What evolution really tells us about sex, diet, and how we live
Marlene Zuk
W.W.Norton & Company, New York (USA), 2013 (2013)
328 pages, including index
ISBN: 978-0-393-08137-4

As a counterpoint to Sisson's book, I borrowed Paleofantasy from the library to take a look at a few chapters. I will just include a bunch of quotes here.

The paleofantasy is a fantasy in part because it supposes that we humans, or at least our protohuman forebears, were at some point perfectly adapted to our environments. We apply this erroneous idea of evolution producing the ideal mesh between organism and surroundings to other life-forms too, not just people. We seem to have a vague idea that long long ago, when organisms were emerging from the primordial slime, they were rough-hewn approximations of their eventual shape, like toys hastily carved from wood, or an artist's first rendition of a portrait, with holes where the eyes and mouth eventuall will be. Then, the thinking goes, the animals were subject to the forces of nature. Those in the desert got better at resisting the sun, while those in the cold evolved fur or blubber or the ability to use fire. Once those traits had appeared and spread in the population, we had not a kind of sketch, but a fully realized organism, a fait accompli, with all of the lovely details executed, the anatomical t's crossed and i's dotted.

But of course that isn't true. Although we can admire a stick insect that seems to flawlessly imitate a leafy twig in every detail, down to the marks of faux bird droppings on its wings, or a sled dog with legs that can withstand subzero temperatures because of the exquisite heat exchange between its blood vessels, both are full of compromises, jury-rigged like all other organisms. The insect has to resist disease, asd well as blend into its background; the dog must run and find food, as well as stay warm. The pigment used to form those dark specks on the insect is also useful in the insect immune system, and using it in one place means it can't be used in another. For the dog, having long legs for running can make it harder to keep the cold at bat, since more heat is lost from narrow limbs than from wider ones. These often conflicting needs mean automatic trade-offs in every system, so that each may be good enough but is rarely if ever perfect. Neither we nor any other species have ever been a seamless match with the environment. Instead, our adaptation is more like a broken zipper, with some teeth that align and others that gape apart. Except that it looks broken only to our unrealistically perfectionist eyes —eyes that themselves contain oddly looped vessels as a holdover from their past.

(Marlene Zuk: Paleofantasy, pp. 7-8)

It's common for people to talk about how we were "meant" to be, in areas ranging from diet to exercise to sex and family. Yet these notions are often flawed, making us unnecessarily wary of new foods and, in the long run, new ideas. I would not dream of denying the evolutionary heritage present in our bodies —and our minds. And it is clear that a life of sloth with a diet of junk food isn't doing us any favors. But to assume that we evolved until we reached a particular point and now are unlikely to change for thest of history, or to view ourselves as relics hampered by a self-inflicted mismatch between our environment and our genes, is to miss out on some of the most exciting new developments in evolutionary biology.

(Marlene Zuk: Paleofantasy, p. 13)

If these people are hunter-gatherers and we know our ancestors were hunter-gatherers, why can't we look at these contemporary societies and draw inferences about our earlier way of life? The answer is that we can, but to a much more limited extent than many people would like. First, contemporary hunter-gatherers are variable in what they eat, how they divide labor between men and women, the way they raise their children, and a whole host of other features of daily life. Were our ancestors more like the Aché of tropical South America, who hunt small game but also eat a variety of plant foods; or the Inuit of the Arctic, who rely on large animals like seals for much of their food? They were probably like both, at different times and in different places, but it is impossible to tell at this stage which lifestyle was more common or which features were truly universal.

(Marlene Zuk: Paleofantasy, p. 33)

On the existence of universals:

One of the many pleasures of travel to foreign lands is making connections with the locals, people who may be extremely different from us in their dress, eating habits, or religion but who often turn out to share some basic qualities —perhaps a love of children or a fear of snakes. Global conflicts over land or politics notwithstanding, people are people.

Anthropologist Donald Brown was sufficiently intrigued by this similarity around the world, noted not just by tourists but also by scholars, that he began to catalog what he called "human universals." Despite ethnographers' emphasis on cultural differences, brown claimed in his 1991 book that "nowhere in the ethnographic literature is there any description of what real people really did that is not shot through with the signs of a universal human nature." Brown was arguing against a purely cultural interpretation of what people do, suggesting instead that biology and evolution, interacting with the environment, have produced common behaviors in all human beings. Some of the universals include incest avoidance, the rough structure of language, a male-dominated political life, use of mind- or mood-altering substances, and the aforementioned fear of snakes. Brown's vision of these universals was remarkably detailed, not only about what people did but about how they felt: "Universal People... may not know how to make fire, but they know how to use it... Tools and fire do much to make them more comfortable and secure."

(Marlene Zuk: Paleofantasy, p. 42)

How, then, did the cavemen live? It is not as clear-cut as the paleo proponents would like to believe. True, we know that early humans lived as hunter-gatherers, used stone tools to butcher their prey, produced art, and had a number of other attributes. And we can learn a great deal about how selection acts on social behavior by observing our close primate relatives. But there was no single Paleo Lifestyle, any more than there is a single Modern Lifestyle. Early humans trapped or fished, relied on large game or small, or collected a large proportion of their food, depending on where in the world they lived and the time period in which they were living. At any given moment, humans were doing some things that primates had been doing for 10 million years, such as using alliances among individuals to gain social status, and some things that were relatively recent evolutionary developments, such as making stone tools that could be attached to a handle instead of simply thrown or held in the hand. Neither one is more "authentic" than the other. Whether that is of interest to the Manhattanites trying to install meat lockers in their tiny apartments is another matter.

(Marlene Zuk: Paleofantasy, p. 43)

On the rise of agriculture:

Once the human species had spread out of Africa, people probably lived as hunter-gatherers in small groups until the rise of agriculture, which anthropologists Gregory Cochran and Henry Harpending call the Big Change. No one denies that it was a major milestone, but several scientists go further and claim that it was the beginning of a downward spiral. In 1987, Jared Diamond, who later wrote such best-selling and influential books about the history of humans on Earth as Guns, Germs, and Steel, titled an article on the establishment of agriculture "The Worst Mistake in the History of the Human Race." In it he says, "With agriculture came the gross social and sexual inequality, the disease and despotism, that curse our existence." An article in the British newspaper the Telegraph about Diamond's and others' work is similarly gloomily headlined "Is Farming the Root of All Evil"?

Spencer Walls of the National Geographic Society goes even further: "Ultimately, nearly every single major disease affecting modern human populations —whether bacterial, viral, parasitic or noncommunicable— has its roots in the mistmatch between our biology and the world we have created since the advent of agriculture." And environmental writer and activist John Feeney pulls out all the stops with, "As hunter-gatherers, we blended gracefully into Earth's ecosystems. Then everything changed. Civilization is made possible by agriculture. Agriculture is unsustainable. If it weren't obvious already, you can see where this is going."

The first point to clear up before we tackle all this pessimism is one of definition. Agriculture can be informally defined as growing one's crops and domesticating or at least keeping animals, rather than simply picking up what nature provides. But anthropologists distinguish three kinds of such food production: horticulture, pastoralism, and intensive agriculture. People probably started out with horticulture, in which relatively unmodified crops are grown and cultivated with simple tools such as digging sticks. Modern-day horticultural societies include the Yanomami of South America, who combine growing manioc, taro, and some medicinal plants with foraging and hunting in the forest for the remainder of their food. Some horticulturalists today (and probably many in the past) spend part of their time as nomads, rather than living in permanent settlements. When they do form relativelt sedentary groups, those groups are small, not likely to cluster in towns or cities.

Pastoralists, who rely on domesticated herds of animals that feed on natural pasture rather than on food provided by their keepers, have probably always been less common than crop-cultivating people, though even today a few groups, such as the Saami (known also as Lapps) of Scandinavia, who herd reindeer, persist. The animals are sometimes kept in one place for a few months at a time, as when the Saami keep female reindeer in corrals for milking during the summer. Although the reindeer, like other animals kept by pastoralists, provide the bulk of the Saami people's livelihood, the Saami and other pastoralists also trade with agricultural groups for other products, like plants foods.

Intensive agriculture is more like the form of growing food most often practiced today, though it is still seen in societies we would probably classify as "traditional," such as the rice-farming cultures of Southeast Asia. Fields are more permanent than those used by the horticulturalists, who may "slash and burn" the areas they cultivate, leaving them in between growing periods, sometimes for years, to regain nutrients in the soil. In contrast, intensive agricultural societies actively manage their fields with fertilizers and use them full-time. They also use more sophisticated tools, though these may simply be animal-drawn plows, not engine-powered cultivators. Crops are raised not only for eating by those who cultivate them, but for sale, which means that people can live in larger groups, with a division of labor between those who do the growing and those who buy or trade for the produce. That division of labor in turn means that resources —food itself or the means to purchase it— are not always divided equally, and society can become stratified.

Other than providing points of discussion to anthropologists, why do these distinctions matter? They matter because it is easier to accuse Monsanto-like agribusiness of causing widespread obesity and hypertension than it is to do the same thing to a few dozen people scrabbling in the ground for tubers using pointed sticks. And small-scale agriculture may have been around a great deal longer than people think; we are only now discovering that even the manly Neandertals had grain fragments between their teeth, and that early humans ground grains into flour (...).


This is not to deny the changes that took place as agriculture —intensive or otherwise— became established. Most obviously, the human diet changed to include and eventually depend on crops such as wheat, rice, and other grains, which meant that larger populations could be supported in one place. It also meant that the relative proportions of carbohydrates and proteins in the diet shifted toward the more reliable starches, though exactly how much is uncertain. Recent evidence from Neandertals and other fossils suggests, for example, that early humans may have eaten, and even processed, grain foods much earlier than had been supposed. Nevertheless, postagricultural diets not only relied more on carbohydrates, but were far less variable than the diets of hunter-gatherers. Estimates of the number of different kinds of plants eaten by many hunter-gatherer groups range from 50 to over 100, depending on the location of the population Nowadays, in contrast, according to David Harris of the Institute of Archaeology at University College London, "a mere 30 crops account for 95% of plant-derived energy in the human food supply, over half of which is provided by maize, rice and wheat."

Why might reducing the number of foods we eat be a bad thing? Eating a varied diet is not necessarily inherently virtuous, though certain micronutrients are probably best obtained from a variety of foods. But a varied set of crops does provide a cushion against some kinds of food shortages, in a not-putting-all-your-grains-in-one-basket way. The Irish potato famine, for example, came about because a fungal disease wiped out the potato crop that the peasants of Ireland relied on for most of their caloric needs. The disease, in turn, was able to have such devastating effects because almost all the potatoes had been select to be genetically uniform, with the size, shape, and flavor that made them tasty and easy to grow. If one potato plant was susceptible, that meant they all were, and thus the entire crop could be decimated in one fell swoop. Reliance on just a few food plants makes us vulnerable to similar calamities, and it is an ongoing concern among scientists and farmers today. It is debatable, however, whether a return to a hunter-gatherer existence — even if feasible — is the best, or only, solution to this problem.

(Marlene Zuk: Paleofantasy, pp. 45-49)

Irrespective of what they are eating, intensive agriculture allows more people to be supported in a society. Having larger groups of people around, and having them be more or less sedentary, has several consequences. As Wells and many other authors have noted, one of the clearly undesirable effects of agriculture is the proliferation of new diseases, both infectious and noninfetious. Here, then, we can point to an unmitigated downside to settling down and farming: infetious diseases, those caused by pathogenic organisms such as viruses and bacteria, were able to spread because when people are in one place, their waste tends to stay put as well. For example, cholera outbreaks occur when bacteria from infected feces contaminate the water supply, which is a problem only if you keep going back to the same polluted source to wash and drink. The disease can't establish itself in a continually moving population, so hunter-gatherers would not have suffered from it. Similarly, the virus that causes measles requires a fresh set of victims to be maintained in a population, so even if a small band of humans was infected with it, the disease would eventually have died out. In more densely populated areas, however, measles and diseases like it can be perpetually recycled into newly vulnerable targets.

(Marlene Zuk: Paleofantasy, pp. 51-52)

This is not to argue that our modern lives are not sometimes, perhaps frequently, mismatched with our ancestral environment, or that we cannot use our past to inform our present. The evolutionary psychologists, amont others, have reminded us that not all human behaviors are currently adaptive. It is extremly plausible, for example, that we crave sugar and not fiber because we evolved in an environment where ripe fruit was both nutritious and in short supply. Seeking it out meant gaining calories that in turn made it more likely the seeker would have enough nutrition to survive and reproduce, passing on hir or her cravings. Nowadays, in a world full of processed sugar in everything from ketchup to Mars bars, this eagerness to consume sweest backfires, resulting in high rates of diabetes, obesity, and other woes.

Fiber is also good for us, yet we seem to lack that same enthusiasm for filling our diets with bran. Why wouldn't natural selection have instilled a drive to seek out high-fiber foods similar to the drive it instilled for sweet foods? The answer is simple: fiber was abundant in our ancestral environments, and no one had to do anything special to acquire it. People eating a diet similar to that eaten by hunter-gatherers can consume up to 100 grams of fiber per day, in contrast to the standard American inteake of less than 20 grams, just because their food is all unprocessed. No one who craved the prehistoric equivalent of broccoli or bran muffins in the Pleistocene would have been at a particular advantage over those who did not.

Being mismatched, however, is different from being stuck. Instead of asking how we can overcome our Stone Age genes, let us ask which traits have changed quickly, which slowly, and how we can tell the difference.

(Marlene Zuk: Paleofantasy, pp. 65-66)

At a more practical level, what does the evolution of lactase persistence mean for modern people who are concerned about dairy consumption? It certainly puts to rest the notion that because dairy "is not paleo," it is not an appropriate part of the human diet. One's ability to digest milk simply depends on one's genes, and those genes have changed, at least in those of us whose heritage is rooted in pastoralists. (Note, as I mentioned earlier, that milk allergy, which is an immune reaction to the proteins found in milk, is distinct from lactose intolerance; both are genetic, but they arise from completely different genes.) Of course, people choose not to consume many foods they are capable of digesting, but the story of lactase persistence is an object lesson in escape from paleofantasy.

(Marlene Zuk: Paleofantasy, p. 107)

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 human themselves, but from the fossils of mole rats, bullet-sharped rodents that live in underground colonies with elaborate tunnel systems and rely on the enlarged potate-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.

(Marlene Zuk: Paleofantasy, p. 117)

The viewpoint that our lives would be better off if we moved as people did many thousands of years ago actually contains two different ideas, one of which is virtually unarguable, while the other is rather more controversial. The unarguable part is that many human beings today are relatively inactive, and this lack of activity is terrible for our health. Research about the detrimental effects of sedentary life on our health is accumulating from many quarters. Searching online for "sedentary lifestyle health risks" yields hundredsof thousands of hits, with couch potatoes suffering higher rates of mortality from various sources, as well as exhibiting more depression, anxiety, and other mental ailments.

The problem is more complex than merely a lack of exercise —whether exercise means hunting a gazelle, digging tubers out of rocky soil, or putting in forty-five minutes on the elliptical trainer; it's that people are spending vast amounts of time sitting. According to researchers led by Neville Owen at the Cancer Prevention Research Centre in Brisbane, Australia, "too much sitting is distinct from too little exercise" (emphasis in the original). Recent studies suggest that even for people who manage to obtain the recommended amount of daily exercise each day, the deleterious effects of being sedentary can include larger waist circumference, higher blood pressure, and problems with blood sugar levels. The television appears to be a particular villain in this regard; the more time in front of the tube, the more drastic these adverse health effects were. The Australian researchers dubbed the conundrum of people who work out vigorously for a short period each day, but sit much of the remainder of the time, the "Active Couch Potato" phenomenon.

(Marlene Zuk: Paleofantasy, pp. 126-127)

Part of the curiosity about continued human evolution probably stems from our continuing need to see ourselves as different fro other animals —a form of hominin exceptionalism, as it were. It isn't necessarily related to one's stance on the origin of humanity; even those who accept that the human species has evolved may believe we are not past all that, having finished up with evolution some time ago, as if checking it off on a grandiose "to do" list. The world of iPads and organ transplants seems far removed from the "nature, red in tooth and claw" that set the stage for Darwin's ideas.

(Marlene Zuk: Paleofantasy, p. 246)

So, does culture insulate us from the environment? Partly, but by no means completely —and it may even make some of those environmental stresses, like crowd-dependent diseases, more apparent. If technology allows us to live in larger societies, the chance of spreading diseases such as tuberculosis or measles, which require a large pool of susceptible victims, increases. And those diseases are very effective agents of selection. In addition, culture itself shouldn't be discounted as somehow different from the rest of our surroundings. As Meredith Small points out, "Culture may not seem a 'natural' force, but because it is part of our environment it is just as natural as disease, weather or food resources... humans haven't really changed the rules of natural selection." What's more, culture can itself act as an agent of selection; evolution by natural selection requires organisms to have different numbers of surviving offspring, and few forces are as powerful in influencing our family size as the society in which those people live.

(Marlene Zuk: Paleofantasy, p. 250)

The suspicion that humans might not be evolving may stem from the misconception, discussed earlier, that evolution is progressing toward a goal. A related fallacy is that all of life has been aimed at the production of humans, the pinnacle of evolution. If humans are seen as an end point, then presumably there is no need for further modification, making continued human evolution a sort of gilding of the anthropological lily. Such a notion is scientifically indefensible, of course; nature has not singled out humans for special tratment, and human beings are not the most recently evolved species on the planet in any event. That last honor, if it can be viewed as such, would likely belong to a virus, a bacterium, or another micro-organism, since their short generation times allow them to evolve, almost literally, in the blink of an eye. Humans are no more of an end point to evolution than they are its most recent product.

(Marlene Zuk: Paleofantasy, p. 253)

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