Language evolves in sudden leaps, according to a statistical study of three major language groups. The finding challenges the slow-and-steady model held by many linguists and matches evidence that genetic evolution follows a similar path.

Mark Pagel from the University of Reading in the UK and colleagues applied statistical tools commonly used in biology to the analysis of three of the world’s major language groups: Indo-European, Austronesian, and Bantu.

By comparing commonly used words within each language group, they were able to identify the extent to which languages within a group diverged from the others. This enabled them to build a family tree, charting the divergence of one “mother tongue” into hundreds of daughter languages.

If languages change at a constant rate, the length of any branch back to the root of the language “tree” should be of the same length. But the researchers found that languages that are very different from the common root had longer paths. This suggests that, each time they split, an abrupt spurt of evolution occurs.


They found that up to a third of all vocabulary changes result from “punctuational bursts of change” when one language splits from another.

In 2005, Pagel performed a similar analysis of genetic variation in species of trees. He found that 22% of evolutionary change came during similar periods of rapid development in some species. “In one case its words, in the other case its genes,” Pagel says.

Pagel says languages may diverge suddenly when a subgroup separates from a larger population, to create a unique social identity. Similarly, genetic change may occur suddenly as genes try to adapt quickly to a new environment.

Pagel’s colleague Quentin Atkinson adds that, when a small group is isolated from a larger population, any idiosyncrasies in the way they speak may become amplified. “The same thing happens in biology where smaller founder populations are able to change more quickly,” he says.

Salikoko Mufwene a linguist at the University of Chicago, however, says it may be misleading to characterise language evolution as “abrupt”. “You don’t go to bed speaking one way and wake up speaking another way,” he says. “Languages may change over centuries, but that is not abrupt, that is gradual.”

Journal reference: Science (vol.319, p.588)

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