If you ever wondered as a child who invented the English language, the answer might have surprised you: no one did. We got this incredibly sophisticated system of communication from no particular person. Languages just sort of sprung up and evolved, just like biological organisms.

But is their evolution really like-life? How does the process happen? These questions have been addressed and analyzed in theoretical models, but there are competing explanations that are difficult to discriminate between. A group of researchers has constructed and performed a study to test how languages change in different environments, and the new results could provide clues about the underlying mechanisms by which languages evolve.

The aim of the study was to test how the language-using population size affects the rate of change. Languages lose old words and gain new words all the time—but does that happen faster or slower when there are large populations of speakers?

After all, larger populations have more innovation going on—there are more people, so a lot of words could be gained that way. But smaller populations might acquire words more quickly because the smaller number of people makes it easier for a new word to diffuse throughout the entire population. And small populations might lose words faster because they’re more prone to random drift. Then again, larger populations might lose words faster because they’re prone to simplifying their language, casting off useless or redundant words.

All of these ideas have been suggested in earlier work. But in order to find out how significant these effects were, the trick was to make a controlled study comparing word gain and word loss to population size, which can be difficult to test. For one thing, it’s not clear how much can be statistically learned by comparing two related languages to each other—just in the same way that it might not be statistically significant to poll three people from the same household on whether they watch TV. This is known as Galton’s problem.

To work around this and other problems, the researchers chose a closely related language family, the Polynesian languages. Besides their close relationship, the language group was an ideal choice because its history (and the history of its speakers) has been well-defined through archaeology.

The study focused on basic vocabulary words that were cognates across the Polynesian languages. Cognates are words that share a common etymology, like the English "night" and German "nacht," which both mean the same thing. Cognates don’t always share the same meanings, because word meanings drift over time, sometimes producing similar-sounding words with differing meanings, like the English "raisin" and French "raisin" (meaning ‘grape’).

Choosing to restrict the study to basic vocabulary kept it simple because meaning doesn’t shift as easily and because basic vocabulary is relatively resistant to absorbing words from other cultures.

What the researchers found is that larger populations gain new words faster and smaller populations lose words more quickly.

These results effectively ruled out a few proposed effects as significant in the course of language evolution. One such effect is the founder effect, wherein, when a new colony with a small group is started, words from the parent group’s language are quickly abandoned by the colonists. The founder effect, however, seems to have played essentially no role in the development of the Polynesian languages.

But the results could lend support to models which compare language elements to genetics—specifically, the process by which words are gained and lost could then be analogous to positive selection, a mode of natural selection in evolution. This is not conclusive, however, as the authors acknowledge that there are other known explanations that could account for their observations.

The results don’t explain why smaller populations lose words more quickly while large populations are faster gainers. But the researchers point out that their results are consistent with random drift leading to word loss in the smaller populations and with more word innovations in the larger populations leading to faster word gain.

Further work is required to see how widely these results apply. If they do turn out to be truly general, the work will have implications for understanding the diversification of language families. It could even be useful for archaeology itself, as a greater understanding of language evolution can help piece together the history of human cultures.

PNAS, 2015. DOI: 10.1073/pnas.1419704112 (About DOIs)