Guns, Germs, and Steel

by Jared Diamond

  The isolation is also reflected in genes and physical anthropology. Genetic studies suggest that Aboriginal Australians and New Guinea highlanders 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 Greater Australia were derived has by now been largely replaced by other Asians expanding out of China.

  Aboriginal Australians and New Guineans 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. Most 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 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.

  THE EARLIEST 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 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 the coast and rivers subsist at low densities by slash-and-burn agriculture based on bananas and yams, supplemented by hunting and gathering. In contrast, lowland New Guinea swamp dwellers live as nomadic hunter-gatherers dependent on the starchy pith of wild sago palms, which are very productive and yield three times more calories per hour of work than does gardening. New Guinea swamps thus provide a clear instance of an environment where people remained hunter-gatherers because farming could not compete with the hunting-gathering lifestyle.

  The sago eaters persisting in lowland swamps exemplify the nomadic hunter-gatherer band organization that must formerly have characterized all New Guineans. For all the reasons that we discussed in Chapters 13 and 14, the farmers and the fishing peoples were the ones to develop more-complex technology, societies, and political organization. They live in permanent villages and tribal societies, often led by a big-man. Some of them construct large, elaborately decorated, ceremonial houses. Their great art, in the form of wooden statues and masks, is prized in museums around the world.

  NEW GUINEA THUS became the part of Greater Australia with the most-advanced technology, social and political organization, and art. However, from an urban American or European perspective, New Guinea still rates as “primitive” rather than “advanced.” Why did New Guineans continue to use stone tools instead of developing metal tools, remain nonliterate, and fail to organize themselves into chiefdoms and states? It turns out that New Guinea had several biological and geographic strikes against it.

  First, although indigenous food production did arise in the New Guinea highlands, we saw in Chapter 8 that it yielded little protein. The dietary staples were low-protein root crops, and production of the sole domesticated animal species (pigs and chickens) was too low to contribute much to people’s protein budgets. Since neither pigs nor chickens can be harnessed to pull carts, highlanders remained without sources of power other than human muscle power, and also failed to evolve epidemic diseases to repel the eventual European invaders.

  A second restriction on the size of highland populations was the limited available area: the New Guinea highlands have only a few broad valleys, notably the Wahgi and Baliem Valleys, capable of supporting dense populations. Still a third limitation was the reality that the mid-montane zone between 4,000 and 9,000 feet was the sole altitudinal zone in New Guinea suitable for intensive food production. There was no food production at all in New Guinea alpine habitats above 9,000 feet, little on the hillslopes between 4,000 and 1,000 feet, and only low-density slash-and-burn agriculture in the lowlands. Thus, large-scale economic exchanges of food, between communities at different altitudes specializing in different types of food production, never developed in New Guinea. Such exchanges in the Andes, Alps, and Himalayas not only increased population densities in those areas, by providing people at all altitudes with a more balanced diet, but also promoted regional economic and political integration.

  For all these reasons, the population of traditional New Guinea never exceeded 1,000,000 until European colonial governments brought Western medicine and the end of intertribal warfare. Of the approximately nine world centers of agricultural origins that we discussed in Chapter 5, New Guinea remained the one with by far the smallest population. With a mere 1,000,000 people, New Guinea could not develop the technology, writing, and political systems that arose among populations of tens of millions in China, the Fertile Crescent, the Andes, and Mesoamerica.

  New Guinea’s population is not only small in aggregate, but also fragmented into thousands of micropopulations by the rugged terrain: swamps in much of the lowlands, steep-sided ridges and narrow canyons alternating with each other in the highlands, and dense jungle swathing both the lowlands and the highlands. When I am engaged in biological exploration in New Guinea, with teams of New Guineans as field assistants, I consider excellent progress to be three miles per day even if we are traveling over existing trails. Most highlanders in traditional New Guinea never went more than 10 miles from home in the course of their lives.

  Those difficulties of terrain, combined with the state of intermittent warfare that characterized relations between New Guinea bands or villages, account for traditional New Guinea’s linguistic, cultural, and political fragmentation. New Guinea has by far the highest concentration of languages in the world: 1,000 out of the world’s 6,000 languages, crammed into an area only slightly larger than that of Texas, and divided into dozens of language families and isolated languages as different from each other as English is from Chinese. Nearly half of all New Guinea languages have fewer than 500 speakers, and even the largest language groups (still with a mere 100,000 speakers) were politically fragmented into hundreds of villages, fighting as fiercely with each other as with speakers of other languages. Each of those microsocieties alone was far too small to support chiefs and craft specialists, or to develop metallurgy and writing.

  Besides a small and fragmented population, the other limitation on development in New Guinea was geographic isolation, restricting the inflow of technology and ideas from elsewhere. New Guinea’s three neighbors were all separated from New Guinea by water gaps, and until a few thousand years ago they were all even less advanced than New Guinea (especially the New Guinea highlands) in technology and food production. Of those three neighbors, Aboriginal Australians remained hunter-gatherers with almost nothing to offer New Guineans that New Guineans did not already possess. New Guinea’s second neighbor was the much smaller islands of the Bismarck and the Solomon Archipelagoes to the east. That left, as New Guinea’s third neighbor, the islands of eastern Indonesia. But that area, too, remained a cultural backwater occupied by hunter-gatherers for most of its history. There is no item that can be identified as having reached New Guinea via Indonesia, after the initial colonization of New Guinea over 40,000 years ago, until the time of the Austronesian expansion around 1600 B.C.

  With that expansion, Indonesia became occupied by food producers of Asian origins, with domestic animals, with agriculture and technology at least as complex as New Guinea’s, and with navigational skills that served as a much more efficient conduit from Asia to New Guinea. Austronesians settled on islands west and north and east of New Guinea, and in the far west and on the north and southeast coasts of New Guinea itself. Austronesians introduced pottery, chickens, and probably dogs and pigs to New Guinea. (Early archaeological surveys claimed pig bones in the New Guinea highlands by 4000 B.C., but those claims have not been confirmed.) For at least the last thousand years, trade connected New Guinea to the technologically much more advanced societies of Java and China. In return for exporting bird of paradise plumes and spices, New Guineans received Southeast Asian goods, including even such luxury items as Dong Son bronze drums and Chinese porcelain.

  With time, the Austronesian expansion would surely have had more impact on New Guinea. Western New Guinea would eventually have been incorporated politically into the sultanates of eastern Indonesia, and metal tools might have spread through eastern Indonesia to New Guinea. But—that hadn’t happened by A.D. 1511, the year the Portuguese arrived in the Moluccas and truncated Indonesia’s separate train of developments. When Europeans reached New Guinea soon thereafter, its inhabitants were still living in bands or in fiercely independent little villages, and still using stone tools.

  WHILE THE NEW Guinea hemi-continent of Greater Australia thus developed both animal husbandry and agriculture, the Australian hemi-continent developed neither. During the Ice Ages Australia had supported even more big marsupials than New Guinea, including diprotodonts (the marsupial equivalent of cows and rhinoceroses), giant kangaroos, and giant wombats. But all those marsupial candidates for animal husbandry disappeared in the wave of extinctions (or exterminations) that accompanied human colonization of Australia. That left Australia, like New Guinea, with no domesticable native mammals. The sole foreign domesticated mammal adopted in Australia was the dog, which arrived from Asia (presumably in Austronesian canoes) around 1500 B.C. and established itself in the
wild in Australia to become the dingo. Native Australians kept captive dingos as companions, watchdogs, and even as living blankets, giving rise to the expression “five-dog night” to mean a very cold night. But they did not use dingos / dogs for food, as did Polynesians, or for cooperative hunting of wild animals, as did New Guineans.

  Agriculture was another nonstarter in Australia, which is not only the driest continent but also the one with the most infertile soils. In addition, Australia is unique in that the overwhelming influence on climate over most of the continent is an irregular nonannual cycle, the ENSO (acronym for E1 Niño Southern Oscillation), rather than the regular annual cycle of the seasons so familiar in most other parts of the world. Unpredictable severe droughts last for years, punctuated by equally unpredictable torrential rains and floods. Even today, with Eurasian crops and with trucks and railroads to transport produce, food production in Australia remains a risky business. Herds build up in good years, only to be killed off by drought. Any incipient farmers in Aboriginal Australia would have faced similar cycles in their own populations. If in good years they had settled in villages, grown crops, and produced babies, those large populations would have starved and died off in drought years, when the land could support far fewer people.

  The other major obstacle to the development of food production in Australia was the paucity of domesticable wild plants. Even modern European plant geneticists have failed to develop any crop except macadamia nuts from Australia’s native wild flora. The list of the world’s potential prize cereals—the 56 wild grass species with the heaviest grains—includes only two Australian species, both of which rank near the bottom of the list (grain weight only 13 milligrams, compared with a whopping 40 milligrams for the heaviest grains elsewhere in the world). That’s not to say that Australia had no potential crops at all, or that Aboriginal Australians would never have developed indigenous food production. Some plants, such as certain species of yams, taro, and arrowroot, are cultivated in southern New Guinea but also grow wild in northern Australia and were gathered by Aborigines there. As we shall see, Aborigines in the climatically most favorable areas of Australia were evolving in a direction that might have eventuated in food production. But any food production that did arise indigenously in Australia would have been limited by the lack of domesticable animals, the poverty of domesticable plants, and the difficult soils and climate.