Languages are a lot like living organisms. Both evolve over time, allowing an ancestral tongue like Latin to sire diverse descendants — Spanish, French, Romanian — that are more closely related to each other than to, say, Korean. This much is old news; Charles Darwin himself noted the resemblance. “The formation of different languages and of distinct species,” he writes in The Descent of Man, “are curiously parallel.”
Now, new research shows that the analogy runs deeper. Islands, long recognized as hotbeds of biological diversity, are just as much engines of linguistic diversity. Drawing on a global database of languages from more than 13,000 inhabited islands (with a size cutoff at about 4,250 square miles), researchers at the Australian National University discovered that some of the same evolutionary patterns hold true in both life and language.
Incredibly, although these islands make up less than 1 percent of Earth’s inhabited land, the study found that 10 percent of languages are endemic to them — spoken nowhere else. Compare that to Russia, where the ratio is exactly reversed — 10 percent of the world’s landmass, with a little over 1 percent of its languages. As lead author Lindell Bromham put it, islands “capture a disproportionate amount of both biodiversity and language diversity.”
Biologists solved the first half of that mystery long ago, so Bromham and her colleagues (all of whom come from the life sciences) decided they’d take a stab at the second half. “We in evolutionary biology,” she says, “have spent decades building up a suite of analytical tools to answer those kinds of questions.”
How Island Diversity Impacts Language
In 1967, the biologists Robert MacArthur and E. O. Wilson published The Theory of Island Biogeography, a landmark ecological text. In it, they proposed that the number of plant and animal species on any given island depends largely on two factors: its size and its distance from the mainland. The larger the island, the more species it can sustain; the closer to well-populated continents, the more species will stumble upon it in the first place.
In line with the theory’s predictions, Bromham and her co-authors, Keaghan J. Yaxley and Marcel Cardillo, found that the number of languages on an island increases with area. Once a language has become isolated from its continental forebears, it’s free to spread out across as much virgin territory as it can cover, transforming all the while and shooting forth new branches in the linguistic family tree.
As for the second tenet of island biogeography, the researchers didn’t find a straightforward relationship between language diversity and remoteness. This is probably because, while plants and animals only come ashore on distant islands by chance, humans colonize them deliberately. “They have ocean-going boats; they have star maps,” Bromham says. “They have the desire to get to a new land.” Our ancestors peopled the most lonesome reaches of the globe, from Hawaii to Easter Island, in the span of just a few thousand years.
These far-flung regions do, however, follow another important law of species diversity — they’re loaded with endemic languages. Though islands become increasingly less populated with distance, in terms of both species and languages, they’re comparatively rich in the proportion that exists exclusively on a lone chunk of land.
Read More: A New Look At Our Linguistic Roots
Researching the Evolution of Language
Islands are often referred to as evolutionary “laboratories”—places where evolution’s handiwork is so pronounced it slaps you in the face. As such, they’ve played an outsized role in shaping much of biological and ecological science. But the lessons they teach aren’t applicable only to literal islands; they also explain the fate of species in any ecosystem that’s surrounded by ecosystems of a different kind — mountain ranges, desert oases, even cities. These places may not be cut off from the world by the open ocean, but their barriers are no less impassable.
When it comes to language, however, it’s not clear that island dynamics apply to other insular ecosystems. In a 2015 study, Bromham and her colleagues found that most ecological boundaries don’t have the same influence on language that they do on species.
Rivers spur diversity in both cases, but not for the same reason — they isolate animals and plants, ensuring that populations evolve separately, whereas, for humans, they act as a resource that allows many small groups (and thus languages) to coexist. Other variables, like the roughness of the landscape and mountainous terrain, don’t seem to have a significant effect one way or the other.
All of which drives home an important reminder — tantalizing parallels aside, we are dealing with two different beasts. “On the one hand, we see similar patterns,” Bromham says, “but on the other hand, we always remember that languages aren’t the same as species.”
Read More: When Did Humans Evolve Language?
Island and Mainland Languages Differ in Sounds
Every language is made up of a unique set of “phonemes,” the basic sounds we use to form words. They’re not the same as letters, though they can be represented by various combinations of the Latin alphabet (“b,” “sh,” “ai,” and so on). Languages differ wildly in their phoneme inventory. English has 44, while the Taa language of southern Africa boasts somewhere upward of 100.
Here is perhaps the most baffling fact in Bromham’s paper. Island languages tend to have far fewer phonemes than mainland ones. If you were feeling provocative, you could equate phonemes to genes (both being the basic units of their respective systems), and then this would seem like another similarity between biology and language —as species migrate, they tend to split off into smaller and smaller “founder populations,” losing genetic diversity from the larger ancestral group.
Perhaps a language could lose phonemic diversity in the same way as its speakers dwindle during the long voyage from island to island. The problem is that it’s not obvious why this would happen. A handful of migrants can’t take the whole gene pool with them, but they can hold on to the full set of sounds in their mother tongue.
Another possibility is that in small, isolated populations, there aren’t many neighboring languages to muddy the phonetic waters, so speakers don’t need a repertoire that is as large as they need to communicate effectively and unambiguously. But for now, there’s no clear answer. “Our work has been pointing out the patterns but not giving the explanations,” Bromham says. “So it would be lovely to be able to build up the data to actually burrow into some of these questions.”
Read More: How Language Shapes Our Understanding of Reality
Safeguarding Linguistic Diversity
Yet another difference between island languages and island species, fortunately, is that the former do not face the same existential threats as the latter. Animals and plants are going extinct at alarming rates around the world, but on islands, they’re especially vulnerable. A 2021 “scientists’ warning” concluded that some 50 percent of all endangered species live on islands, though it included larger landmasses than Bromham’s study.
Languages are also in dire straits. One oft-cited estimate classifies nearly half of the 7,000 total as endangered. But based on this new study, island languages, in particular seem to be no more imperiled than their mainland counterparts. For some reason, they’ve been spared the extra risk that island species must confront.
Nevertheless, Bromham says that protecting island languages will be crucial to preserving language diversity worldwide simply because they account for such a disproportionate amount of said diversity. That, in the end, is what led her to this field of research. “We want to highlight how amazing it is that we have all these different solutions to human communication,” she says. “Each one of them represents amazing human creativity and inventiveness. Any language loss is a loss for all of us.”
Read More: How to Resurrect Dying Languages
Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
PLOS Biology. Across the Curious Parallel of Language and Species Evolution
Nature Ecology & Evolution. Islands are engines of language diversity
Lead author from Australian National University. Lindell Bromham
Cambridge University Press. Island Colonization
Nature Communications. The ecological drivers of variation in global language diversity
Global Ecology and Conservation. Scientists’ warning – The outstanding biodiversity of islands is in peril
The Endangered Languages Project. Endangered languages: Why so important?
Cody Cottier is a contributing writer at Discover who loves exploring big questions about the universe and our home planet, the nature of consciousness, the ethical implications of science and more. He holds a bachelor's degree in journalism and media production from Washington State University.
