Paleofantasy: What Evolution Really Tells Us about Sex, Diet, and How We Live (7 page)

Farming sickness

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 noninfectious. Here, then, we can point to an unmitigated downside to settling down and farming: infectious 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.

Farming usually also means domesticating animals, and those animals can harbor diseases of their own, many of which are unwittingly passed to their caretakers. Worms, fungi, bacteria, viruses—our pets and work animals can be infected with all of them, and all have been implicated in human diseases as well. Smallpox, influenza, and diphtheria are all thought to have originated in nonhuman animals. Although wild animals can be a source of disease for hunters, the risk is much lower simply because the animals are not in contact with humans for very long.

Noninfectious diseases that would have appeared in newly agricultural human societies include vitamin deficiency diseases such as pellagra or scurvy, simply because agriculturalists tend to have fewer kinds of food in their diet, as I mentioned earlier, and the chance of relying on one or a few foods that lack essential nutrients is high. The skeletons of ancient farmers are filled with evidence of tooth decay, iron deficiency anemia, and other disorders. Diamond notes that the Greek and Turkish skeletons from preagricultural sites averaged 5 feet 9 inches in height for men and 5 feet 5 inches for women, but after farming became established, people were much shorter—just 5 feet 3 inches and 5 feet, respectively, by about 5,000 years ago, probably because they were suffering from malnutrition. The teeth from skeletons of Egyptians who died 12,000 years ago, about 1,000 years after their people had shifted from foraging to farming, were rife with signs of malnutrition in the enamel: a whopping 70 percent of them, up from 40 percent before agriculture became widespread.
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Then a funny thing happened on the way from the preagricultural Mediterranean to the giant farms of today: people, at least some of them, got healthier, presumably as we adapted to the new way of life and food became more evenly distributed. The collection of skeletons from Egypt also shows that by 4,000 years ago, height had returned to its preagricultural levels, and only 20 percent of the population had telltale signs of poor nutrition in their teeth. Those trying to make the point that agriculture is bad for our bodies generally use skeletal material from immediately after the shift to farming as evidence, but a more long-term view is starting to tell a different story. For example, Timothy Gage of the State University of New York at Albany examined long-term mortality records from around the world, along with the likeliest causes of death, and concluded that life span did not decrease, nor did many diseases increase, after agriculture. Some illnesses doubtless grew worse after humans settled down, but life has had its “nasty, brutish, and short” phases at many points throughout history.
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A deeper gene pool, with more unequal swimmers

Regardless of whether the people existing after agriculture were happier, healthier, or neither, it is undeniable that there were more of them. Agriculture both supports and requires more people to grow the crops that sustain them. Estimates vary, of course, but evidence points to an increase in the human population from 1–5 million people worldwide to a few hundred million once agriculture had become established. And a larger population doesn’t just mean scaling everything up, like buying a bigger box of cereal for a larger family. It brings qualitative changes in the way people live.

For example, more people means more kinds of diseases, particularly when those people are sedentary. When those groups of people can also store food for long periods, the opportunity arises for sequestering that food, creating in turn a society with haves and have-nots. Many authors, including Diamond and Wells, have detailed the resulting social stratification, carrying with it increased division of labor and specialization, the growth of religion and government, and countless other marks of civilization, from architecture to money. Wells suggests that agriculture also fueled a change in human attitudes toward nature, from respect to a need for control, which in turn led to some of the planetary environmental problems of today.

Scientists and scholars ranging from the late Stephen Jay Gould to José Ortega y Gasset have lamented the supposed increase in warfare and violence as people moved from hunter-gatherer to settled life. The horrific large-scale violence we see today is sometimes attributed to the impersonal nature of warfare via airplanes and missiles, but the facts are hard to come by. Contemporary hunter-gatherers vary in the amount of warfare they exhibit, and as I pointed out in the previous chapter, because of modern influences on their behavior, any conclusions about our ancestors’ violent predilections based on today’s foraging peoples should be taken with a grain of salt.

Economist Samuel Bowles examined the percentage of adult mortality attributed to warfare from archaeological sites (where deaths from weapons can be determined using marks on the skeleton) and ethnographic records around the world dating from the nineteenth century, mainly before contact with modern industrialized society.
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The data reveal a startling 14 percent of deaths from such violence, a much higher proportion than would be found in most societies today. Bowles goes on to suggest that selection at the level of the group could have increased the frequency of altruistic genes in early humans, because groups with sacrificing members would have been better able to persist in the face of frequent attacks. Whether or not Bowles is correct, his findings do not support a pacifist history of early humans that became bloody only after people became farmers. Psychologist Steven Pinker argues that human society has, in fact, become much more peaceful of late.
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More people, however, also means more genes. Not more genes in each individual, but more genes overall, as a simple result of there being more humans on Earth. While a larger population has obvious drawbacks, including overcrowding and high demand on resources such as clean water, it also has a sometimes overlooked benefit: more fodder for natural selection to act on. Evolution requires mutations, small alterations in the genes, to do its work. Beneficial traits, whether those are air-breathing lungs instead of gills or the ability to throw a spear, depend on new genes or combinations of genes, and the ultimate source of new genetic material is random mutation. Think of mutations as lottery tickets: the vast majority of them are losers, but the only way to increase your chances of winning is to buy a larger number of entries. As Cochran and Harpending point out, once the human population began expanding at a rapid clip, “favorable mutations that had previously occurred every 100,000 years or so were now showing up every 400 years.”
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And such favorable mutations spread more quickly in larger populations. Hence, a bigger population can evolve faster. John Hawks and his colleagues calculated that in the last 50,000 years, nearly 3,000 new adaptive mutations arose in Europeans.
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What this means is that the population explosion after agriculture, despite its well-known drawbacks, also carried some important positive changes that may have been overlooked. Cochran and Harpending also believe that human intelligence increased dramatically once groups became larger, via the same more-tickets-in-the-lottery mechanism.
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Adam Powell and colleagues at University College London suggest that group size, not necessarily related to the birth of agriculture but among early humans in general, was key to the uptick in cultural and technological complexity seen during the Upper Paleolithic in many parts of the world.
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Tools, weapons, art, and ritual objects all became more complex, and evidence of long-distance trading emerges in the archaeological record.

Exactly when that increase happened differs around the world, with a more rapid transition in Europe and western Asia than in northeastern Asia and Siberia. Why the variation? Powell and colleagues believe that it is much easier to lose skills like toolmaking if a group is small and only a few individuals possess the crucial knowledge. One unfortunate accident, and the village elder who transmitted information about the best place to get stones for spear tips, or a more sophisticated method for drawing on cave walls, is gone, and with that person the skills he harbored. Larger groups, or frequent migration between populations, provide some insurance against those skills being lost forever.

It is important to keep in mind that neither the benefits of human population growth, such as the flowering of genetic potential or cultural complexity, nor the more dismal consequences of agriculture, were directed. Spencer Wells looks at the advent of farming as akin to humanity diving off a cliff. Humans, he says, “divorced themselves—and us—from millions of years of evolutionary history, charting a new course into the future without a map to guide them through the pitfalls that would appear over the subsequent ten millennia.”
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He rues the “unintended consequences” of the establishment of agriculture.

The problem is, all of evolution’s consequences are unintended, and there are never any maps. Arguably, apes, by moving from trees to plains, made their world spin just as out of control as we did when we began to grow crops. Either way, no one was aiming anywhere. As I discussed in the previous chapter, all those cute cartoons showing fish anxiously, or ambitiously, gazing up the shore toward ever-more-bipedal animals that eventually tote briefcases and wear Prada are just that—cartoons. Evolution is continuous, but it is not goal-oriented. It is not as if we were on a predestined path toward enlightenment when agriculture suddenly threw a plow into the works and made us deviate into obesity and disease.

Mired in the Stone Age, or in the EEA, or somewhere

Whether agriculture was a boon or a burden, what about the idea that because our bodies and minds evolved during the millennia before agriculture came about, we are still hobbled by our ancient genes in a world that has changed beyond recognition from our days as hunter-gatherers? The notion of a mismatch between modern and ancestral humans can be seen everywhere from diet books detailing how cavemen ate to conjectures about why powerful male celebrities seek out young women. As the quotations at the start of this chapter illustrate, we often look to our evolutionary past to explain the woes of our apparently ill-adapted present.

This idea of being stuck in a world to which we are not adapted is perhaps most elaborated on by the evolutionary psychologists. Evolutionary psychology, a field that purports to explain human behavior using evolutionary principles, relies on a concept called the Environment of Evolutionary Adaptedness, or EEA. The original idea of the EEA was developed in the late 1960s and early 1970s by psychologist John Bowlby, who was interested in how children become attached to their parents and vice versa. The EEA was later used as a linchpin for examinations of adaptation in the human mind. As Leda Cosmides and John Tooby, some of the leaders in evolutionary psychology, put it:

Our species lived as hunter-gatherers 1000 times longer than as anything else. The world that seems so familiar to you and me, a world with roads, schools, grocery stores, factories, farms, and nation-states, has lasted for only an eyeblink of time when compared to our entire evolutionary history. The computer age is only a little older than the typical college student, and the industrial revolution is a mere 200 years old. Agriculture first appeared on earth only 10,000 years ago, and it wasn’t until about 5,000 years ago that as many as half of the human population engaged in farming rather than hunting and gathering. Natural selection is a slow process, and there just haven’t been enough generations for it to design circuits that are well-adapted to our post-industrial life.
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The EEA is the environment in which a particular characteristic, like the eye, or a love of sweets, evolved. It is not simply equivalent to the African savanna of 100,000 years ago, or any other single place or time. But because the human species spent so much longer on that savanna than it has in Midtown Manhattan, the evolutionary psychologists surmise that we simply have not had enough time to adapt to the modern environment. Tooby and Cosmides claim, “The key to understanding how the modern mind works is to realize that its circuits were not designed to solve the day-to-day problems of a modern American—they were designed to solve the day-to-day problems of our hunter-gatherer ancestors.”
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Hence the Stone Age mind (or genes). More simply, Edward Hagen says that the EEA “is the environment to which a species is adapted.”
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Thus, all organisms have an EEA, from fish to bacteria to elephants.

Before going any further, let me point out that I see nothing wrong with trying to explain the psychology or behavior of humans using an evolutionary framework. I do, however, find that people have a hard time viewing themselves dispassionately, and when it comes to explaining our own behavior, we have a regrettable tendency to see what we want to see and rationalize what we already want to do. That often means that if we can think of a way in which a behavior, whether it is eating junk food or having an affair, might have been beneficial in an ancestral environment, we feel vindicated, or at least justified. It’s different from “my genes made me do it,” but the end result—that we are trapped, perhaps regrettably, in a web of behavior that we inherited from our ancestors—is the same. What I am arguing in this book is that such an approach misses the real lessons of evolution, not only because it is specious to suggest that our genes dictate infidelity, but because that trap does not exist.