levels essential to body function. In a significant number of people in high-latitude populations, shortening day length provokes a lowering of metabolic rate and mood, called seasonal affective disorder (SAD), one symptom of which is craving for carbohydrates and weight gain (Rosenthal 1998). Today, SAD is viewed as a public health problem, given its risks of depression and even suicide. However, it may reflect an older adaptation to seasonal food shortage. Anatomically modern humans combine such somatic adaptations with technologically mediated food storage and long-distance exchange relations to avoid the worst risks of seasonal food scarcity, especially for infants and children.
5.4 Problems of Meat-Rich, Carbohydrate-Poor Diets in Humans
Humans are basically omnivores with some leaning toward carnivory . Truly carnivorous mammals’ physiologies build and maintain their bodies and those of their offspring by eating other animals. However, humans cannot live for long exclusively on lean meat, which without carbohydrates produces deleterious physiological reactions. In recent times carbohydrate-poor diet was mainly a risk for higher-latitude groups undergoing long cold seasons, with few storable plant foods available during summer. However, during Pleistocene glacial cycles, roughly similar temperatures would have affected groups in what are now the temperate latitudes of Eurasia and the Americas. In a landmark paper, Speth and Spielmann brought together knowledge of human physiological needs, ethnography, and zooarchaeology to explore motivations for prey species and body-segment selectivity among such groups, as well as other, technological and socially mediated tactics for coping with this problem.
5.4.1 Specific Dynamic Action (SDA) Effects
Using data from metabolic studies of humans and other mammals, historic records, and ethnographic information, Speth and Spielmann outline the energetic and physiological costs of relying very heavily on animal foods. Breaking down any ingested tissue during digestion requires energy expenditure, and protein is the most energetically expensive. Amino acids from lean meat must be broken down into glucose and other by-products via the citric acid cycle (Scrimshaw and Young 1976), and the glucose must then be converted to adenosine triphosphate (ATP) in the tissues, another energetically expensive process. The specific dynamic action (SDA ) statistic calibrates these trade-offs , expressing, as a percent, a food item’s energetic costs (see references in Speth and Spielmann 1983:5). A largely carbohydrate intake has an SDA of about 6%, that is, for each 100 calories carbohydrate ingested, 6 calories of these will be spent breaking it down. Fat SDA runs 6–14%, whereas for a predominantly protein diet, the SDA runs as high as 30%. Speth and Spielmann (1983:6) cite studies of Inuit who ingested traditional meat- and fat-rich diets, plus self-administered experiments by Arctic explorers of European ancestry, indicating that, with such diets, a person’s basal metabolic rate (BMR) increases 13–33%. The leaner the meat ingested, the higher the SDA effect because no fat offsets protein SDA.
The consequence of such a raised BMR is the need to consume even more calories to meet BMR and activity-based energy needs. The cycle continues if subsequent calories are also lean meat. This may account for explorers’ accounts of North American Plains Indians and Inuit consuming kilograms of meat at a sitting. Speth and Spielmann quote Shepard as estimating that an active Inuit male might need to consume 3600 calories in a 24-h period, and if these calories were from lean meat, between 3.4 and 3.6 kg would have to be eaten. A shift in diet toward more carbohydrates lowers BMR levels, as demonstrated by Arctic explorer research (Speth and Spielmann 1983:6).
Speth and Spielmann argue that terrestrial ungulates in temperate to Arctic zones become fat-depleted in the late winter and early spring months, having exhausted their adipose reserves while surviving on sparse forage. People eating such lean animals risk having to increase their overall calorie intake just to break even, in a season when their own bodies were also fat-depleted.
5.4.2 Effects on Body Tissues and Protein-Sparing Effects of Carbohydrates and Fats
The untoward effects of a lean meat diet do not stop with raised BMR. With such a dietary regime, the body’s physiological priorities put its own protein-based tissues at risk. Under-supply of amino acids, and hence glucose, from food will cause the body to attack its own muscle and organ tissues to produce energy. Dietary carbohydrates and fats intervene in this destructive cycle, with glucose production redirected to the carbohydrates and fats. Carbohydrates have been established as more efficacious than fats, per unit calorie administered, in reducing the breakdown of the body’s own proteins for energy.
5.4.3 Other Effects of Dietary Fat Shortage and High Protein Intake
A high-protein, low-fat diet inhibits absorption of calcium, perhaps because fat-soluble Vitamin D is not present to transport calcium across cell. Inhibition of calcium uptake during seasonal fat shortages could lead to bone loss or retarded bone deposition. These problems would be especially acute for infants and children in the process of skeletal growth, nursing mothers mobilizing calcium for milk, and post-menopausal women with calcium budgets already unbalanced by the hormonal changes.
5.4.4 Tactics to Cope with Seasonally Lean Meats
Speth and Spielmann (1983:19) contend that seasonal, fat-to-lean animal intake in environments with scarce carbohydrates may drive “lean season” hunting toward prey with high fat, rather than caloric, returns. Beavers, waterfowl, and some fishes are fat-rich, offering the fat needed to supplement lean meats from hoofed mammals.
Another strategy known from ethnographic cases is storing fat- and carbohydrate-rich foods for consumption with lean meats during the seasonal minimum. Rendering body fat from mammals, birds, and fishes, simmering bones to extract bone grease, and drying oily fish all produce storable fatty foods for winter and early spring consumption. Pemmican, the legendary traveler’s food among Plains Indians, is a compound of dried lean meat, rendered fat, and dried berries. It brings together the ingredients essential to sustaining health.
Finally, ethnographic and historic records testify to trade for fat- or carbohydrate-rich foods, as was the case in Plains-Pueblo trading relations, where bison hunters obtained maize and other agricultural produce in exchange for meat and hides. Inland and coastal Athabascan Indians in the Northwest of the U. S. and Canada exchanged furs from inland animals for rendered oil of seals, whales, or of the smelt-like eulachon fish (Thaleichthys pacificus).
5.5 Body Segments and Nutrition: Not All Parts Are Equal
Skeletal elements simultaneously play protective, biomechanical, and nutrient reservoir roles in living animals, with different elements playing disparate roles in the body. As a result, these are differentially attractive to animal consumers and are variably durable under consumption. Some bones are reservoirs of nutrients such as red marrow and yellow marrow . Others, such as the skull and vertebrae, enclose appetizing neural tissues. Any consumer able to breach bony structures to access their contents will target those elements.
At the same time, because they have distinct biomechanical functions, different skeletal elements possess variable densities of bone tissue per unit of volume, or bone mineral density (BMD ), which affect an element’s response to the impacts of consumers. Some elements, or segments of them, give way, while others do not. Thus, the uniform qualities of bones related to their life functions determine how carnivores , including humans, attack them and how the bones respond. For example, carnivores , regardless of whether canid, felid, or hyenid consume large prey carcasses in a remarkably uniform sequence of anatomical zones. This consumption sequence , discussed in more detail in Chap. 12, represents carnivores ’ trade-off between prioritizing the nutrient -richest segments and their ability to access those nutrients, given the variable resistance of the skeleton.
In Nunamiut Ethnoarchaeology (1978) and in Bones: Ancient Men and Modern Myths (1981), Binford attempted to standardize previously intuitive assessments of the relative food values of different sections of mammal carcasses. He ranked skeletal elements in order of their associated soft tissue “utility” to humans, using four different scales: meat, marrow , bone grease utilities, and then a combined general utility index . Binford ’s goal was to establish uniformitarian principles for assessing the “logic” of larger animal butchery , as well as of body segment discard or transport by hunters and to apply this approach for analyzing archaeofaunas . Binford ‘s approach can be condensed as follows: the presence or absence of bone elements with specific associated nutritional values in an archaeological site reflects their deliberate selection or abandonment by ancient hunters. Frequencies of elements of different nutritional utilities in turn allow us to assess the nature of the site, for example, a kill/butchery locale versus a residential site. Efforts to build uniformitarian frameworks for evaluating frequencies of elements will be detailed in Chaps. 20 and 21.