303 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 304 ' GUNS, GERMS, AND STEEL 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 YALI'SPEOPLE • 305 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 non-literate, 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 popu- 3 O 6 •GUNS,GERMS, AND STEEL lations. 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
