Paleofantasy: What Evolution Really Tells Us about Sex, Diet, and How We Live (15 page)

The results? The paleo diet came in dead last, at rank 20. “Experts took issue with the diet on every measure. Regardless of the goal—weight loss, heart health, or finding a diet that’s easy to follow—most experts concluded that it would be better for dieters to look elsewhere. ‘A true Paleo diet might be a great option: very lean, pure meats, lots of wild plants,’ said one expert—quickly adding, however, that duplicating such a regimen in modern times would be difficult.”
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Modern foods, as I detail later in this chapter, are often much higher in fat and sugar than their wild counterparts—a difficulty acknowledged by at least some of the paleo enthusiasts.

A few studies have attempted to examine the effects of switching to a paleo diet on various health measures, including weight, of groups of subjects. Unfortunately, as with all diets, doing a carefully controlled examination of the paleo diet is difficult. One such attempt took twenty healthy volunteers and measured variables such as body weight, waist circumference, cholesterol levels, and blood glucose before and after the three weeks of the study.
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Only fourteen of the subjects managed to complete the entire three weeks, and they lost an average of 5 pounds, with a 0.2 decrease in waist circumference (they were not overweight to begin with). Blood calcium levels fell by more than 50 percent—not surprising, since the subjects were not allowed to eat dairy and received no special instructions on how to obtain specific nutrients from the foods they were allowed.

The National Health Service of the United Kingdom analyzed the study, which was widely reported as confirming the health benefits of paleo eating, and was not impressed.
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It pointed to the absence of a control group—a comparison group eating in a different way, to which the participants could be compared—making it difficult to interpret the findings. The NHS also noted that a dropout rate of 30 percent suggested that the diet might be difficult to follow for most people, which means that regardless of its virtues, a paleo diet might not be a panacea for the diseases of civilization.

The hunter-gatherer table—or, mole rats and starch

Cartoon images of early hunters living exclusively off the flesh of mammoths notwithstanding, Voegtlin’s bold declaration that our ancestors consumed exclusively meat turns out to be untrue. Studies of fossil hominins suggest that their sturdy premolar teeth may have been used either to open seeds or to chew starchy underground tubers and bulbs. One rather unusual clue about ancestral diets comes not from fossil humans themselves, but from the fossils of mole rats, bullet-shaped rodents that live in underground colonies with elaborate tunnel systems and rely on the enlarged potato-like roots of wild plants for both food and water.

A mole rat away from tubers is a sad and hungry mole rat, so when groups of mole rat fossils are discovered, it means that these underground food sources must have been nearby. And indeed, mole rat fossils occur at the same sites as hominin remains much more often than would be expected by chance, suggesting that early humans also used these roots and other starchy foods. They may have used them mostly as “fallback foods” in times of scarcity, but even so, such foods would have allowed early humans to survive periods when hunting was simply not an option.

Finding out that early humans ate starchy foods is one piece of the puzzle. The other source of information about what our forebears’ diet might have been like is the diet of people now living the way we think our ancestors did, as foragers and hunters. As I mentioned in Chapter 2, there are many caveats to using modern hunter-gatherers as surrogates for early humans, but keeping those in mind, we can learn, for example, that the different cultures using foods they catch and glean eat a huge variety of different things, both plant and animal. It should come as no surprise that this variety is tightly linked to the range of climates and environments in which humans live; more northern peoples eat more meat and less plant material, while coastal cultures eat fish.

Anthropologist Frank Marlowe painstakingly examined the eating patterns and environments of 478 groups of humans across the planet, from the southern tip of South America to northern Alaska, and from eastern Australia to Africa.
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He points out that whether you rely primarily on plant as opposed to animal foods depends on where in the world you live; Old World foragers get more of their diet from gathering and less from hunting and fishing, with the converse true for those in the New World. Even among the latter, however, nearly a third of the diet comes from plants, putting to rest the notion of our carnivorous ancestors. Climate matters as well, with those living in warmer parts of the world closer to the equator obtaining a larger fraction of their food via gathering, as would be expected, given the difficulty of acquiring fruits or other plant products in a harsh climate.

One of the most interesting distinctions in Marlowe’s survey is between cultures that use bows and arrows for hunting and those that do not. Bows enable the killing of animals at a much greater distance than do spears, as well as the bringing down of larger game. As a result, it is possible to increase meat consumption, which Marlowe speculates could have spurred the growth in the human population after bows had become established in early societies. He further notes that if we are to use modern hunter-gatherers as models for the earliest of humans, we should probably stick to those groups that lack the bow, because they are the most similar to our ancestors, which leaves us with indigenous Australians and Tasmanians. Bow use is a deceptively simple advance with the potential to substantially alter the food base of a society, and it is yet another example of a subtle way in which preagricultural humans varied from a uniform hunter-gatherer model.

Another implication of the importance that Marlowe attaches to bow hunting is that, rather than starting out as exclusively carnivorous and then adding starches and other plant material to the diet, ancient humans would have been able to increase the proportion of meat only after newer technology had come about, a mere 30,000 years ago. Other anthropologists concur that the amount of meat in the human diet grew as we diverged from our other primate ancestors. All of this means that, first, contrary to the claims of many paleo-diet proponents, the earliest humans did not have an exclusively meat-based diet that we are best adapted to eat; and second, our ancestors’ diets clearly changed dramatically and repeatedly over the last tens, not to mention hundreds, of thousands of years, even before the advent of agriculture.

What people eat is also inextricably entwined with how people spend their time, and in particular with how men and women might differ in this regard. I discuss paleofantasy gender roles in Chapter 7, but it is worth mentioning that the relative amount of the food budget supplied by men versus women, related to the reliance on hunting versus gathering, is another attribute that varies across cultures. Also tied to the appearance of bow hunting was the ability of men to provide a larger proportion of a family’s caloric intake, since they were killing larger animals. Marlowe speculates that before this technological development, men might have been contributing different non-meat-based foods, such as honey, with women providing the bulk of the food eaten by the group, as was the case for the indigenous Australians in his sample.

Katherine Milton is a primatologist and anthropologist at UC Berkeley who has studied and written extensively about the diets of modern apes and monkeys, as well as those of hunter-gatherers and ancient humans. She points out that “it is difficult to comment on ‘the best diet’ for modern humans because there have been and are so many different yet successful diets in our species.”
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Furthermore, “Because some hunter-gatherer societies obtained most of their dietary energy from wild animal fat and protein does not imply that this is the ideal diet for modern humans, nor does it imply that modern humans have genetic adaptations to such diets.”
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Milton also takes issue with the attempt by paleo-diet experts to calculate the ratios of nutrients such as protein or saturated fat in hunter-gatherer diets so that these can be emulated by followers of the paleo way of life, again citing the vast range of diets eaten by modern foragers and the lack of detailed information on foods eaten by early humans.

Even if we did know more about what our ancestors really ate, Milton argues that it wouldn’t necessarily help, because those ancestors do not seem to have been particularly specially adapted to their foods, or as she says, “regardless of what Paleolithic hunter-gatherer societies were eating, there is little evidence to suggest that human nutritional requirements or human digestive physiology were significantly affected by such diets at
any
point in human evolution.”
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The notion that humans got to a point in evolutionary history when their bodies were somehow in sync with the environment, and that sometime later we went astray from those roots—whether because of the advent of agriculture, the invention of the bow and arrow, or the availability of the hamburger—reflects a misunderstanding of evolution. What we are able to eat and thrive on depends on our more than 30 million years of history as primates, not on a single arbitrarily more recent moment in time.

Milton hastens to point out, and I wholeheartedly concur, that this does not mean that many of the diseases of civilization are unrelated to diet, or that we should go further back and emulate the diets of gorillas or other modern apes rather than hunter-gatherers. If the proponents of paleo diets were correct, however, those hunter-gatherers with higher levels of protein in their diets should be less likely to suffer from modern maladies like obesity and hypertension than do cultures consuming more plants and starches, but no evidence exists to support such a claim. Such diseases are indeed absent in most foraging societies, but they are more uniformly absent than would be expected if a high meat intake were the preventive. The biggest problem with many Western diets seems to be their energy density—the vast number of calories contained in a Big Mac as opposed to an equal volume of wild fruits or game. The concentration of calories makes it far too easy to overconsume, even when it feels as if the amount of food eaten is not particularly large.

The relative proportion of carbohydrates in the diet does affect one aspect of our health: our teeth. But here the problem arose not with a switch to agriculture, but much later, when the Industrial Revolution led to increased consumption of refined sugars and processed foods. A 2012 conference at the National Evolutionary Synthesis Center in North Carolina examined the dental health of modern humans compared with that of either modern peoples eating more traditional diets, such as the Maya of Mexico, or our fossilized ancestors. People in industrialized societies not only have far more cavities than either of the other two groups—Australian aboriginals from the 1940s were described as having “beautiful teeth”—but their jaws are shaped differently, with malocclusion and overcrowding of the teeth.
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Ancient people and those consuming more fibrous foods simply chew more, which changes the development of the jawbones and associated musculature.

The scientists who studied early dental health are quick to caution against a quick fix of a paleo diet for those seeking to avoid the dentist and orthodontist; Peter Ungar from the University of Arkansas echoes anthropologists in saying, “There was not a single oral environment to which our teeth and jaws evolved—there is no single caveman diet. Still, we need to acknowledge that our ancestors did not have their teeth bathed in milkshake.”
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One potato, new potato

Even if we wanted to eat a more paleo-like diet, could we? Virtually all of the foods available to those of us not living foraging lifestyles are vastly different from the forms that our Paleolithic ancestors would have eaten. I am not talking about ice cream or Pop-Tarts, or even flour, but about the unprepared basics: meats, fruits, and vegetables.

Many of the paleo-diet fans promote eating wild game, or at least very lean cuts of meat—a reasonable recommendation, given the differences in the fat content of domesticated animals compared to their wild counterparts. For example, according to the Department of Animal Science at Texas A&M University, a 4-ounce serving of white-tailed deer meat has 2.2 grams of fat, while a similar-sized portion of extra-lean ground beef has 18.5 grams of fat.
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Game birds such as pheasant or quail have about half the calories of commercially available beef and pork. Domesticated animals that are used for food have been selectively bred, of course, to grow quickly, resist disease, and be amenable to living in much larger groups than their wild ancestors would have tolerated—all qualities that may or may not be compatible with a goal of maximal human nutrition. This is not to suggest that modern meat is unhealthy per se, but merely that eating like a caveman is going to involve more than skipping everything except the butcher counter at the supermarket.

The produce aisle has its problems too. Virtually all commonly eaten fruits and vegetables are also the result of much selective breeding by generations of farmers, whether one is growing one’s own or shopping at the supermarket, using heirloom varieties or not. The ancestral potato, for example, was a bitter, lumpy root a fraction of the size of the average Idaho baker. The wild progenitor of apples, recently traced to Kazakhstan in Central Asia, was described by Michael Pollan as “a mushy Brazil nut sheathed in leather” that would “veer off into a bitterness so profound that it makes the stomach rise even in recollection.”
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What we now know as corn started out about 9,000 years ago as a Mexican grass called teosinte, with a shape and size more reminiscent of a stalk of rice than of the fat yellow kernels on a cob. Several researchers who followed wild monkeys or apes and attempted to eat the same fruits and other plants that those animals eat reported similar off-putting results.