By a strictly linguistic definition of 70% intelligibility—the definition that one has to use in New Guinea, where no tribe has its own army or navy—quite a few Italian “dialects” would rate as languages. That redefinition of some Italian dialects as languages would close the gap in linguistic diversity between Italy and New Guinea slightly, but not by much. If the average number of speakers of an Italian “dialect” had equaled the 4,000 speakers of an average New Guinea language, Italy would have 10,000 languages. Aficionados of the separateness of Italian dialects might credit Italy with dozens of languages, but no one would claim there to be 10,000 different languages in Italy. It really is true that New Guinea is linguistically far more diverse than is Italy.
How languages evolve
How did the world end up with 7,000 languages, instead of our all sharing the same language? Already for tens of thousands of years before language spread by the Internet and Facebook, there has been ample opportunity for language differences to disappear, because most traditional peoples have had contact with neighboring peoples, with whom they intermarry and trade, and from whom they borrow words and ideas and behaviors. Something must have caused languages, even in the past and under traditional conditions, to diverge and to remain separate, in the face of all that contact.
Here’s how it happens. Any of us over the age of 40 has observed that languages change even over the course of just a few decades, with some words dropping out of use, new words being coined, and pronunciation shifting. For instance, whenever I revisit Germany, where I lived in 1961, young Germans notice that they have to explain to me some new German words (e.g., the new word Händi for cell phones, which didn’t exist in 1961), and that I still use some old-fashioned German words that have been going out of use since 1961 (e.g., jener/jene for “that/those”). But young Germans and I can still mostly understand each other well. Similarly, you American readers under the age of 40 may not recognize some formerly popular English words like “ballyhoo,” but in compensation you daily use the verb “to Google” and the participle “Googling,” which didn’t exist in my childhood.
After a few centuries of such independent changes in two geographically separate speech communities derived from the same original speech community, the communities develop dialects that may pose difficulties for each other to understand: e.g., the modest differences between American and British English, the bigger differences between the French of Quebec and of metropolitan France, and the still bigger differences between Afrikaans and Dutch. After 2,000 years of divergence, the speech communities have diverged so much as to be no longer mutually intelligible, although to linguists they are still obviously related—such as the French and Spanish and Romanian languages derived from Latin, or the English and German and other Germanic languages derived from proto-Germanic. Finally, after about 10,000 years, the differences are so great that most linguists would assign the languages to unrelated language families without any detectable relationships.
Thus, languages evolve differences because different groups of people independently develop different words and different pronunciations over the course of time. But the question remains why those diverged languages don’t merge again when formerly separated people spread out and re-contact each other at speech boundaries. For instance, at the modern boundary between Germany and Poland, there are Polish villages near German villages, but the villagers still speak a local variety of either German or of Polish, rather than a German-Polish mish-mash. Why is that so?
Probably the main disadvantage of speaking a mish-mash involves a basic function of human language: as soon as you start to speak to someone else, your language serves as an instantly recognizable badge of your group identity. It’s much easier for wartime spies to don the enemy’s uniform than to imitate convincingly the enemy’s language and pronunciation. People who speak your language are your people: they’ll recognize you as a compatriot, and they’ll support you or at least not be immediately suspicious of you, whereas someone speaking a different language is apt to be regarded as a potentially dangerous stranger. That instant distinction between friends and strangers still operates today: just see how you (my American readers) react the next time that you’re in Uzbekistan, and you finally to your relief hear someone behind you speaking English with an American accent. The distinction between friends and strangers was even more important in the past (Chapter 1), often a matter of life and death. It’s important to speak the language of at least some community, so that there will be some group that considers you as “our own.” If you instead speak a mish-mash near a speech boundary, both groups may understand much of what you say, but neither group will consider you “one of our own,” and you can’t count on either group to welcome and protect you. That may be why the world’s speech communities have tended to remain thousands of separate languages, instead of the whole world speaking one language or forming one dialect chain.
Geography of language diversity
Languages are distributed unevenly around the world: about 10% of the world’s area contains half of its languages. For instance, at the low-end extreme of language diversity, the world’s three largest countries—Russia, Canada, and China, each with an area of millions of square miles—have only about 100, 80, and 300 native languages respectively. But at the high-end extreme of language diversity, New Guinea and Vanuatu, with areas of only 300,000 and 4,700 square miles respectively, have about 1,000 and 110 native languages. That means that one language is spoken over an average area of about 66,000, 49,000, and 12,000 square miles in Russia, Canada, and China respectively, but only over 300 and 42 square miles respectively in New Guinea and Vanuatu. Why is there such enormous geographic variation in language diversity?
Linguists recognize ecological, socio-economic, and historical factors apparently contributing to the answer. Language diversity—e.g., the number of native languages per 1,000 square miles of area—correlates with numerous potentially explanatory factors, but these factors are in turn correlated with each other. Hence one has to resort to statistical methods, such as multiple regression analysis, to tease out which factors have primary effects actually causing language diversity to be high or low, and which other factors have just apparent effects mediated by their correlations with those primary factors. For example, there is a positive correlation between Rolls-Royce car ownership and lifespan: Rolls-Royce owners live on the average longer than do people who don’t own Rolls-Royces. That’s not because Rolls-Royce ownership directly improves survival, but because Rolls-Royce owners tend to have lots of money, which enables them to pay for the best health care, which is the actual cause of their long lifespans. When it comes, though, to correlates of linguistic diversity, there isn’t yet a corresponding agreement about the actual underlying causes.
The four closest ecological correlations of language diversity are with latitude, climate variability, biological productivity, and local ecological diversity. First, language diversity decreases from the equator towards the poles: all other things being equal, tropical areas hold more languages than do equivalent areas at higher latitudes. Second, at a given latitude language diversity decreases with climate variability, whether the variability consists of regular within-year seasonal variation or of unpredictable between-year variation. For instance, language diversity is higher in tropical rainforests that are wet all year round than in adjacent more seasonal tropical savannahs. (This factor of seasonality could account at least in part, through the correlation between latitude and seasonality, for the higher language diversities in the less seasonal tropics than in strongly seasonal high latitudes.) Third, language diversity tends to be higher in more productive environments (e.g., higher in rainforests than in deserts), though again at least some of that effect could be because of a tendency for deserts and many other unproductive environments to be strongly seasonal. Finally, language diversity is high in ecologically diverse areas and tends especially to be higher in rugged mountainous areas than in flat areas.
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These four ecological relationships are just correlations, not explanations. Suggested underlying explanations involve human population size, mobility, and economic strategies. First, a speech community’s viability increases with its number of people: a language spoken by only 50 people is more likely to disappear, due to its speakers all dying or abandoning their language, than is a language spoken by 5,000 people. Hence regions with a lower biological productivity (supporting fewer people) tend to support fewer languages, and to require more area for the speakers of each language. A viable population in Arctic or desert regions needs tens of thousands of square miles to support itself, while a few hundred square miles would be ample in productive landscapes. Second, the more constant is the environment between seasons and between years, the more self-sufficient and sedentary can a speech community be within a small area, without much need to move periodically or to trade for necessities with other peoples. Finally, an ecologically diverse area can support many different language communities, each with its 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 bilingual only if you can converse fluently in a second language besides your mother tongue? Should you count languages in which you can converse clumsily? What about languages that you can read but not speak—e.g., Latin and classical Greek for those of us who learned those languages at school? And what about languages that you can’t speak, but that you can understand when spoken by others? American-born children of immigrant parents often can understand but not speak their parents’ language, and New Guineans often distinguish between languages that they can both speak and understand, and languages that they say that they can only “hear” but not speak. Partly because of this lack of agreement on a definition of bilingualism, we lack comparative data on the frequency of bilingualism around the world.