Changing Circumstances and Diets

Autotrophs

Typifying Rome’s enthusiasm for botany and books, lawyer and politician Marcus Tullius Cicero (106-143 BCE) remarked that “If you have a garden and a library, you have everything you need.”1 Despite this praise, few contrivances betray plants’ vulnerability more than a garden. Cabbage (Brassica oleracea var. capitata) seedlings mature in neat rows, in time filling their heads with delectable leaves. But anticipation of the harvest is premature. Within striking distance of a meal, groundhogs (Marmota топах) probe the perimeter for weaknesses, burrowing under fences. In a single evening, they devour weeks of toil. Rooted in the soil, cabbage and other treats cannot flee the assault. This shortcoming is understandable because plants need not search for food. It comes to them as sunlight, carbon dioxide, water, and minerals. Plants’ majesty stems from their status as autotrophs.

Heterotrophs

Disadvantages

In contrast, animals’ heterotrophy condemns them to seek food. Genesis, the first book in the Hebrew scriptures, conveys something of the difficulties. According to it, God banished humans from Eden, mandating that they thereafter labor for sustenance.2 Nothing comes easily to them. This book cannot match Genesis’ poetry, but, like it, this chapter aims to trace part of humanity’s prehistory and history. The task is too immense for a single volume, necessitating concentration on a single aspect of our past: diet and nutrition’s effects on health. This chapter puts this objective in an evolutionary context in hopes of illuminating how our biology and development over many millennia shaped our diet. This chapter also endeavors to indicate how foods influenced our biology and evolution. Not only have foods affected humanity, but people have modified them through a variety of interactions culminating in the rise of farming and livestock raising and subsequent genetic manipulations through selective breeding and biotechnology.

Classification of Heterotrophs

Heterotrophs may be classified by what they eat, with the range of foods determining degree of specialization. Herbivores eat only plants. This category includes specialists like the panda (Ailuropoda melanoleuca), which derives almost all its nourishment from bamboo (species in subfamily Bambusoideae) leaves, stems, and shoots. Such narrowness poses risks because the staple’s endangerment causes hunger and starvation. Eradication of that food triggers extinction. At the other end of the spectrum are herbivores that eat many species. Elephants (Elephas maximus and Loxodonta africana), for example, consume several plants’ bark, branches, roots, leaves, and fruits. Herbivores feed carnivores. Lions (Panthera leo), for example, target the African savanna’s herbivores. Not necessarily restricted to herbivores, carnivores may also eat other carnivores and omnivores. Carnivory is not unique to animals because the Venus flytrap (Dionaea muscipula) and allied plants consume insects. Such organisms are both autotroph and heterotroph.

Herbivores and carnivores’ specialization does not characterize omnivores, including humans, which differ from the others by feeding at more than one trophic level. To be sure, people may narrow their diets to one level, as do vegans mentioned in Chapter 1. Such restriction may be voluntary, though this book emphasizes that throughout history, poverty prevented commoners from affording meat. Biology does not, however, require abstinence from meat. To be sure, diseases may limit diets. Celiac disease, for example, prohibits consumption of wheat (Triticum monococcum, T. dicoccon, T. aestivum, and T. durum), rye (Secale cereale), barley (Hordeum vulgare), and triticale (Triticale hexaploide). Some with the malady cannot eat oats (Avena sativa). Yet even these cases neither prevent omnivory nor typify humanity.

Human Adaptations for Omnivory and Eclecticism

Far from excluding options, biology equips humans for a range of foods. Evolution adapted the teeth for omnivory. Molars and premolars crush and grind tough materials like seeds. Such activities help process plants as a first step in digestion. Additionally, premolars are adept at tearing meat. Incisors and canines bite and slice plants and meat. Due to the absence of enzyme cellu- lase, humans cannot digest cellulose—(C6H10O5)n, where “n” is a positive integer—in plant cell walls and so are not adapted to eating just plants. At the same time, humans do not consume only meat because it cannot satisfy cravings for sweetness, which orient the taste buds toward fruits, honey, and the sucrose (C|2H22On) conspicuous in sugarcane (Saccharum officinarum) stalks and sugar beet (Beta vulgaris spp. vulgaris) taproots. Moreover, consumption of only meat is fatal, a phenomenon known as rabbit starvation.3 Marbled meats and oily fish, nuts, seeds, fruits, and legumes demonstrate that omnivory can satiate fat cravings. In addition, humans have neither the four-chambered stomach that equips cows (Bos taurus) for herbivory nor the fleetness that enables cheetahs (Acinonyx jubatus) to outrun prey.

Rather than specializing in either of these directions, humans are generalists w'ho consume plants, fungi, fermented foods and beverages, animals, and animal products. To put the matter another way, humans specialize in eclecticism and flexibility, modifying behaviors to fit changing circumstances. Such plasticity is an evolutionary outcome and a reason why people have colonized every continent. Scientists maintain facilities even in Antarctica. Despite the norm of only one child per birth, humans number in the billions. The adaptability inherent in omnivory helps explain our success as a species.

Dietary Breadth

The Role of Choice in Dietary Breadth

Skill in manipulating crops has given people over 20,000 species of edible plants.4 Addition of animals and their products enlarges this tally. Despite omnivory and eclecticism, humans eat only a fraction of this total, with only about twenty plant species supplying nine-tenths of food.5 Detractors blame farming for reducing dietary breadth, a development examined later, though this criticism may be unfair. If Americans stopped eating hot dogs and demanded okra (Abelmoschus esculen- tus), Swiss chard (Beta vulgaris ssp. vulgaris), kale (Brassica oleracea ssp. sabellica), garden cress (Lepidium sativum), brussels sprouts (Brassica oleracea ssp. gemmifera), pinto beans (a variety of Phaseolus vulgaris), and Chinese cabbage (Brassica rapa ssp. pekinensis), farmland, restaurants, and supermarkets would change.

The Role of Preferences in Dietary Breadth

This example underscores the importance of choice in determining what people eat. Preferences shape decisions and develop early. Babies and children become unruly when forced to eat what displeases them. Earliness implies that preferences are inborn. Cravings for the salt sodium chloride (NaCl), fat, sweetness, and tanginess are widespread, again suggesting a hereditary component honed by evolution. Habits, which depend on culture, also influence choice and may cause indignation when parents raise children on processed foods.

Sodium chloride. (Photo from author.)

FIGURE 3.1 Sodium chloride. (Photo from author.)

The Role of Inequalities in Dietary Breadth

A factor that deserves scrutiny is the degree to w'hich inequalities determine what people eat. For example, introduction of potatoes (Solarium tuberosum), treated in Chapter 13, into Europe in the sixteenth century met resistance. Europeans were accustomed to eating bread, peas (Pisum sativum), lentils (Lens culinaris), cabbage, and other foods that originated in seeds. Most of their food plants produced their edibles above ground. In contrast, S. tuberosum yielded food underground, the stems, leaves, flowers, fruits, and seeds being toxic. Moreover, it was not ideally propagated by seeds in contrast to grains, lettuce (Lactuca sativa), turnips (Brassica rapa ssp. rapa), cabbage, peas, lentils, chickpeas (Cicer arietinum), and other crops familiar to Europeans. Being misshapen, the tubers were thought to cause leprosy.

These traits slowed potatoes’ integration into diets but could not vanquish necessity. Tubers thrived in the cool climate of northern Europe, where poverty drove the masses to it. Paying meager wages, industrialization left workers little alternative. In Ireland, absentee landlords extorted high rents, compelling tenants to plant almost all land to cash crops like wheat or to let livestock monopolize it as pasture. Either way, they had little land for their own needs and had to plant potatoes for maximum edible biomass per hectare. Chapter 1 and a later section emphasize that potatoes fed commoners on the eve of Ireland’s famine and examine monoculture and destitution’s consequences.

Inequality is no abstraction of distant times but remains prevalent. The affluent eat steak, duck, expensive cheeses, and other foods that have many nutrients and calories whereas developed nations’ poor grow fat on empty calories and their developing world counterparts have too little to eat. Where meat is available, as in the United States, the underclass frequents hamburger joints and greasy diners. Vitamin C comes not from whole vegetables and fruits but from French fries and potato chips. Schools perpetuate an emphasis on junk by serving tater tots and deeming ketchup a vegetable.

Government aggravates these problems. Under fortieth U.S. President Ronald Wilson Reagan (1911-2004), the U.S. Department of Agriculture (USDA) in 1981 loosened restrictions on lunch programs, allowing schools to classify pickle relish and ketchup as vegetables, cake, cookies, and corn (Zea mays) chips as bread, and cake made with eggs as meat to perpetuate an illusion of wholesomeness.6 More recently, following 2018 mandates that schools need not serve whole grains and reduce salt, the USDA in January 2020 announced its intention to allow more pizza, burgers, and fries in student lunches.7 In these ways, inequalities and the delusion that unhealthiness can be reconceptualized as vitality worsen chronic diseases.

Ronald Reagan. (Photo courtesy of Library of Congress, https://www.loc.gov/pictures/item/ 2011632924/.)

FIGURE 3.2 Ronald Reagan. (Photo courtesy of Library of Congress, https://www.loc.gov/pictures/item/ 2011632924/.)

The Role of Several Factors in Dietary Breadth

The foregoing indicates that many factors shape what people eat and their ability to acquire food in the first place. Although inequalities limit choices, modernity has made food almost effortless to obtain. A drive to the grocer or Burger King fills the stomach. But this ease is recent. For almost its entire tenure on Earth, humanity had to search for food. The quest for edible plants is known as foraging, gathering, or collecting. The term “hunting” ennobles the pursuit of game, though scavenging might have been more important throughout much of prehistory. The fact that the kidneys and liver detoxify the body implies that humans have long eaten rancid meat. Decomposition set in because humans were latecomers to a carcass. They scavenged before they hunted and continued to steal kills when opportunity arose, hunting yielded nothing, or edible plants dwindled. Chronicling this development, American anthropologist Clark Spencer Larsen (b. 1952) wrote that as scavengers, our ancestors accessed meat about 1.5 million years ago, becoming hunters about 800,000 years later.8

 
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