The World Until Yesterday: What Can We Learn from Traditional Societies? (77 page)

So accustomed are we in the First World to predictable amounts of food at predictable times each day that we find it hard to imagine the often-unpredictable fluctuations between frequent food shortages and infrequent gluts that constituted the pattern of life for almost all people throughout human evolution until recently, and that remain so in many parts of the world today. I’ve often encountered such fluctuations during my fieldwork among New Guineans still subsisting by farming and hunting. For example, in one memorable incident I hired a dozen men to carry heavy equipment all day over a steep trail up to a mountain campsite. We arrived at the camp just before sunset, expecting to meet there another group of porters carrying food, and instead found that they had not arrived because of a misunderstanding. Faced with hungry, exhausted men and no food, I expected to be lynched. Instead, my carriers just laughed and said, “Orait, i nogat kaikai, i samting nating, yumi slip nating, enap yumi kaikai tumora” (“OK, so there’s no food, it’s no big deal, we’ll just sleep on empty stomachs tonight and wait until tomorrow to eat”). Conversely, on other
occasions at which pigs are slaughtered, my New Guinea friends have a gluttonous feast lasting several days, when food consumption shocks even me (formerly rated by my friends as a bottomless pit) and some people become seriously ill from overeating.

Table 11.2. Examples of gluttony when food is abundantly available

Daniel Everett (
Don’t Sleep, There Are Snakes,
pages 76
–
77
). “They [the Piraha Indians of South America] enjoy eating. Whenever there is food available in the village, they eat it all…. [But] missing a meal or two, or even going without eating for a day, is taken in stride. I have seen people dance for three days with only brief breaks…. Pirahas [visiting] in the city for the first time are always surprised by Western eating habits, especially the custom of three meals a day. For their first meal outside of the village, most Pirahas eat greedily—large quantities of proteins and starch. For the second meal they eat the same. By the third meal they begin to show frustration. They look puzzled. Often they ask, ‘Are we eating again?’ Their own practice of eating food when it is available until it is gone now conflicts with the circumstances in which food is always available and never gone. Often after a visit of three to six weeks, a Piraha [originally weighing between 100 and 125 pounds] will return as much as 30 pounds overweight to the village, rolls of fat on their belly and thighs.”

Allan Holmberg (
Nomads of the Long Bow,
page 89
). “The quantities of food eaten on occasion [by the Siriono Indians of Bolivia] are formidable. It is not uncommon for four people to eat a peccary of 60 pounds at a single sitting. When meat is abundant, a man may consume as much as 30 pounds within 24 hours. On one occasion, when I was present, two men ate six spider monkeys, weighing from 10 to 15 pounds apiece, in a single day, and complained of being hungry that night.”

Lidio Cipriani (
The Andaman Islanders,
page 54
). “Cleaning themselves, to the Onges [of the Andaman Islands in the Indian Ocean], means painting themselves to ward off evil and to remove, so they said, the smell of pig fat after the colossal orgies which follow a particularly good hunt, when even they find the stench too much. These orgies, which give them appalling indigestion for days, are followed by an apparently instinctive variation of their diet to raw or cooked vegetable foods. On three occasions from 1952 to 1954 I was present at one of the solemn pork and honey orgies. The Onges ate almost until they burst, and then, hardly able to move, cleaned up by a grand painting session.”

Ditto,
page 117
. “As the tide goes down, the shoals [of fish called pilchards] are caught in the reefs stretching out to sea all around the island and the Onges leave everything to man-handle the canoes from pool to pool and fill them to overflowing. The water is almost saturated with fish, and the Onges go on and on until they have nothing more they can use to hold the catch. Nowhere else in the world have I seen anything like this wholesale slaughter. The pilchards of the Andamans are rather larger than usual, some weighing as much as half a kilogram or more…. Men, women and children work feverishly, plunging their hands into the heaving mass of fish so that they reek of it for days…. Everyone cooks and eats at the same time until (temporarily) unable to eat anymore, when the rest of the haul is laid on improvised racks with fires of green wood making smoke underneath. When, a few days later, all is gone, fishing begins again. And so life goes on for weeks, until the shoals have passed the islands.”

These anecdotes illustrate how people accommodate to the pendulum of feast and famine that swung often but irregularly through our evolutionary history. In
Chapter 8
I summarized the reasons for the frequency of famine under traditional living conditions: food shortages associated with day-to-day variation in hunting success, short bouts of inclement weather, predictable seasonal variation in food abundance through the year, and unpredictable year-to-year variation in weather; in many societies, little or no ability to accumulate and store surplus food; and lack of state governments or other means to organize and integrate food storage, transport, and exchanges over large areas. Conversely,
Table 11.2
collects some anecdotes of gluttony around the world at times when food becomes available in abundance to traditional societies.

Under these traditional conditions of starve-and-gorge existence, those individuals with a thrifty genotype would be at an advantage, because they could store more fat in surplus times, burn fewer calories in spartan times, and hence better survive starvation. To most humans until recently, our modern Western fear of obesity and our diet clinics would have seemed ludicrous, as the exact reverse of traditional good sense. The genes that today predispose us to diabetes may formerly have helped us to survive famine. Similarly, our “taste” for sweet or fatty foods, like our taste for salt, predisposes us to diabetes and hypertension now that those tastes can be satisfied so easily, but formerly guided us to seek valuable rare nutrients. Note again, just as we saw for hypertension, the evolutionary irony. Those of us whose ancestors best survived starvation on Africa’s savannahs tens of thousands of years ago are now the ones at highest risk of dying from diabetes linked to food abundance.

Thus, the starve-and-gorge lifestyle traditionally shared by all human populations resulted in natural selection of genes for a thrifty genotype that served us well under those starve-and-gorge conditions, but that has then caused virtually all populations to end up with a propensity for diabetes under modern Western conditions of unremitting food abundance. But why, by this reasoning, are Pima Indians and Nauruans unusual in their world-record diabetes prevalences? I think that’s because they were subjected in the recent past to world-record strengths of selection for a thrifty genotype. The Pimas started out sharing with other Native
Americans their exposure to periodic starvation. They then experienced a further prolonged bout of starvation and selection in the late 19th century, when white settlers ruined their crops by cutting off their sources of irrigation water. Those Pimas who survived were individuals who were genetically even better adapted than other Native Americans to survive starvation by storing fat whenever food had become available. As for Nauruans, they suffered two extreme bouts of natural selection for thrifty genes, followed by an extreme bout of coca-colonization. First, like other Pacific Islanders, but unlike the inhabitants of continental regions, their population was founded by people who undertook inter-island canoe voyages lasting several weeks. In numerous attested examples of such lengthy voyages, many or most of the canoe occupants died of starvation, and only those who were originally the fattest survived. That is why Pacific Islanders in general tend to be heavy people. Second, the Nauruans were then set apart even from most other Pacific Islanders by their extreme starvation and mortality during the Second World War, leaving the population presumably even more enriched in diabetes susceptibility genes. After the war, their newfound wealth based on phosphate royalties, their superabundant food, and their diminished need for physical activity led to exceptional obesity.

Three lines of human evidence and two animal models support the plausibility of Neel’s thrifty-gene hypothesis. Non-diabetic Nauruans, Pima Indians, African Americans, and Aboriginal Australians have postprandial levels of plasma insulin (in response to an oral glucose load) several times those of Europeans. New Guinea Highlanders, Aboriginal Australians, Maasai tribespeople of Kenya, and other peoples with traditional lifestyles have blood glucose levels far below those of white Americans. Given ample food, diabetes-prone populations of Pacific Islanders, Native Americans, and Aboriginal Australians do exhibit more propensity to obesity than do Europeans: first they gain weight, then they develop diabetes. As for animal models, laboratory rats carrying genes predisposing them to diabetes and obesity survive starvation better than do normal rats, illustrating the advantage of those genes under occasional conditions of famine. The Israeli sand rat, which is adapted to a desert environment with frequent scarcities of food, develops high insulin levels, insulin resistance, obesity, and diabetes when maintained in the laboratory on a “Westernized rat diet” with abundant food. But those symptoms reverse
when the sand rat’s food is restricted. Hence diabetes-prone laboratory rats and Israeli sand rats serve as models both of the benefits of thrifty genes and of hair-triggered insulin release under “traditional rat conditions” of starve-and-gorge, and of the costs of those genes under “supermarket rat conditions.”

Diabetologists used to point to Pimas and Nauruans as the glaring exceptions of high diabetes prevalence, standing out from a world in which the relatively low diabetes prevalence of Europeans was taken as the norm. But the information that has become available in recent decades shows that, instead, Europeans are the exception in their low prevalence, contrasting with the high prevalence reached by Westernized populations of everyone else. Pimas and Nauruans are “merely” the highest of that normal high prevalence, already approached closely by some Aboriginal Australians and New Guinean groups. For every well-studied large non-European population grouping, we now know of some Westernized subgroup with a prevalence above 11%, usually above 15%: Native Americans, North Africans, sub-Saharan Black Africans, Middle Easterners, Indians, East Asians, New Guineans, Aboriginal Australians, Micronesians, and Polynesians. Compared to that norm, Europeans, and overseas Europeans in Australia, Canada, New Zealand, and the U.S., are unique among the modern world’s populations in their relatively low prevalence. All 41 national European values for the prevalence of diabetes (
Table 11.1
, first row) fall between 2% and 10%, with a mean value of only 6%.

That’s astonishing when one reflects that Europeans in Europe itself and overseas are the world’s richest and best-fed people, and the originators of the Western lifestyle. We refer to our indolent, obese, supermarket way of life as Western precisely because it arose first among Europeans and white Americans and is only now spreading to other peoples. How can we account for this paradox? Why don’t Europeans now have the highest, rather than the lowest, prevalence of diabetes?

Several experts in the study of diabetes have suggested to me informally that perhaps Europeans traditionally had little exposure to famine,
so that they would have undergone little selection for a thrifty genotype. Actually, though, history provides abundant documentation of famines that caused widespread severe mortality in medieval and Renaissance Europe and earlier. Those repeated famines should have selected for thrifty genes in Europe, just as everywhere else. Instead, a more promising hypothesis is based on Europe’s recent food history since the Renaissance. The periodic widespread and prolonged famines that used to rack Europe, like the rest of the world, disappeared between about 1650 and 1900 at different times in different parts of Europe, beginning in the late 1600s in Britain and the Netherlands, and continuing into the late 1800s in southern France and southern Italy. With one famous exception, Europe’s famines were ended by a combination of four factors: increasingly efficient state intervention that rapidly redistributed surplus grain to famine areas; increasingly efficient food transport by land and especially by sea; increasingly diversified European agriculture after Columbus’s voyage of AD 1492, thanks to European voyagers bringing back many New World crops (such as potatoes and corn); and, finally, Europe’s reliance not on irrigation agriculture (as in many populous areas of the world outside Europe) but instead on rain agriculture, which reduced the risk of a crop failure too widespread to be solved by food transport within Europe.

The famous exception to the end of Europe’s famines was of course the Irish potato famine of the 1840s. Actually, that was the exception that proved the rule, by illustrating what happened even in Europe when the first three above-mentioned factors ending famines elsewhere in Europe didn’t operate. The Irish potato famine was due to a disease of a single strain of potato in an agricultural economy that was unusual in Europe in its reliance on that single crop. The famine occurred on an island (Ireland) governed by an ethnically different state centered on another island (Britain) and notorious for the inefficiency or lack of motivation of its response to the Irish famine.

These facts of Europe’s food history lead me to offer the following speculation. Several centuries before the advent of modern medicine, Europeans, like modern Nauruans, may have undergone an epidemic of diabetes that resulted from the new reliability of adequate food supplies, and that eliminated most diabetes-prone bearers of the thrifty genotype, leaving Europe with its low prevalence of diabetes today. Those gene-bearers may have been undergoing elimination in Europe for centuries, as a result of
many infants of diabetic mothers dying at birth, diabetic adults dying younger than other adults, and children and grandchildren of those diabetic adults dying of neglect or reduced material support. However, there would have been big differences between that postulated cryptic earlier European epidemic and the well-documented modern epidemics among Nauruans and so many other peoples today. In the modern epidemics, abundant and continually reliable food arrived suddenly—within a decade for Nauruans, and within just a month for Yemenite Jews. The results were sharply peaked surges in diabetes’s prevalence to 20%–50% that have been occurring right under the eyes of modern diabetologists. Those increases will probably wane quickly (as already observed among Nauruans), as individuals with a thrifty genotype become eliminated by natural selection within a mere generation or two. In contrast, Europe’s food abundance increased gradually over the course of several centuries. The result would have been an imperceptibly slow rise in diabetes prevalence in Europe, between the 1400s and the 1700s, long before there were any diabetologists to take note. In effect, Pimas, Nauruans, Wanigelas, educated urban Indians, and citizens of wealthy oil-producing Arab nations are telescoping into a single generation the lifestyle changes and consequent rise and fall of diabetes that unfolded over the course of many centuries in Europe.