Diffusion, Trade, and Disease Theme Analysis

As we'll see, food production was indirectly a prerequisite for the development of guns, germs, and steel. Hence geographic variation in whether, or when, the peoples of different continents became farmers and herders explains to a large extent their subsequent contrasting fates.

The same pattern of an abrupt start of food production dependent on domesticates from elsewhere, and an abrupt and massive population replacement, seems to have repeated itself in many areas in the prehistoric era. In the absence of written records, the evidence of those prehistoric replacements must be sought in the archaeological record or inferred from linguistic evidence.

Plant domestication is not a matter of hunter-gatherers domesticating a single plant and otherwise carrying on unchanged with their nomadic lifestyle. Suppose that North American wild apples really would have evolved into a terrific crop if only Indian hunter-gatherers had settled down and cultivated them. But nomadic hunter-gatherers would not throw over their traditional way of life, settle in villages, and start tending apple orchards unless many other domesticable wild plants and animals were available to make a sedentary food-producing existence competitive with a hunting-gathering existence.

Why was the spread of crops from the Fertile Crescent so rapid? The answer depends partly on that east-west axis of Eurasia with which I opened this chapter. Localities distributed east and west of each other at the same latitude share exactly the same day length and its seasonal variations. To a lesser degree, they also tend to share similar diseases, regimes of temperature and rainfall, and habitats or biomes (types of vegetation).

The earliest wheels were parts of ox-drawn carts used to transport agricultural produce. Early writing was restricted to elites supported by food-producing peasants, and it served purposes of economically and socially complex food-producing societies (such as royal propaganda, goods inventories, and bureaucratic record keeping). In general, societies that engaged in intense exchanges of crops, livestock, and technologies related to food production were more likely to become involved in other exchanges as well.

There is no doubt that Europeans developed a big advantage in weaponry, technology and political organization over most of the non-European peoples that they conquered. But that advantage alone doesn't fully explain how initially so few European immigrants came to supplant so much of the native population of the Americas and some other parts of the world. That might not have happened without Europe's sinister gift to other continents—the germs evolving from Eurasians' long intimacy with domestic animals.

Given enough time, the societies lacking writing might also have eventually developed it on their own. Had they been located nearer to Sumer, Mexico, and China, they might instead have acquired writing or the idea of writing from those centers, just as did India, the Maya, and most other societies with writing. But they were too far from the first centers of writing to have acquired it before modern times.

This cultural barrier at Torres Strait is astonishing only because we may mislead ourselves into picturing a full-fledged New Guinea society with intensive agriculture and pigs 10 miles off the Australian coast. In reality, Cape York Aborigines never saw a mainland New Guinean. Instead, there was trade between New Guinea and the islands nearest New Guinea, then between those islands and Mabuiag Island halfway down the strait, then between Mabuiag Island and Badu Island farther down the strait, then between Badu Island and Muralug Island, and finally between Muralug and Cape York.

Europeans have never learned to survive in Australia or New Guinea without their inherited Eurasian technology. Robert Burke and William Wills were smart enough to write, but not smart enough to survive in Australian desert regions where Aborigines were living.

Many readers may already be protesting: don't stereotype people by classifying them into arbitrary "races"! Yes, I acknowledge that each of these so-called major groups is very diverse. To lump people as different as Zulus, Somalis, and Ibos under the single heading of "blacks" ignores the differences between them. We ignore equally big differences when we lump Africa's Egyptians and Berbers with each other and with Europe's Swedes under the single heading of "whites." In addition, the divisions between blacks, whites, and the other major groups are arbitrary, because each such group shades into others: all human groups on Earth have mated with humans of every other group that they encountered.

But China's connectedness eventually became a disadvantage, because a decision by one despot could and repeatedly did halt innovation. In contrast, Europe's geographic balkanization resulted in dozens or hundreds of independent, competing statelets and centers of innovation. If one state did not pursue some particular innovation, another did, forcing neighboring states to do likewise or else be conquered or left economically behind. Europe's barriers were sufficient to prevent political unification, but insufficient to halt the spread of technology and ideas. There has never been one despot who could turn off the tap for all of Europe, as of China.