Guns, Germs And Steel Part 7

Eurasia Sub-Saharan Africa

The Americas Australia Candidates 72 51

24 1 Domesticated species 13 0

1 0 Percentage of Candidates domesticated 18% 0%

4% 0%

A "candidate" is defined as a species of terrestrial, herbivorous or omnivorous, wild mammal weighing on the average over 100 pounds.

One reason is simple. Eurasia has the largest number of big terrestrial wild mammal species, whether or not ancestral to a domesticated species. Let's define a "candidate for domestication" as any terrestrial herbivorous or omnivorous mammal species (one not predominantly a carnivore) weighing on the average over 100 pounds (45 kilograms). Table 9.2 shows that Eurasia has the most candidates, 72 species, just as it has the most species in many other plant and animal groups. That's because Eurasia is the world's largest landma.s.s, and it's also very diverse ecologically, with habitats ranging from extensive tropical rain forests, through temperate forests, deserts, and marshes, to equally extensive tundras. Sub-Saharan Africa has fewer candidates, 51 species, just as it has fewer species in most other plant and animal groups-because it's smaller and ecologically less diverse than Eurasia. Africa has smaller areas of tropical rain forest than does Southeast Asia, and no temperate habitats at all beyond lat.i.tude 37 degrees. As I discussed in Chapter 1, the Americas may formerly have had almost as many candidates as Africa, but most of America's big wild mammals (including its horses, most of its camels, and other species likely to have been domesticated had they survived) became extinct about 13,000 years ago. Australia, the smallest and most isolated continent, has always had far fewer species of big wild mammals than has Eurasia, Africa, or the Americas. Just as in the Americas, in Australia all of those few candidates except the red kangaroo became extinct around the time of the continent's first colonization by humans.

Thus, part of the explanation for Eurasia's having been the main site of big mammal domestication is that it was the continent with the most candidate species of wild mammals to start out with, and lost the fewest candidates to extinction in the last 40,000 years. But the numbers in Table 9.2 warn us that that's not the whole explanation. It's also true that the percentage percentage of candidates actually domesticated is highest in Eurasia (18 percent), and is especially low in sub-Saharan Africa (no species domesticated out of 51 candidates!). Particularly surprising is the large number of species of African and American mammals that were never domesticated, despite their having Eurasian close relatives or counterparts that were domesticated. Why were Eurasia's horses domesticated, but not Africa's zebras? Why Eurasia's pigs, but not American peccaries or Africa's three species of true wild pigs? Why Eurasia's five species of wild cattle (aurochs, water buffalo, yak, gaur, banteng), but not the African buffalo or American bison? Why the Asian mouflon sheep (ancestor of our domestic sheep), but not North American bighorn sheep? of candidates actually domesticated is highest in Eurasia (18 percent), and is especially low in sub-Saharan Africa (no species domesticated out of 51 candidates!). Particularly surprising is the large number of species of African and American mammals that were never domesticated, despite their having Eurasian close relatives or counterparts that were domesticated. Why were Eurasia's horses domesticated, but not Africa's zebras? Why Eurasia's pigs, but not American peccaries or Africa's three species of true wild pigs? Why Eurasia's five species of wild cattle (aurochs, water buffalo, yak, gaur, banteng), but not the African buffalo or American bison? Why the Asian mouflon sheep (ancestor of our domestic sheep), but not North American bighorn sheep?

DID ALL THOSE peoples of Africa, the Americas, and Australia, despite their enormous diversity, nonetheless share some cultural obstacles to domestication not shared with Eurasian peoples? For example, did Africa's abundance of big wild mammals, available to kill by hunting, make it superfluous for Africans to go to the trouble of tending domestic stock? peoples of Africa, the Americas, and Australia, despite their enormous diversity, nonetheless share some cultural obstacles to domestication not shared with Eurasian peoples? For example, did Africa's abundance of big wild mammals, available to kill by hunting, make it superfluous for Africans to go to the trouble of tending domestic stock?

The answer to that question is unequivocal: No! The interpretation is refuted by five types of evidence: rapid acceptance of Eurasian domesticates by non-Eurasian peoples, the universal human penchant for keeping pets, the rapid domestication of the Ancient Fourteen, the repeated independent domestications of some of them, and the limited successes of modern efforts at further domestications.

First, when Eurasia's Major Five domestic mammals reached sub-Saharan Africa, they were adopted by the most diverse African peoples wherever conditions permitted. Those African herders thereby achieved a huge advantage over African hunter-gatherers and quickly displaced them. In particular, Bantu farmers who acquired cows and sheep spread out of their homeland in West Africa and within a short time overran the former hunter-gatherers in most of the rest of sub-Saharan Africa. Even without acquiring crops, Khoisan peoples who acquired cows and sheep around 2,000 years ago displaced Khoisan hunter-gatherers over much of southern Africa. The arrival of the domestic horse in West Africa transformed warfare there and turned the area into a set of kingdoms dependent on cavalry. The only factor that prevented horses from spreading beyond West Africa was trypanosome diseases borne by tsetse flies.

The same pattern repeated itself elsewhere in the world, whenever peoples lacking native wild mammal species suitable for domestication finally had the opportunity to acquire Eurasian domestic animals. European horses were eagerly adopted by Native Americans in both North and South America, within a generation of the escape of horses from European settlements. For example, by the 19th century North America's Great Plains Indians were famous as expert horse-mounted warriors and bison hunters, but they did not even obtain horses until the late 17th century. Sheep acquired from Spaniards similarly transformed Navajo Indian society and led to, among other things, the weaving of the beautiful woolen blankets for which the Navajo have become renowned. Within a decade of Tasmania's settlement by Europeans with dogs, Aboriginal Tasmanians, who had never before seen dogs, began to breed them in large numbers for use in hunting. Thus, among the thousands of culturally diverse native peoples of Australia, the Americas, and Africa, no universal cultural taboo stood in the way of animal domestication.

Surely, if some local wild mammal species of those continents had been domesticable, some Australian, American, and African peoples would have domesticated them and gained great advantage from them, just as they benefited from the Eurasian domestic animals that they immediately adopted when those became available. For instance, consider all the peoples of sub-Saharan Africa living within the range of wild zebras and buffalo. Why wasn't there at least one African hunter-gatherer tribe that domesticated those zebras and buffalo and that thereby gained sway over other Africans, without having to await the arrival of Eurasian horses and cattle? All these facts indicate that the explanation for the lack of native mammal domestication outside Eurasia lay with the locally available wild mammals themselves, not with the local peoples.

A SECOND TYPE SECOND TYPE of evidence for the same interpretation comes from pets. Keeping wild animals as pets, and taming them, const.i.tute an initial stage in domestication. But pets have been reported from virtually all traditional human societies on all continents. The variety of wild animals thus tamed is far greater than the variety eventually domesticated, and includes some species that we would scarcely have imagined as pets. of evidence for the same interpretation comes from pets. Keeping wild animals as pets, and taming them, const.i.tute an initial stage in domestication. But pets have been reported from virtually all traditional human societies on all continents. The variety of wild animals thus tamed is far greater than the variety eventually domesticated, and includes some species that we would scarcely have imagined as pets.

For example, in the New Guinea villages where I work, I often see people with pet kangaroos, possums, and birds ranging from flycatchers to ospreys. Most of these captives are eventually eaten, though some are kept just as pets. New Guineans even regularly capture chicks of wild ca.s.sowaries (an ostrich-like large, flightless bird) and raise them to eat as a delicacy-even though captive adult ca.s.sowaries are extremely dangerous and now and then disembowel village people. Some Asian peoples tame eagles for use in hunting, although those powerful pets have also been known on occasion to kill their human handlers. Ancient Egyptians and a.s.syrians, and modern Indians, tamed cheetahs for use in hunting. Paintings made by ancient Egyptians show that they further tamed (not surprisingly) hoofed mammals such as gazelles and hartebeests, birds such as cranes, more surprisingly giraffes (which can be dangerous), and most astonis.h.i.+ngly hyenas. African elephants were tamed in Roman times despite the obvious danger, and Asian elephants are still being tamed today. Perhaps the most unlikely pet is the European brown bear (the same species as the American grizzly bear), which the Ainu people of j.a.pan regularly regularly captured as young animals, tamed, and reared to kill and eat in a ritual ceremony. captured as young animals, tamed, and reared to kill and eat in a ritual ceremony.

Thus, many wild animal species reached the first stage in the sequence of animal-human relations leading to domestication, but only a few emerged at the other end of that sequence as domestic animals. Over a century ago, the British scientist Francis Galton summarized this discrepancy succinctly: "It would appear that every wild animal has had its chance of being domesticated, that [a] few...were domesticated long ago, but that the large remainder, who failed sometimes in only one small particular, are destined to perpetual wildness."

DATES OF DOMESTICATION provide a third line of evidence confirming Galton's view that early herding peoples quickly domesticated all big mammal species suitable for being domesticated. All species for whose dates of domestication we have archaeological evidence were domesticated between about 8000 and 2500 provide a third line of evidence confirming Galton's view that early herding peoples quickly domesticated all big mammal species suitable for being domesticated. All species for whose dates of domestication we have archaeological evidence were domesticated between about 8000 and 2500 B.C. B.C.-that is, within the first few thousand years of the sedentary farming-herding societies that arose after the end of the last Ice Age. As summarized in Table 9.3, the era of big mammal domestication began with the sheep, goat, and pig and ended with camels. Since 2500 B.C. B.C. there have been no significant additions. there have been no significant additions.

It's true, of course, that some small mammals were first domesticated long after 2500B.C. For example, rabbits were not domesticated for food until the Middle Ages, mice and rats for laboratory research not until the 20th century, and hamsters for pets not until the 1930s. The continuing development of domesticated small mammals isn't surprising, because there are literally thousands of wild species as candidates, and because they were of too little value to traditional societies to warrant the effort of raising them. But big mammal domestication virtually ended 4,500 years ago. By then, all of the world's 148 candidate big species must have been tested innumerable times, with the result that only a few pa.s.sed the test and no other suitable ones remained. For example, rabbits were not domesticated for food until the Middle Ages, mice and rats for laboratory research not until the 20th century, and hamsters for pets not until the 1930s. The continuing development of domesticated small mammals isn't surprising, because there are literally thousands of wild species as candidates, and because they were of too little value to traditional societies to warrant the effort of raising them. But big mammal domestication virtually ended 4,500 years ago. By then, all of the world's 148 candidate big species must have been tested innumerable times, with the result that only a few pa.s.sed the test and no other suitable ones remained.

STILL A FOURTH line of evidence that some mammal species are much more suitable than others is provided by the repeated independent domestications of the same species. Genetic evidence based on the portions of our genetic material known as mitochondrial DNA recently confirmed, as had long been suspected, that humped cattle of India and humpless European cattle were derived from two separate populations of wild ancestral cattle that had diverged hundreds of thousands of years ago. That is, Indian peoples domesticated the local Indian subspecies of wild aurochs, Southwest Asians independently domesticated their own Southwest Asian subspecies of aurochs, and North Africans may have independently domesticated the North African aurochs. line of evidence that some mammal species are much more suitable than others is provided by the repeated independent domestications of the same species. Genetic evidence based on the portions of our genetic material known as mitochondrial DNA recently confirmed, as had long been suspected, that humped cattle of India and humpless European cattle were derived from two separate populations of wild ancestral cattle that had diverged hundreds of thousands of years ago. That is, Indian peoples domesticated the local Indian subspecies of wild aurochs, Southwest Asians independently domesticated their own Southwest Asian subspecies of aurochs, and North Africans may have independently domesticated the North African aurochs.

Similarly, wolves were independently domesticated to become dogs in the Americas and probably in several different parts of Eurasia, including China and Southwest Asia. Modern pigs are derived from independent sequences of domestication in China, western Eurasia, and possibly other areas as well. These examples reemphasize that the same few suitable wild species attracted the attention of many different human societies.

THE FAILURES OF modern efforts provide a final type of evidence that past failures to domesticate the large residue of wild candidate species arose from shortcomings of those species, rather than from shortcomings of ancient humans. Europeans today are heirs to one of the longest traditions of animal domestication on Earth-that which began in Southwest Asia around 10,000 years ago. Since the fifteenth century, Europeans have spread around the globe and encountered wild mammal species not found in Europe. European settlers, such as those that I encounter in New Guinea with pet kangaroos and possums, have tamed or made pets of many local mammals, just as have indigenous peoples. European herders and farmers emigrating to other continents have also made serious efforts to domesticate some local species. modern efforts provide a final type of evidence that past failures to domesticate the large residue of wild candidate species arose from shortcomings of those species, rather than from shortcomings of ancient humans. Europeans today are heirs to one of the longest traditions of animal domestication on Earth-that which began in Southwest Asia around 10,000 years ago. Since the fifteenth century, Europeans have spread around the globe and encountered wild mammal species not found in Europe. European settlers, such as those that I encounter in New Guinea with pet kangaroos and possums, have tamed or made pets of many local mammals, just as have indigenous peoples. European herders and farmers emigrating to other continents have also made serious efforts to domesticate some local species.

TABLE 9.3 9.3 Approximate Dates of First Attested Evidence for Domestication of Large Mammal Species Approximate Dates of First Attested Evidence for Domestication of Large Mammal Species

Species Date (B.C.) Place Dog 10,000 Southwest Asia, China, North America Sheep 8,000 Southwest Asia Goat 8,000 Southwest Asia Pig 8,000 China, Southwest Asia Cow 6,000 Southwest Asia, India, (?)North Africa Horse 4,000 Ukraine Donkey 4,000 Egypt Water buffalo 4,000 China?

Llama / alpaca 3,500 Andes Bactrian camel 2,500 Central Asia Arabian camel 2,500 Arabia

For the other four domesticated large mammal species-reindeer, yak, gaur, and banteng-there is as yet little evidence concerning the date of domestication. Dates and places shown are merely the earliest ones attested to date; domestication may actually have begun earlier and at a different location.

In the 19th and 20th centuries at least six large mammals-the eland, elk, moose, musk ox, zebra, and American bison-have been the subjects of especially well-organized projects aimed at domestication, carried out by modern scientific animal breeders and geneticists. For example, eland, the largest African antelope, have been undergoing selection for meat quality and milk quant.i.ty in the Askaniya-Nova Zoological Park in the Ukraine, as well as in England, Kenya, Zimbabwe, and South Africa; an experimental farm for elk (red deer, in British terminology) has been operated by the Rowett Research Inst.i.tute at Aberdeen, Scotland; and an experimental farm for moose has operated in the Pechero-Ilych National Park in Russia. Yet these modern efforts have achieved only very limited successes. While bison meat occasionally appears in some U.S. supermarkets, and while moose have been ridden, milked, and used to pull sleds in Sweden and Russia, none of these efforts has yielded a result of sufficient economic value to attract many ranchers. It is especially striking that recent attempts to domesticate eland within Africa itself, where its disease resistance and climate tolerance would give it a big advantage over introduced Eurasian wild stock susceptible to African diseases, have not caught on.

Thus, neither indigenous herders with access to candidate species over thousands of years, nor modern geneticists, have succeeded in making useful domesticates of large mammals beyond the Ancient Fourteen, which were domesticated by at least 4,500 years ago. Yet scientists today could undoubtedly, if they wished, fulfill for many species that part of the definition of domestication that specifies the control of breeding and food supply. For example, the San Diego and Los Angeles zoos are now subjecting the last surviving California condors to a more draconian control of breeding than that imposed upon any domesticated species. All individual condors have been genetically identified, and a computer program determines which male shall mate with which female in order to achieve human goals (in this case, to maximize genetic diversity and thereby preserve this endangered bird). Zoos are conducting similar breeding programs for many other threatened species, including gorillas and rhinos. But the zoos' rigorous selection of California condors shows no prospects of yielding an economically useful product. Nor do zoos' efforts with rhinos, although rhinos offer up to over three tons of meat on the hoof. As we shall now see, rhinos (and most other big mammals) present insuperable obstacles to domestication.

IN ALL, OF the world's 148 big wild terrestrial herbivorous mammals-the candidates for domestication-only 14 pa.s.sed the test. Why did the other 134 species fail? To which conditions was Francis Galton referring, when he spoke of those other species as "destined to perpetual wildness"? the world's 148 big wild terrestrial herbivorous mammals-the candidates for domestication-only 14 pa.s.sed the test. Why did the other 134 species fail? To which conditions was Francis Galton referring, when he spoke of those other species as "destined to perpetual wildness"?

The answer follows from the Anna Karenina Anna Karenina principle. To be domesticated, a candidate wild species must possess many different characteristics. Lack of any single required characteristic dooms efforts at domestication, just as it dooms efforts at building a happy marriage. Playing marriage counselor to the zebra / human couple and other ill-sorted pairs, we can recognize at least six groups of reasons for failed domestication. principle. To be domesticated, a candidate wild species must possess many different characteristics. Lack of any single required characteristic dooms efforts at domestication, just as it dooms efforts at building a happy marriage. Playing marriage counselor to the zebra / human couple and other ill-sorted pairs, we can recognize at least six groups of reasons for failed domestication.

Diet. Every time that an animal eats a plant or another animal, the conversion of food bioma.s.s into the consumer's bioma.s.s involves an efficiency of much less than 100 percent: typically around 10 percent. That is, it takes around 10,000 pounds of corn to grow a 1,000-pound cow. If instead you want to grow 1,000 pounds of carnivore, you have to feed it 10,000 pounds of herbivore grown on 100,000 pounds of corn. Even among herbivores and omnivores, many species, like koalas, are too finicky in their plant preferences to recommend themselves as farm animals.

As a result of this fundamental inefficiency, no mammalian carnivore has ever been domesticated for food. (No, it's not because its meat would be tough or tasteless: we eat carnivorous wild fish all the time, and I can personally attest to the delicious flavor of lion burger.) The nearest thing to an exception is the dog, originally domesticated as a sentinel and hunting companion, but breeds of dogs were developed and raised for food in Aztec Mexico, Polynesia, and ancient China. However, regular dog eating has been a last resort of meat-deprived human societies: the Aztecs had no other domestic mammal, and the Polynesians and ancient Chinese had only pigs and dogs. Human societies blessed with domestic herbivorous mammals have not bothered to eat dogs, except as an uncommon delicacy (as in parts of Southeast Asia today). In addition, dogs are not strict carnivores but omnivores: if you are so naive as to think that your beloved pet dog is really a meat eater, just read the list of ingredients on your bag of dog food. The dogs that the Aztecs and Polynesians reared for food were efficiently fattened on vegetables and garbage.

Growth Rate. To be worth keeping, domesticates must also grow quickly. That eliminates gorillas and elephants, even though they are vegetarians with admirably nonfinicky food preferences and represent a lot of meat. What would-be gorilla or elephant rancher would wait 15 years for his herd to reach adult size? Modern Asians who want work elephants find it much cheaper to capture them in the wild and tame them.

Problems of Captive Breeding. We humans don't like to have s.e.x under the watchful eyes of others; some potentially valuable animal species don't like to, either. That's what derailed attempts to domesticate cheetahs, the swiftest of all land animals, despite our strong motivation to do so for thousands of years.

As I already mentioned, tame cheetahs were prized by ancient Egyptians and a.s.syrians and modern Indians as hunting animals infinitely superior to dogs. One Mogul emperor of India kept a stable of a thousand cheetahs. But despite those large investments that many wealthy princes made, all of their cheetahs were tamed ones caught in the wild. The princes' efforts to breed cheetahs in captivity failed, and not until 1960 did even biologists in modern zoos achieve their first successful cheetah birth. In the wild, several cheetah brothers chase a female for several days, and that rough courts.h.i.+p over large distances seems to be required to get the female to ovulate or to become s.e.xually receptive. Cheetahs usually refuse to carry out that elaborate courts.h.i.+p ritual inside a cage.

A similar problem has frustrated schemes to breed the vicuna, an Andean wild camel whose wool is prized as the finest and lightest of any animal's. The ancient Incas obtained vicuna wool by driving wild vicunas into corrals, shearing them, and then releasing them alive. Modern merchants wanting this luxury wool have had to resort either to this same method or simply to killing wild vicunas. Despite strong incentives of money and prestige, all attempts to breed vicunas' for wool production in captivity have failed, for reasons that include vicunas' long and elaborate courts.h.i.+p ritual before mating, a ritual inhibited in captivity; male vicunas' fierce intolerance of each other; and their requirement for both a year-round feeding territory and a separate year-round sleeping territory.

Nasty Disposition. Naturally, almost any mammal species that is sufficiently large is capable of killing a human. People have been killed by pigs, horses, camels, and cattle. Nevertheless, some large animals have much nastier dispositions and are more incurably dangerous than are others. Tendencies to kill humans have disqualified many otherwise seemingly ideal candidates for domestication.

One obvious example is the grizzly bear. Bear meat is an expensive delicacy, grizzlies weigh up to 1,700 pounds, they are mainly vegetarians (though also formidable hunters), their vegetable diet is very broad, they thrive on human garbage (thereby creating big problems in Yellowstone and Glacier National Parks), and they grow relatively fast. If they would behave themselves in captivity, grizzlies would be a fabulous meat production animal. The Ainu people of j.a.pan made the experiment by routinely rearing grizzly cubs as part of a ritual. For understandable reasons, though, the Ainu found it prudent to kill and eat the cubs at the age of one year. Keeping grizzly bears for longer would be suicidal; I am not aware of any adult that has been tamed.

Another otherwise suitable candidate that disqualifies itself for equally obvious reasons is the African buffalo. It grows quickly up to a weight of a ton and lives in herds that have a well-developed dominance hierarchy, a trait whose virtues will be discussed below. But the African buffalo is considered the most dangerous and unpredictable large mammal of Africa. Anyone insane enough to try to domesticate it either died in the effort or was forced to kill the buffalo before it got too big and nasty. Similarly, hippos, as four-ton vegetarians, would be great barnyard animals if they weren't so dangerous. They kill more people each year than do any other African mammals, including even lions.

Few people would be surprised at the disqualification of those notoriously ferocious candidates. But there are other candidates whose dangers are not so well known. For instance, the eight species of wild equids (horses and their relatives) vary greatly in disposition, even though all eight are genetically so close to each other that they will interbreed and produce healthy (though usually sterile) offspring. Two of them, the horse and the North African a.s.s (ancestor of the donkey), were successfully domesticated. Closely related to the North African a.s.s is the Asiatic a.s.s, also known as the onager. Since its homeland includes the Fertile Crescent, the cradle of Western civilization and animal domestication, ancient peoples must have experimented extensively with onagers. We know from Sumerian and later depictions that onagers were regularly hunted, as well as captured and hybridized with donkeys and horses. Some ancient depictions of horselike animals used for riding or for pulling carts may refer to onagers. However, all writers about them, from Romans to modern zookeepers, decry their irascible temper and their nasty habit of biting people. As a result, although similar in other respects to ancestral donkeys, onagers have never been domesticated.

Africa's four species of zebras are even worse. Efforts at domestication went as far as. .h.i.tching them to carts: they were tried out as draft animals in 19th-century South Africa, and the eccentric Lord Walter Rothschild drove through the streets of London in a carriage pulled by zebras. Alas, zebras become impossibly dangerous as they grow older. (That's not to deny that many individual horses are also nasty, but zebras and onagers are much more uniformly so.) Zebras have the unpleasant habit of biting a person and not letting go. They thereby injure even more American zookeepers each year than do tigers! Zebras are also virtually impossible to la.s.so with a rope-even for cowboys who win rodeo champions.h.i.+ps by la.s.soing horses-because of their unfailing ability to watch the rope noose fly toward them and then to duck their head out of the way.

Hence it has rarely (if ever) been possible to saddle or ride a zebra, and South Africans' enthusiasm for their domestication waned. Unpredictably aggressive behavior on the part of a large and potentially dangerous mammal is also part of the reason why the initially so promising modern experiments in domesticating elk and eland have not been more successful.

Tendency to Panic. Big mammalian herbivore species react to danger from predators or humans in different ways. Some species are nervous, fast, and programmed for instant flight when they perceive a threat. Other species are slower, less nervous, seek protection in herds, stand their ground when threatened, and don't run until necessary. Most species of deer and antelope (with the conspicuous exception of reindeer) are of the former type, while sheep and goats are of the latter.

Naturally, the nervous species are difficult to keep in captivity. If put into an enclosure, they are likely to panic, and either die of shock or batter themselves to death against the fence in their attempts to escape. That's true, for example, of gazelles, which for thousands of years were the most frequently hunted game species in some parts of the Fertile Crescent. There is no mammal species that the first settled peoples of that area had more opportunity to domesticate than gazelles. But no gazelle species has ever been domesticated. Just imagine trying to herd an animal that bolts, blindly bashes itself against walls, can leap up to nearly 30 feet, and can run at a speed of 50 miles per hour!

Social Structure. Almost all species of domesticated large mammals prove to be ones whose wild ancestors share three social characteristics: they live in herds; they maintain a well-developed dominance hierarchy among herd members; and the herds occupy overlapping home ranges rather than mutually exclusive territories. For example, herds of wild horses consist of one stallion, up to half a dozen mares, and their foals. Mare A is dominant over mares B, C, D, and E; mare B is submissive to A but dominant over C, D, and E; C is submissive to B and A but dominant over D and E; and so on. When the herd is on the move, its members maintain a stereotyped order: in the rear, the stallion; in the front, the top-ranking female, followed by her foals in order of age, with the youngest first; and behind her, the other mares in order of rank, each followed by her foals in order of age. In that way, many adults can coexist in the herd without constant fighting and with each knowing its rank.

That social structure is ideal for domestication, because humans in effect take over the dominance hierarchy. Domestic horses of a pack line follow the human leader as they would normally follow the top-ranking female. Herds or packs of sheep, goats, cows, and ancestral dogs (wolves) have a similar hierarchy. As young animals grow up in such a herd, they imprint on the animals that they regularly see nearby. Under wild conditions those are members of their own species, but captive young herd animals also see humans nearby and imprint on humans as well.

Such social animals lend themselves to herding. Since they are tolerant of each other, they can be bunched up. Since they instinctively follow a dominant leader and will imprint on humans as that leader, they can readily be driven by a shepherd or sheepdog. Herd animals do well when penned in crowded conditions, because they are accustomed to living in densely packed groups in the wild.

In contrast, members of most solitary territorial animal species cannot be herded. They do not tolerate each other, they do not imprint on humans, and they are not instinctively submissive. Who ever saw a line of cats (solitary and territorial in the wild) following a human or allowing themselves to be herded by a human? Every cat lover knows that cats are not submissive to humans in the way dogs instinctively are. Cats and ferrets are the sole territorial mammal species that were domesticated, because our motive for doing so was not to herd them in large groups raised for food but to keep them as solitary hunters or pets.

While most solitary territorial species thus haven't been domesticated, it's not conversely the case that most herd species can be domesticated. Most can't, for one of several additional reasons.

First, herds of many species don't have overlapping home ranges but instead maintain exclusive territories against other herds. It's no more possible to pen two such herds together than to pen two males of a solitary species.

Second, many species that live in herds for part of the year are territorial in the breeding season, when they fight and do not tolerate each other's presence. That's true of most deer and antelope species (again with the exception of reindeer), and it's one of the main factors that has disqualified all the social antelope species for which Africa is famous from being domesticated. While one's first a.s.sociation to African antelope is "vast dense herds spreading across the horizon," in fact the males of those herds s.p.a.ce themselves into territories and fight fiercely with each other when breeding. Hence those antelope cannot be maintained in crowded enclosures in captivity, as can sheep or goats or cattle. Territorial behavior similarly combines with a fierce disposition and a slow growth rate to banish rhinos from the farmyard.

Finally, many herd species, including again most deer and antelope, do not have a well-defined dominance hierarchy and are not instinctively prepared to become imprinted on a dominant leader (hence to become misimprinted on humans). As a result, though many deer and antelope species have been tamed (think of all those true Bambi stories), one never sees such tame deer and antelope driven in herds like sheep. That problem also derailed domestication of North American bighorn sheep, which belong to the same genus as Asiatic mouflon sheep, ancestor of our domestic sheep. Bighorn sheep are suitable to us and similar to mouflons in most respects except a crucial one: they lack the mouflon's stereotypical behavior whereby some individuals behave submissively toward other individuals whose dominance they acknowledge.

LET'S NOW RETURN to the problem I posed at the outset of this chapter. Initially, one of the most puzzling features of animal domestication is the seeming arbitrariness with which some species have been domesticated while their close relatives have not. It turns out that all but a few candidates for domestication have been eliminated by the to the problem I posed at the outset of this chapter. Initially, one of the most puzzling features of animal domestication is the seeming arbitrariness with which some species have been domesticated while their close relatives have not. It turns out that all but a few candidates for domestication have been eliminated by the Anna Karenina Anna Karenina principle. Humans and most animal species make an unhappy marriage, for one or more of many possible reasons: the animal's diet, growth rate, mating habits, disposition, tendency to panic, and several distinct features of social organization. Only a small percentage of wild mammal species ended up in happy marriages with humans, by virtue of compatibility on all those separate counts. principle. Humans and most animal species make an unhappy marriage, for one or more of many possible reasons: the animal's diet, growth rate, mating habits, disposition, tendency to panic, and several distinct features of social organization. Only a small percentage of wild mammal species ended up in happy marriages with humans, by virtue of compatibility on all those separate counts.

Eurasian peoples happened to inherit many more species of domesticable large wild mammalian herbivores than did peoples of the other continents. That outcome, with all of its momentous advantages for Eurasian societies, stemmed from three basic facts of mammalian geography, history, and biology. First, Eurasia, befitting its large area and ecological diversity, started out with the most candidates. Second, Australia and the Americas, but not Eurasia or Africa, lost most of their candidates in a ma.s.sive wave of late-Pleistocene extinctions-possibly because the mammals of the former continents had the misfortune to be first exposed to humans suddenly and late in our evolutionary history, when our hunting skills were already highly developed. Finally, a higher percentage of the surviving candidates proved suitable for domestication on Eurasia than on the other continents. An examination of the candidates that were never domesticated, such as Africa's big herd-forming mammals, reveals particular reasons that disqualified each of them. Thus, Tolstoy would have approved of the insight offered in another context by an earlier author, Saint Matthew: "Many are called, but few are chosen."

CHAPTER 10

s.p.a.cIOUS SKIES AND TILTED AXES

ON THE MAP OF THE WORLD ON CHAPTER 10 177 ( 177 (FIGURE 10.1), compare the shapes and orientations of the continents. You'll be struck by an obvious difference. The Americas span a much greater distance north-south (9,000 miles) than east-west: only 3,000 miles at the widest, narrowing to a mere 40 miles at the Isthmus of Panama. That is, the major axis of the Americas is north-south. The same is also true, though to a less extreme degree, for Africa. In contrast, the major axis of Eurasia is east-west. What effect, if any, did those differences in the orientation of the continents' axes have on human history? 10.1), compare the shapes and orientations of the continents. You'll be struck by an obvious difference. The Americas span a much greater distance north-south (9,000 miles) than east-west: only 3,000 miles at the widest, narrowing to a mere 40 miles at the Isthmus of Panama. That is, the major axis of the Americas is north-south. The same is also true, though to a less extreme degree, for Africa. In contrast, the major axis of Eurasia is east-west. What effect, if any, did those differences in the orientation of the continents' axes have on human history?

This chapter will be about what I see as their enormous, sometimes tragic, consequences. Axis orientations affected the rate of spread of crops and livestock, and possibly also of writing, wheels, and other inventions. That basic feature of geography thereby contributed heavily to the very different experiences of Native Americans, Africans, and Eurasians in the last 500 years.

FOOD PRODUCTION'S SPREAD proves as crucial to understanding geographic differences in the rise of guns, germs, and steel as did its origins, which we considered in the preceding chapters. That's because, as we saw in Chapter 5, there were no more than nine areas of the globe, perhaps as few as five, where food production arose independently. Yet, already in prehistoric times, food production became established in many other regions besides those few areas of origins. All those other areas became food producing as a result of the spread of crops, livestock, and knowledge of how to grow them and, in some cases, as a result of migrations of farmers and herders themselves. proves as crucial to understanding geographic differences in the rise of guns, germs, and steel as did its origins, which we considered in the preceding chapters. That's because, as we saw in Chapter 5, there were no more than nine areas of the globe, perhaps as few as five, where food production arose independently. Yet, already in prehistoric times, food production became established in many other regions besides those few areas of origins. All those other areas became food producing as a result of the spread of crops, livestock, and knowledge of how to grow them and, in some cases, as a result of migrations of farmers and herders themselves.

The main such spreads of food production were from Southwest Asia to Europe, Egypt and North Africa, Ethiopia, Central Asia, and the Indus Valley; from the Sahel and West Africa to East and South Africa; from China to tropical Southeast Asia, the Philippines, Indonesia, Korea, and j.a.pan; and from Mesoamerica to North America. Moreover, food production even in its areas of origin became enriched by the addition of crops, livestock, and techniques from other areas of origin.

Just as some regions proved much more suitable than others for the origins of food production, the ease of its spread also varied greatly around the world. Some areas that are ecologically very suitable for food production never acquired it in prehistoric times at all, even though areas of prehistoric food production existed nearby. The most conspicuous such examples are the failure of both farming and herding to reach Native American California from the U.S. Southwest or to reach Australia from New Guinea and Indonesia, and the failure of farming to spread from South Africa's Natal Province to South Africa's Cape. Even among all those areas where food production did spread in the prehistoric era, the rates and dates of spread varied considerably. At the one extreme was its rapid spread along east-west axes: from Southwest Asia both west to Europe and Egypt and east to the Indus Valley (at an average rate of about 0.7 miles per year); and from the Philippines east to Polynesia (at 3.2 miles per year). At the opposite extreme was its slow spread along north-south axes: at less than 0.5 miles per year, from Mexico northward to the U.S. Southwest; at less than 0.3 miles per year, for corn and beans from Mexico northward to become productive in the eastern United States around A.D. A.D. 900; and at 0.2 miles per year, for the llama from Peru north to Ecuador. These differences could be even greater if corn was not domesticated in Mexico as late as 3500 900; and at 0.2 miles per year, for the llama from Peru north to Ecuador. These differences could be even greater if corn was not domesticated in Mexico as late as 3500 B.C. B.C., as I a.s.sumed conservatively for these calculations, and as some archaeologists now a.s.sume, but if it was instead domesticated considerably earlier, as most archaeologists used to a.s.sume (and many still do).

There were also great differences in the completeness with which suites of crops and livestock spread, again implying stronger or weaker barriers to their spreading. For instance, while most of Southwest Asia's founder crops and livestock did spread west to Europe and east to the Indus Valley, neither of the Andes' domestic mammals (the llama / alpaca and the guinea pig) ever reached Mesoamerica in pre-Columbian times. That astonis.h.i.+ng failure cries out for explanation. After all, Mesoamerica did develop dense farming populations and complex societies, so there can be no doubt that Andean domestic animals (if they had been available) would have been valuable for food, transport, and wool. Except for dogs, Mesoamerica was utterly without indigenous mammals to fill those needs. Some South American crops nevertheless did succeed in reaching Mesoamerica, such as manioc, sweet potatoes, and peanuts. What selective barrier let those crops through but screened out llamas and guinea pigs?