If you were to travel through West Africa, going from Senegal in the northwest to Cameroon in the southeast--an area smaller than the United States--you would encounter more than 700 distinct languages, some as different from one another as Chinese and English. Cameroon, with a population of 12 million, is home to 275 languages; tiny Togo has about 50. This plenitude of tongues has puzzled linguists. The inhabitants, after all, are not mutually isolated by massive mountains as are the peoples of Papua New Guinea, the only place in the world with a linguistic diversity exceeding West Africa’s.
Now Daniel Nettle, a linguistic anthropologist at Oxford, has a new theory that may explain how such a Babel evolved. Nettle has been studying the distribution of West African languages for four years, comparing ecological maps with maps showing the ranges of various languages, something no one had done before. He noted, as have others, that languages become more numerous toward the equator. But Nettle noticed something else: a direct correlation between the length of the rainy season and the number of languages in a region. In his study, Nettle divided the West African countries into squares--each several thousand square miles in area--and counted the number of speakers of each language per square. He then compared this with the rainfall on each square.
In the south, where the rainy season lasts 11 months, he found the greatest concentration of languages--in some places as many as 80 per square. Farther north, in dry savanna lands with less than four months of rain, the number of languages fell, dropping to an average of three per square near the Sahara.
Thus Niger, a vast, arid country, has only 20 languages; while farther south, equally large but wetter Nigeria has 430. Languages with the tiniest range--such as Hórom, spoken by 500 people in northern Nigeria--may be restricted to a single village. Villagers typically are multilingual or speak a lingua franca that enables them to trade or marry into a neighboring clan. Skeptics might object that the south’s linguistic diversity merely reflects the region’s greater population density. But Nettle points out that in one of the most populous areas--northern Nigeria- -a single language, Hausa, dominates.
Nettle now believes he knows how these languages developed. If you have abundant rainfall year-round, then you can pretty much produce all the food you need, he says. Contact with the outside world is not essential to survival. But in areas with more seasonal crops, where failures can bring famine, relations with other groups become crucial. If you have six dry months, you can’t produce food for that period, says Nettle. So you need to form a social network, which can bring in the food. And the larger the network, the greater the likelihood of a common language.
West African societies largely conform to Nettle’s theory. In the south, yams, sweet potatoes, and cassavas are the staple crops. Though they need almost constant rain, they are reliable crops that can be harvested throughout the year. Thus their growers can live in small groups and speak a language that no outsider understands. In northern Nigeria or Ghana, where the rain falls for only six months, the staples are cereals like millet and sorghum. Although these can be stored during the dry season, shortfalls do occur, so trade--and a common language--becomes important. The trend continues even farther north, near the Sahara, where Fulani cattle herders range over vast distances.
This linguistic richness may not last. I suspect that in a couple of hundred years in Nigeria, you are not going to find 400-odd languages, Nettle says. You might find 40. If you can understand Hausa, spoken by 20 million people, you can watch tv, you can get hold of currency, which can give you medicine and fertilizer, he says. The big languages have become much more attractive because what they offer now is access to the whole industrial economy.