Human genetics and languages: Evolving in parallel?

A collaborative study headed by Stanford University found a surprising connection between worldwide populations and the evolution of their spoken languages.

The large-scale study called A comparison of worldwide phonemic and genetic variation in human populations, found that languages in more remote populations actually experience more phonemic change over time than languages that are surrounded by many others.

Phonemes are the sounds that form spoken language. They are the smallest unit of sound that distinguishes one word from another. Different languages can share phonemes, without sharing vocabulary.

Researchers looked at phonemic inventories of over 2,000 languages. The study was published in Proceedings of the National Academy of Sciences in January 2015.

What’s New

Phoneme inventories were studied alongside the genetic markers of more than 200 populations worldwide. Researchers in this study were inspired to see if language has evolved on par with genetics, says lead researcher Nicole Creanza.

“Over time and with colonization there is lots of opportunity for genes and languages not to evolve in parallel. So we wanted to see on a global scale, is the pattern we see primarily that of genes and languages following each other? Or are we going to see a lot of divergence based on this complex tradition?”

Historically, the study of genetic variation has led to important insight about the movement of human populations, says Creanza, a postdoctoral research fellow in the department of biology at Stanford University. The closer two populations are to each other, the more similar their genes are.

When a population is isolated from its neighbours their genes share less similarities with the original population. Within an isolated population there is little diversity due to a limited gene pool.

The smaller gene pool of the isolated population leads to little change amongst their genetics. However, isolated populations showed more susceptibility to change within their language, says Creanza.

It seems counter-intuitive, but a possible explanation for this susceptibility to change could be due to social forces, says Carleton University linguistics professor Beth MacLeod.

“Picture a small town,” MacLeod says. “If someone brings in a new word, everyone could start using it really fast.”

A major difference in the evolution of genetics versus language is the range of influence society can have on speech.

Different languages can share common sounds like "sh" and "th" without sharing vocabulary.
This audio compilation features dozens of phonemes from various languages,
 all saying the same phrase, "Hello, how are you?" in their various dialects.

 

“You inherit your genes from your parents,” Creanza says. “You can learn from a teacher, you can learn from you peers, and not just your parents.”

Although they share more phonemes with one another, populations with many neighbours appear more resilient to change in speech patterns.

“Maybe, you’d have less pressure to speak the same way as everybody else,” says MacLeod. “When you have a looser network you can start doing something new with speech and not everyone in your network is going to know about it right away.”

The study also found that neighbouring populations shared many phonemes, even between different languages. This could explain their apparent resilience to change, says MacLeod.

“The more populations have in common, phonetically, the less there is to change,” she says. “Where as if a population is more on their own they don’t have that same reinforcing effect of other languages using the same sound.”

The study, however, did not account for human interference in population such as colonization. So, for a country such as Canada, the focus of the study was on indigenous languages found in the various regions and not English or French.

“We tried to use a sample that was mostly dominated by indigenous cultures,” Creanza says. “We left it all up to the languages to tell their story.”

What’s Next

The massive sample of languages used in the study is valuable in discovering broad patterns, says Creanza. In order to better understand the direction of the genetics and language evolution, future research could isolate a specific population changing over time.

“We tried to do this on a global scale,” she says. “We have so few genetic samples compared to the languages we know about, so I think there is future collaborative efforts trying to use the linguistic analysis to inform future genetic studies.”