this time.
Even for the more recent dates, however, linguistic comparisons are unable to relate the distribution of contemporary languages to the earliest migrations, and we have no way of knowing if there were one or many. And the archaeological evidence is meager. A dig has recovered 39,000-year-old stone tools from the Huon Peninsula, but little else from this earliest period.
A later Papuan migration may have coincided with the last glacial peak, which occurred some 16,000 to 18,000 years ago. After that, as the earth's atmosphere warmed, the seas rose as much as 6 meters above their present level.
The Papuans of 18,000 years ago lived in a New Guinea radically different from the one we find today. Ice sheets covered 2,000 square kilometers of the island and the snow line stood a mere 1,100 meters above sea level. (Today, there is only 6.9 square kilometers of glacier left.) The tree line stood at 1,600 meters below the present one and temperatures averaged 7° Centigrade cooler.
For many millennia after reaching the island, the Papuans expanded within New Guinea and to neighboring islands. Their aboriginal Australian cousins adapted themselves to a radically different ecology. The two gene pools have been isolated from one another for at least 10,000 years, and probably longer.
A linguistic Babel
Linguistic studies show, moreover, that the various Papuan groups have evolved in relative isolation from one another for many thousands of years, partly because of the island's rugged geography but also because each group was typically in a perpetual state of warfare with its neighbors. As a result, New Guinea, with only .01 percent of the earth's population, now contains 15 percent of its known languages.
Estimates of the number of distinct languages spoken by the 2.7 million people of New Guinea vary from a whopping 800 down to about 80, depending on one's definition of what constitutes a distinct language. Some languages in West Papua today are spoken by just a handful of people, and the 1.6 million West Papuans probably speak 250 languages.
In trying to bring order to this linguistic chaos, experts have been forced to divide West Papua's many tongues into at least four distinct phyla or families. (Languages in a phylum share less than 5 percent of their basic vocabulary with the languages in another—and by way of comparison, most of the languages of Europe fall into a single family, the Indo-European phylum.) These are the East Bird's Head phylum, the Cenderawasih Bay phylum, the West Papua phylum (which includes north Halmahera) and the Trans-New Guinea phylum. The last is the most widespread on the island, comprising 84 percent of Papuan speakers and 67 percent of the languages.
As the climate of New Guinea warmed, more ecological zones became suitable for human habitation. Farming may have begun more than 20,000 years ago, but for most West Papuans, hunting and gathering remained the basic source of food for many thousands of years after. A lack of systematic archaeological work leaves us with hypotheses and conjectures for the next stages of human development, but it is likely that agriculture, based on taro as the staple, was already in progress 6,000 years ago, and there is evidence of agriculture in the highlands from 9,000 years ago.
The seafaring Austronesians
The peoples who are known today as Malays, Indonesians, Filipinos and Polynesians share a common ancestry that can be traced back to a handful of hardy seafarers who left the coasts of southern China some 6,000-7,000 years ago. Collectively they are known as Austronesians (older texts call this group "Malayo-Polynesians").
The accepted wisdom had been that the original Austronesians moved down through mainland Southeast Asia and hence to the islands. But contemporary linguistic evidence suggests that this group underwent a gradual expansion, as a result of advancements in agriculture and sailing techniques, with Taiwan as the jumping-off point. From there they voyaged through the Philippines to Indonesia and out across the vast reaches of the Pacific and Indian Oceans.
The Austronesians brought with them a social organization distinguished by what are called bilateral, or non-unilineal, descent—wherein both biological parents are recognized for purposes of affiliation. This contrasts with the unilineal societies of New Guinea and Melanesia which are mostly patrilineal, wherein descent, as in European societies, is recognized through the father. (Or sometimes the mother, but rarely both.)
Austronesian speakers appeared in the islands of Indonesia by about 3,000 B.C. and over the next two millennia, through superior technology and sheer weight of numbers, they gradually displaced the aboriginal populations who then lived here. This seemingly inexorable displacement process never took place in New Guinea. The Papuans were never displaced from New Guinea, it seems, because of the terrain and the existence of stable, well-established groups of agriculturally sophisticated Papuans.
The two groups intermingle
Although the Austronesians never penetrated to the interior of West Papua, they settled and intermixed with Papuans along the coast and on the nearby islands, mingling their genes, but imposing their languages. At about this same time—2,000 B.C.—a major expansion of the Trans-New Guinea phylum of Papuan language speakers also occurred, west from New Guinea to the islands of Timor, Alor and Pantar, where they replaced earlier West Papuan language speakers.
These islands had already been settled by Papuan speakers long before the Austronesian arrival, and there were probably two phases of Papuan settlement here: a first taking place many thousands of years earlier, and a second contemporaneous with the Austronesian arrival.
The second Papuan expansion was perhaps due to an agricultural "revolution" that included the domestication of pigs and tubers in New Guinea by at least 4,000 B.C. The Trans-New Guinea languages, strongly influenced by Austronesian loan words, also expanded into the island's central highlands by about 1500 B.C., wiping out traces of earlier diversity there.
A sweet potato revolution
The introduction of the sweet potato (Ipomoea batatas), ranks among the most crucial factors in New Guinea's evolution. The sweet potato is a New World plant, and it was once thought to have been introduced a few centuries ago by early Portuguese and Spanish navigators. Recently, however, some plant geneticists have said that the plant must have arrived at a much earlier date, perhaps A.D. 500. How it could have gotten there at this time remains a mystery.
Whenever it started, the Ipomoea revolution brought high yields at healthy elevations. Unlike taro, the sweet potato grows well up to 1,600 meters above sea level, allowing its cultivators to settle out of the range of the malarial Anopheles mosquito and exploit the fertile soils of the Central Highlands.
The sweet potato allowed for much more intensive agriculture, which together with healthier conditions, resulted in relatively higher population densities in the highlands. Crucial also was the development of a technically brilliant system of parallel or gridiron irrigation ditches, which allowed for fallow times equal to that of the cropping cycle. Older slash-and-burn techniques used elsewhere on the island require 10-20 years of fallow time between crops, resulting in much lower population densities.
In the southeast corner of West Papua, the Marind-Anim experienced their own agricultural revolution. Beds of earth, surrounded by drainage ditches, were here raised in the swamps and planted with yam and taro alternating with bananas, and areca and sugar palms. These efficient gardens provided food for similarly dense population settlements.
Prehistoric trade
Trade in the eastern islands of the archipelago began long before the common era. Fragrant Timorese sandalwood and Moluccan cloves are mentioned in early Han Chinese texts, and the latter have also been found in Egyptian mummies. In early times
