own specific subsistence economy adapted to a different local ecology: for instance, a mountainous area can support mountain herders, hill farmers, lowland river fishermen, and lowland savannah pastoralists at different elevations and in different habitats.
Ecological factors thus already tell us several reasons why small New Guinea has 5–10 times more languages than does huge Russia, Canada, or China. New Guinea lies within a few degrees of the equator, so its people experience only slight variations in climate. The New Guinea landscape is wet, fertile, and productive. New Guineans don’t move much or at all with seasons or from year to year; they can meet all of their subsistence needs within a small area; and they don’t have to trade except for salt, stone for tools, and luxuries like shells and feathers. New Guinea is rugged and ecologically diverse, with mountains up to 16,500 feet, rivers, lakes, seacoasts, savannahs, and forests. One could object that China and Canada have even higher mountains and offer a larger range of elevations than does New Guinea. But New Guinea’s tropical location means that New Guineans can live year-round and farm at high population densities up to elevations of 8,000 feet, while high elevations in China and Canada are seasonally freezing and support only low human population densities (in Tibet) or no people at all.
In addition to those ecological factors, there are also socio-economic and historical factors contributing to differences in language diversity around the world. One such factor is that hunter-gatherer speech communities consist of fewer individuals but may cover larger areas than farmer speech communities. For instance, Aboriginal Australia was traditionally inhabited entirely by hunter-gatherers occupying an average of 12,000 square miles per language, while neighboring New Guinea supported mostly farmers occupying only 300 square miles per language. Within Indonesian New Guinea, I worked in areas supporting nearby both farmers (in the Central Highlands) and hunter-gatherers (in the Lakes Plains), with about two dozen languages for each lifestyle. The average hunter- gatherer language there had only 388 speakers, while the average farmer language had 18,241 speakers. The main reason for the small speech communities of hunter-gatherers is low food availability, hence low human population densities. Within the same environment, population densities of hunter-gatherers are 10 to 100 times lower than those of farmers, because much less food is available to hunter-gatherers, able to eat only that tiny fraction of wild plant species that is edible, than to farmers, who convert the landscape into gardens and orchards of edible plants.
A second socio-economic factor related to language diversity is political organization: language diversity decreases, and language communities increase in population and in area, with increasing political complexity from bands to states. For instance, the United States today, a large state with a single dominant coast-to-coast language, has a population about 30 times what was the population of the entire world at a time when the world still consisted entirely of hunter-gatherer bands and tribes with thousands of languages. The dominant U.S. language of English has largely replaced the hundreds of different local languages formerly spoken five centuries ago in what is now the national territory of the U.S. when it was divided among Native American bands, tribes, and chiefdoms. Underlying this trend is the fact, discussed in the Prologue, that increasing political complexity becomes necessary as a society increases in population—because a society of a few dozen people can make decisions in a group meeting without a leader, but a society of millions requires leaders and bureaucrats to operate. States expand their own languages at the expense of the languages of conquered and incorporated groups. That language expansion is partly a matter of state policy for the purposes of administration and national unity, and partly a spontaneous matter of individual citizens adopting the national language in order to obtain economic and social opportunities for themselves.
The remaining factor is a historical one whose various outcomes include the just-mentioned decrease in language diversity with increasing political complexity. World regions have repeatedly been swept by “language steamrollers,” in which one group enjoying some advantage of population numbers, food base, or technology exploits that advantage to expand at the expense of neighboring groups, imposing its own language on the region and replacing previous local languages by driving out or killing their speakers or converting them to speaking the invader’s language. The most familiar steamrollers are those associated with expansions of powerful states over stateless peoples. Recent examples have included European expansions replacing native languages of the Americas, the British conquest of Australia replacing Aboriginal Australian languages, and the Russian expansion over the Ural Mountains to the Pacific Ocean replacing native Siberian languages. In the past, as well, there have been historically documented state-driven steamrollers. The Roman Empire’s expansion over the Mediterranean basin and most of Western Europe extinguished Etruscan, Continental Celtic languages, and many other languages. The expansion of the Inca Empire and its predecessors similarly spread the Quechua and Aymara languages over the Andes.
Less familiar to non-linguists are the steamrollers driven by expansions of pre-literate farmers over the lands of hunter-gatherers, and inferred from linguistic and archaeological rather than historical evidence. Well understood ones include the expansions of Bantu and Austronesian farmers, which largely replaced the former languages of hunter-gatherers in subequatorial Africa and Island Southeast Asia respectively. There were also steamrollers in which hunter-gatherers overran other hunter-gatherers, driven by improved technology: e.g., the expansion of the Inuit 1,000 years ago eastwards across the Canadian Arctic, based on technological advances such as dog sleds and kayaks.
A consequence of these several types of historical expansions is that some world regions containing few geographic barriers have repeatedly been overrun by linguistic steamrollers. The immediate result is very low linguistic diversity, because an invading language sweeps away pre-existing linguistic diversity. With time, the invading language differentiates into local dialects and then into separate languages, but all of them still closely related to each other. An early stage in this process is illustrated by the Inuit expansion of 1,000 years ago; all eastern Inuit people from Alaska to Greenland still speak mutually intelligible dialects of a single language. The Roman and Bantu expansions of 2,000 years ago represent a slightly later stage: the various Italic languages (such as French, Spanish, and Romanian) are very similar but no longer mutually intelligible, as is also true of the hundreds of closely related Bantu languages. At a still later stage, the Austronesian expansion that began around 6,000 years ago has by now generated a thousand languages falling into eight branches, but still sufficiently similar that there is no doubt about their relationship.
Contrasting with those easily overrun areas that Johanna Nichols terms “language spread zones” are what she terms “residual zones” or refugia: mountainous and other areas that are difficult for states and other outsiders to overrun, where languages survive and diffentiate for long times, and hence where unique language groups survive. Famous examples are the Caucasus Mountains, with 3 unique language families plus a few recently invaded languages belonging to three other widespread families; northern Australia, to which 26 of Aboriginal Australia’s 27 language families are confined; Indian California, with about 80 languages variously classified into somewhere between 6 and 22 families; and, of course, New Guinea, with its 1,000 languages classified in dozens of families.
We thus have several more reasons why New Guinea leads the world in number of languages and of language families. In addition to the ecological reasons previously mentioned—little seasonal variation, sedentary populations, a productive environment supporting high human population densities, and great ecological diversity supporting many co-existing human groups with different subsistence strategies—we now have some socio- economic and historical factors as well. Those include the facts that traditional New Guinea never developed state government, so there was never a state steamroller to homogenize linguistic diversity; and that, as a result of New Guinea’s highly dissected mountainous terrain, the steamroller probably caused by the spread of Highlands farming (that associated with the so-called Trans–New Guinea language phylum) was unable to eliminate dozens of older New Guinea language phyla.
Traditional multilingualism
Those are the reasons why the modern world inherited 7,000 languages from the traditional world until yesterday, and why language communities of hunter-gatherers and small-scale farmers without state government contained many fewer speakers than do modern state societies. What about bilingualism and multilingualism? Are traditional societies more, less, or equally often bilingual compared to modern state societies?
The distinction between bilingualism (or multilingualism) and monolingualism proves even more difficult to define and more arbitrary than is the distinction between a language and a dialect. Should you count yourself as
