Once upon a time there was population genetics, and then we applied it to folklore (Image: Buyenlarge/Getty)

Once upon a time there were two girls. One was kind and helpful and was rewarded with a box of gold. The other was mean and lazy and was rewarded with a box of snakes. You may know another version of this fairy tale though, because it changed as it spread across Europe. A new study of how it changed shows that people who came from different language groups – or who lived a few hundred kilometres apart – were more likely to have children with each other than to exchange their version of the story. Analysing folklore in this way, using techniques from genetic analysis, may give us new insights into how cultures evolve.

There are numerous versions of the “kind and unkind girls” tale across Europe. Quentin Atkinson at the University of Auckland, New Zealand, and colleagues took a database of 700 versions collected a century or more ago in 31 languages, and quantified their differences. They then analysed these variations using standard techniques from population genetics, used to determine how common mutant versions of a gene are according to ethnic group or across a region.

“We are the first to include both those variables, so we can tease the effect of linguistic boundaries apart from geography,” says Atkinson. He found that both factors matter. “Two French versions of the tale collected 100 kilometres apart should differ as much as a French and a German version collected 10 kilometres apart,” he says. By the same token however, he found that a French version of the tale from near the German border might be more similar to a German version from just across the border than to another French variant found hundreds of kilometers away.


Stopped at the border

The analysis also shows that the tale crosses borders less readily than genes. There are very few consistent genetic differences between groups of Europeans that speak different languages; the team found that there were ten times as many divergences in the way two groups told the folk tale as there were genetic differences. In other words, it has been easier for Europeans to interbreed than share their stories.

“The results are quite reasonable,” says Peter Richerson of the University of California at Davis, whose team used the World Values Survey to show larger cultural than genetic differences between ethnic groups.

“We need to quantify more such cultural variables,” says Atkinson, to settle how cultures evolve.

Such analysis may also give us historical insights. Applying a method for tracing a gene’s family tree to the folk tale, Atkinson found that German-speaking Swiss tell the Italian version, not the German one. But the British tell the German tale – as do the Danes, Irish and Latvians. Maybe storytellers travelled medieval Baltic trade routes, speculates Atkinson. His team is analysis more folk tales to see if they cluster in the same way.

Journal reference: Proceedings of the Royal Society B, doi.org/kd8