Guns, Germs & Steel

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 m 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

174 ' GUNS, GERMS, AND STEEL
all the social antelope species for which Africa is famous from being domesticated. While one's first association to African antelope is 'vast dense herds spreading across the horizon,' in fact the males of those herds space 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 misim-printed 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 chapt Initially, one of the most puzzling features of animal domestication is seeming arbitrariness with which some species have been domesticat while their close relatives have not. It turns out that all but a few candii| dates for domestication have been eliminated by the Anna Karenina princi4| pie. Humans and most animal species make an unhappy marriage, for onfrl or more of many possible reasons: the animal's diet, growth rate, matiftp| habits, disposition, tendency to panic, and several distinct features social organization. Only a small percentage of wild mammal sj ended up in happy marriages with humans, by virtue of compatibility' all those separate counts.
Eurasian peoples happened to inherit many more species of don ticable large wild mammalian herbivores than did peoples of the continents. That outcome, with all of its momentous advantages for asian societies, stemmed from three basic facts of mammalian geograf history, and biology. First, Eurasia, befitting its large area and ecolo-

ZEBRASAND UNHAPPY MARRIAGES • I 7 5
gy started out with the most candidates. Second, Australia and the but not Eurasia or Africa, lost most of their candidates in a Americas) ^i'
sive wave of late-Pleistocene extinctions—possibly because the mam-Is of the former continents had the misfortune to be first exposed to h mans suddenly and late in our evolutionary history, when our hunting skills were already highly developed. Finally, a higher percentage of the rviving 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.'

CHAPTER10
spacious skies and tilted axes

ON THE MAP OF THE WORLD ON PAGE 177 (FIGURE 10.) compare the shapes and orientations of the continents. You'll 1 struck by an obvious difference. The Americas span a much greater tance north-south (9,000 miles) than east-west: only 3,000 miles at widest, narrowing to a mere 40 miles at the Isthmus of Panama. That the major axis of the Americas is north-south. The same is also though to a less extreme degree, for Africa. In contrast, the major axis* Eurasia is east-west. What effect, if any, did those differences in the ork tation of the continents' axes have on human history?
This chapter will be about what I see as their enormous, son tragic, consequences. Axis orientations affected the rate of spread of and livestock, and possibly also of writing, wheels, and other inver That basic feature of geography thereby contributed heavily to the different experiences of Native Americans, Africans, and Eurasians in.) last 500 years.
food production's spread proves as crucial to understar geographic differences in the rise of guns, germs, and steel as did its orgins, which we considered in the preceding chapters. That's because, as

SPACIOUSSKIES AND TILTED AXES • 177

Figure 10.1. Major axes of the continents.
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 Japan; 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

I 7 8 •GUNS,GERMS, AND STEEL
American California from the U.S. Southwest or to reach Australia from New Guinea and Indonesia, and the failure of farming to spread front South Africa's Natal Province to South Africa's Cape. Even among alt those areas where food production did spread in the prehistoric era, the rates and dates of spread varied considerably. At the one extreme was itt-l rapid spread along east-west axes: from Southwest Asia both west Europe and Egypt and east to the Indus Valley (at an average rate of aboqff 0.7 miles per year); and from the Philippines east to Polynesia (at 3.21 per year). At the opposite extreme was its slow spread along nor axes: at less than 0.5 miles per year, from Mexico northward to the U.1 Southwest; at less than 0.3 miles per year, for corn and beans from ] northward to become productive in the eastern United States around,