Jared Diamond - Guns, Germs & Steel

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since the various dates hardly differ within the experimental error of the radiocarbon method.
At the Pleistocene times when Australia and New Guinea were initially occupied, the Asian continent extended eastward to incorporate the modern islands of Borneo, Java, and Bali, nearly 1,000 miles nearer to Australia and New Guinea than Southeast Asia's present margin. However, at least eight channels up to 50 miles wide still remained to be crossed in getting from Borneo or Bali to Pleistocene Greater Australia. Forty thousand years ago, those crossings may have been achieved by bamboo rafts, low-tech but seaworthy watercraft still in use in coastal South China today. The crossings must nevertheless have been difficult, because after that initial landfall by 40,000 years ago the archaeological record provides no compelling evidence of further human arrivals in Greater Australia from Asia for tens of thousands of years. Not until within the last few thousand years do we encounter the next firm evidence, in the form of the appearance of Asian-derived pigs in New Guinea and Asian-derived dogs in Australia.
Thus, the human societies of Australia and New Guinea developed in substantial isolation from the Asian societies that founded them. That isolation is reflected in languages spoken today. After all those millennia of isolation, neither modern Aboriginal Australian languages nor the major group of modern New Guinea languages (the so-called Papuan languages) exhibit any clear relationships with any modern Asian languages.
The isolation is also reflected in genes and physical anthropology. Genetic studies suggest that Aboriginal Australians and New Guinea high-landers are somewhat more similar to modern Asians than to peoples of other continents, but the relationship is not a close one. In skeletons and physical appearance, Aboriginal Australians and New Guineans are also distinct from most Southeast Asian populations, as becomes obvious if one compares photos of Australians or New Guineans with those of Indonesians or Chinese. Part of the reason for all these differences is that the initial Asian colonists of Greater Australia have had a long time in which to diverge from their stay-at-home Asian cousins, with only limited genetic exchanges during most of that time. But probably a more important reason is that the original Southeast Asian stock from which the colonists of
reater Australia were derived has by now been largely replaced by other Asians expanding out of China.

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Aboriginal Australians and New Gumeans have also diverged genetically, physically, and linguistically from each other. For instance, among the major (genetically determined) human blood groups, groups B of the so-called ABO system and S of the MNS system occur in New Guinea as well as in most of the rest of the world, but both are virtually absent in Australia. The tightly coiled hair of most New Guineans contrasts with the straight or wavy hair of most Australians. Australian languages and New Guinea's Papuan languages are unrelated not only to Asian languages but also to each other, except for some spread of vocabulary in both directions across Torres Strait.
All that divergence of Australians and New Guineans from each other reflects lengthy isolation in very different environments. Since the rise of the Arafura Sea finally separated Australia and New Guinea from each other around 10,000 years ago, gene exchange has been limited to tenuous contact via the chain of Torres Strait islands. That has allowed the populations of the two hemi-continents to adapt to their own environments. While the savannas and mangroves of coastal southern New Guinea are fairly similar to those of northern Australia, other habitats of the hemi-continents differ in almost all major respects.
Here are some of the differences. New Guinea lies nearly on the equator, while Australia extends far into the temperate zones, reaching almost 40 degrees south of the equator. New Guinea is mountainous and extremely rugged, rising to 16,500 feet and with glaciers capping the highest peaks, while Australia is mostly low and flat—94 percent of its area lies below 2,000 feet of elevation. New Guinea is one of the wettest areas on Earth, Australia one of the driest. Most of New Guinea receives over 100 inches of rain annually, and much of the highlands receives over 200 inches, while most of Australia receives less than 20 inches. New Guinea's equatorial climate varies only modestly from season to season and year to year, but Australia's climate is highly seasonal and varies from year to year far more than that of any other continent. As a result, New Guinea is laced with permanent large rivers, while Australia's permanently flowing rivers are confined in most years to eastern Australia, and even Australia's largest river system (the Murray-Darling) has ceased flowing for months during droughts. Must of New Guinea's land area is clothed in dense rain forest, while most of Australia's supports only desert and open dry woodland.
New Guinea is covered with young fertile soil, as a consequence of volcanic activity, glaciers repeatedly advancing and retreating and scouring

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the highlands, and mountain streams carrying huge quantities of silt to the lowlands. In contrast, Australia has by far the oldest, most infertile, most nutrient-leached soils of any continent, because of Australia's little volcanic activity and its lack of high mountains and glaciers. Despite having only one-tenth of Australia's area, New Guinea is home to approximately as many mammal and bird species as is Australia—a result of New Guinea's equatorial location, much higher rainfall, much greater range of elevations, and greater fertility. All of those environmental differences influenced the two hemi-continents' very disparate cultural histories, which we shall now consider.
theearliest and most intensive food production, and the densest populations, of Greater Australia arose in the highland valleys of New Guinea at altitudes between 4,000 and 9,000 feet above sea level. Archaeological excavations uncovered complex systems of drainage ditches dating back to 9,000 years ago and becoming extensive by 6,000 years ago, as well as terraces serving to retain soil moisture in drier areas. The ditch systems were similar to those still used today in the highlands to drain swampy areas for use as gardens. By around 5,000 years ago, pollen analyses testify to widespread deforestation of highland valleys, suggesting forest clearance for agriculture.
Today, the staple crops of highland agriculture are the recently introduced sweet potato, along with taro, bananas, yams, sugarcane, edible grass stems, and several leafy vegetables. Because taro, bananas, and yams are native to Southeast Asia, an undoubted site of plant domestication, it used to be assumed that New Guinea highland crops other than sweet potatoes arrived from Asia. However, it was eventually realized that the wild ancestors of sugarcane, the leafy vegetables, and the edible grass stems are New Guinea species, that the particular types of bananas grown in New Guinea have New Guinea rather than Asian wild ancestors, and that taro and some yams are native to New Guinea as well as to Asia. If New Guinea agriculture had really had Asian origins, one might have expected to find highland crops derived unequivocally from Asia, but there are none. For those reasons it is now generally acknowledged that agriculture arose indigenously in the New Guinea highlands by domestication of New Guinea wild plant species.
New Guinea thus joins the Fertile Crescent, China, and a few other

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regions as one of the world's centers of independent origins of plant domestication. No remains of the crops actually being grown in the highlands 6,000 years ago have been preserved in archaeological sites. However, that is not surprising, because modern highland staple crops are plant species that do not leave archaeologically visible residues except under exceptional conditions. Hence it seems likely that some of them were also the founding crops of highland agriculture, especially as the ancient drainage systems preserved are so similar to the modern drainage systems used for growing taro.
The three unequivocally foreign elements in New Guinea highland food production as seen by the first European explorers were chickens, pigs, and sweet potatoes. Chickens and pigs were domesticated in Southeast Asia and introduced around 3,600 years ago to New Guinea and most other Pacific islands by Austronesians, a people of ultimately South Chinese origin whom we shall discuss in Chapter 17. (Pigs may have arrived earlier.) As for the sweet potato, native to South America, it apparently reached New Guinea only within the last few centuries, following its introduction to the Philippines by Spaniards. Once established in New Guinea, the sweet potato overtook taro as the highland's leading crop, because of its shorter time required to reach maturity, higher yields per acre, and greater tolerance of poor soil conditions.
The development of New Guinea highland agriculture must have triggered a big population explosion thousands of years ago, because the highlands could have supported only very low population densities of hunter-gatherers after New Guinea's original megafauna of giant marsupials had been exterminated. The arrival of the sweet potato triggered a further explosion in recent centuries. When Europeans first flew over the highlands in the 1930s, they were astonished to see below them a landscape similar to Holland's. Broad valleys were completely deforested and dotted with villages, and drained and fenced fields for intensive food production covered entire valley floors. That landscape testifies to the population densities achieved in the highlands by farmers with stone tools.
Steep terrain, persistent cloud cover, malaria, and risk of drought at lower elevations confine New Guinea highland agriculture to elevations above about 4,000 feet. In effect, the New Guinea highlands are an island of dense farming populations thrust up into the sky and surrounded below by a sea of clouds. Lowland New Guineans on the seacoast and rivers are villagers depending heavily on fish, while those on dry ground away from