Cannibals and Kings (4 page)

What I find so intriguing about this discovery is that it links low fertility with diets that are high in proteins and low in carbohydrates. On the one hand, if a woman is to nurse a child successfully for three or four years she must have a high protein intake to sustain her health, body vigor, and the flow of milk. On the other hand, if she consumes too many carbohydrates she will begin to put on weight, which will trigger the resumption of ovulation. A demographic study carried out by J. K. Van Ginneken indicates that nursing women in underdeveloped countries, where the diet consists mostly of starchy grains and root crops, cannot expect to extend the interval between births beyond eighteen months. Yet nursing Bushman women, whose diet is rich in animal and plant proteins and who lack starchy staples, as I have said, manage to keep from getting pregnant four or more years after each birth. This relationship suggests that during good times hunter-collectors could rely on prolonged lactation as their principal defense against overpopulation. Conversely, a decline in the quality of the food supply would tend to bring about an increase in population. This in turn would mean either that the rate of abortion and infanticide would have to be accelerated or that still more drastic cuts in the protein ration would be needed.

I am not suggesting that the entire defense against overpopulation among our stone age ancestors rested with the lactation method. Among the Bushmen of Botswana the present rate of population growth is .5 percent per annum. This amounts to a doubling every 139 years. Had this rate been sustained for only the last 10,000 years of the old stone age, by 10,000
B.C
. the
population of the earth would have reached 604,463,000,000,000,000,000,000.

Suppose the fertile span were from sixteen years of age to forty-two. Without prolonged nursing, a woman might experience as many as twelve pregnancies. With the lactation method, the number of pregnancies comes down to six. Lowered rates of coitus in older women might further reduce the number to five. Spontaneous abortions and infant mortality caused by disease and accidents might bring the potential reproducers down to four—roughly two more than the number permissible under a system of zero population growth. The “extra” two births could then be controlled through some form of infanticide based on neglect. The optimal method would be to neglect only the girl babies, since the rate of growth in populations that do not practice monogamy is determined almost entirely by the number of females who reach reproductive age.

Our stone age ancestors were thus perfectly capable of maintaining a stationary population, but there was a cost associated with it—the waste of infant lives. This cost lurks in the background of prehistory as an ugly blight in what might otherwise be mistaken for a Garden of Eden.

The period from 30,000 to 12,000 years ago marked the climax of millions of years of slow technological evolution during which our stone age ancestors gradually perfected the tools and techniques for making a living by hunting large land animals. There are Old World habitation sites dating back hundreds of thousands of years at which archaeologists have found remains of a few pachyderms, giraffes, and buffalo, but these animals probably died natural deaths or were trapped or wounded by nonhuman predators. During this time our ancestors may have scavenged rather than hunted the meat from big game. But by 30,000 years ago the situation had changed, and bands of hunter-collectors in both the Old and New Worlds possessed the means for killing and butchering even the largest animals on a routine basis.

In Europe and Asia vast herds of reindeer, mammoth, horses, bison, and wild cattle grazed on lush grasses fed by glacial melt waters. The pursuit of these creatures came to dominate the food quest. Hunters rounded up their prey by setting fires, drove them over cliffs, and dispatched them with an arsenal of stone and bone projectile points, spears, darts, long knives, and bows and arrows. For thousands of years human predators and animal prey remained in ecological balance.

Then, about 13,000 years ago, a global warming
trend signaled the beginning of the terminal phase of the last ice age. The glaciers that had covered much of the Northern Hemisphere with mile-high sheets of ice began to back away toward Greenland. As the climate became less severe, forests of evergreens and birches invaded the grassy plains which nourished the great herds. The loss of these grazing lands in combination with the toll taken by the human predators produced an ecological catastrophe. The woolly mammoth, woolly rhinoceros, steppe bison, giant elk, European wild ass, and a whole genus of goats suddenly became extinct. While horses and cattle survived, their numbers in Europe sharply decreased. Other species like the saiga antelope and the musk ox survived only in scattered pockets in the far north. Scientists do not agree about the relative impact of the climatological changes and human predation in bringing about the extinction of these animals. Human predation definitely played a role because elephants and rhinos had managed to survive several earlier wanning trends caused by previous glacial retreats.

The collapse of the big-game hunting cultures in northern Europe was followed by the mesolithic period (or middle stone age), during which people obtained their proteins from fish, shellfish, and forest deer. In the Middle East (what is now southern Turkey, Iraq, Iran, Syria, Jordan, and Israel), where the age of the big-game hunters had come to an end much earlier than in the north, the pattern of subsistence became even more diversified. Here people turned from hunting giant wild cattle and red deer to preying on smaller species such as sheep, goats, and antelope and paid increasing attention to fish, crabs and other shellfish, birds, snails, acorns, pistachios and other nuts, wild legumes, and wild grains. Kent Flannery of the University
of Michigan has called this system “broad spectrum” hunting and collecting. The retreat of the glaciers and the intensification of big-game hunting did not have precisely the same consequences in Europe and the Middle East, but both regions probably suffered similar environmental depletions which raised the costs of obtaining animal proteins. According to Karl Butzer, most of Turkey, northeastern Iraq, and Iran were treeless during the last ice age, and this would have facilitated the hunting of herd animals. True, the reforestation that occurred at the end of the glacial period was not as extensive as in Europe, but this may actually have made the ecological crisis in the Middle East more severe because of a deficit of both open-country and forest species.

Turning to North and South America, one can see the same process at work. The terminal phase of the last ice age represented the peak of specialized big-game hunting in the New World. At sites in Venezuela, Peru, Mexico, Idaho, and Nevada archaeologists have found beautifully crafted leaf-shaped projectile points, blades, and burins dating from 13,000 to 9000
B.C.
, some of which are associated with extinct species of antelope, horses, camels, mammoth, mastodon, giant ground sloths, and giant rodents. Between 11,000 and 8000
B.C.
big-game hunters equipped with fluted and channeled points were active over a wide expanse of North America, but by 7000
B.C
. predation and the climatological changes brought about by the receding glaciers had resulted in the total extinction of thirty-two whole genera of large New World animals including horses, giant bison, oxen, elephant, camels, antelope, pigs, ground sloths, and giant rodents.

Paul C. Martin of the University of Arizona has suggested that the ancestors of the American Indians killed
off all of these large animals—called collectively the “Pleistocene Megafauna”—in one short burst of intense predation. Martin attributes this rapid extinction to the fact that the animals had never been hunted by human beings prior to the arrival of bands of Siberian migrants who crossed the Bering Straits land bridge 11,000 years ago. We now know, however, that the discovery of America by migrants from Asia took place much earlier—at least 15,000 and possibly even 70,000 years ago. Although Martin’s overall theory is thus disproven, his idea of rapid extinction deserves careful consideration. Using a computer program to simulate various kill rates practiced by a small initial human population, Martin has shown that all the big animals from Canada to the Gulf Coast could have been wiped out in three centuries if the hunters had permitted their own population to double each generation—a rate of growth well within the reproductive capacity of paleolithic hunters.

Martin’s scenario remains useful as an illustration of the vulnerability of large, slow-breeding species to hunter-collectors who decide to increase their kill rates as a result of reproductive pressures and threats to their standard of living. I suspect that the extinction was caused not by any sharp increase in the human population, but simply by an attempt to maintain dietary standards and low abortion and infanticide rates in the face of fewer numbers of prey animals.

After the decline of the New World big-game hunters, cultures appeared in the Americas whose subsistence systems resembled those of the Middle Eastern “broad spectrum” hunters and collectors. Details of the process of intensification and depletion are clearest in the remarkable studies carried out in the Tehuacán Valley under the direction of Richard MacNeish of the Peabody Museum of Archaeology. The Tehuacán Valley, a long, narrow depression located in the southeast part of the Mexican state of Puebla at an altitude of 4,500 feet, is surrounded by high mountains that give it a hot, dry climate. Here, during the Ajuereado period (7000–5000
B.C
.), horses and antelope were hunted to extinction. The hunters then intensified the predation of jackrabbits and giant turtle, and these too soon became extinct. MacNeish estimates that at this time meat comprised 89 to 76 percent of the hunters’ total caloric intake at maximum and minimum seasons of the year. During the following El Riego (5000–3400
B.C
), Coxcatlán (3400–2300
B.C.
), and Abejas (2300–1850
B.C.
) periods, the maximum-minimum seasonal calorie percentage of meat fell to 69–31, 62–23, and 47–15 percent, respectively. By about 800
B.C
., when fully
sedentary villages based on agriculture were finally established in the valley, the proportion of calories provided by animal proteins had fallen still farther and the difference in eating habits between hunting and non-hunting seasons had virtually disappeared. Eventually, as we shall see later on, meat in ancient Mexico was to become a luxury whose production and consumption was the occasion for some of the must brutal institutions in human history.

The implacable decline in the proportion of animal protein in the Tehuacán diet was the result of a continuous series of intensifications and depletions, accompanied by improvements in the technology of hunting. As each species was depleted, the hunters attempted to compensate for the declining return in the effort they invested by using more efficient hunting weapons and techniques. Lances, spear-throwers, darts, and finally the bow and arrow were pressed into service, all to no avail.

According to MacNeish’s estimates, the labor efficiency (calories obtained per calorie expended) of Ajuereado rabbit drives was 2.5:1. Lance ambushing started with an efficiency of 3.2:1 in the early Ajuereado period but fell to 1:1 in Abejas and then died out. Dart stalking of deer began at 7:1 but dropped to about 4:1 as the animal became less plentiful. Later the bow and arrow provided a new high of about 8:1 or 9:1, but by then game was so scarce that meat could contribute only insignificantly to the diet.

As they fought their long and futile delaying action against the consequences of the depletion of animal species, the people of Tehuacán gradually shifted their primary subsistence effort away from animals toward plants. Intensification of plant production resulted in a slowly increasing proportion of domesticated plants
among the “broad spectrum” that was initially obtained entirely by collecting activities. By late El Riego times the hunting bands had succeeded in domesticating squash, amaranth, chili peppers, and avocados. They added maize and beans during the Coxcatlán period, and these crops steadily gained in importance as settlements increased in size and became more sedentary.

MacNeish estimates that the percentage calorie contribution of domesticated and/or cultivated plants was only 1 percent during the El Riego period, 8 percent during Coxcatlán, and 21 percent during Abejas. Even by the time the first permanent settlements appeared, domesticated and/or cultivated plants provided only 42 percent of the total caloric intake.

As in the case of hunting, intensification of farming gave rise to a series of technological advances. Horticulture, or rudimentary gardening, was followed by agriculture, which came to rely more and more on irrigation. The labor efficiencies of these different systems of food production advanced from 10:1 to 30:1 to 50:1. MacNeish does not discuss the possibility that successive declines in labor efficiency prompted the shifts to agriculture and irrigation. And I would not insist that such declines are always necessary to explain the shift to more efficient modes of farming. The decline in the production of animal protein could after all be compensated only by raising the output of plant proteins. The important point is, despite the fact that irrigation agriculture was five times more productive per man-hour than horticulture, the entire 9,000-year sequence of intensifications, depletions, and technological innovations resulted in an overall deterioration in nutritional status.