In the past few years, a number of biologists have published studies suggesting various facts about the evolution of languages. This is not terribly surprising, I suppose, since historical linguistics and evolutionary biology share a long lineage. Darwin's (1859) Origin of Species was probably influenced by studies such as Franz Bopp's (1816) Über das Conjugationssystem der Sanskritsprache (On the Conjugation System of Sanskrit) and others in historical linguistics.1
Some of these studies have been noted with approval; others have been roundly criticized.
A brief report by Atkinson, Meade, Venditti, Greenhill & Pagel published in Science falls into the former category.2 The authors looked for evidence of punctuated evolution in three language families: Bantu, Austronesian and Indo-European. As in evolutionary biology, some historical linguists theorize that the development of languages remains relatively stable for a time, punctuated by rapid changes, such as the development of new dialects or languages.
Atkinson et al. compared the apparent rate of lexical change within language families by looking for cognate terms for basic vocabulary items. Using Swadesh lists for each language family, they calculated the number of cognates in various languages within the family.
Atkinson et al. assume that if there is no punctuated evolution, the percentage of cognates should show no relation to the number of branches in the linguistic family tree. On the other hand, if those branches (the development of new languages) cause a burst of new vocabulary, there should be greater lexical diversity and fewer cognates along portions of the family tree with more branching.
The authors find "significantly more lexical change along paths in which more new languages have emerged," which they take to be evidence of punctuated evolution. They conclude,
Our results, representing thousands of years of language evolution, identify a general tendency for newly formed sister languages to diverge in their fundamental vocabulary initially at a rapid pace, followed by longer periods of slower and gradual divergence. Punctuational bursts in phonology, morphology, and syntax, or at later times of language contact, may also occur.
There is (as is always the case in science) room to disagree with Atkinson et al. Some historical linguists, for example, tend to doubt any such broad-brush theories of language change. Atkinson et al. do, however, seem more careful and presumably therefore more reliable than some widely reported work.
Atkinson et al. mention two possible explanations for such rapid change: a founder effect, which might occur when a few speakers of a language move to a new area (see, e.g. Mufwene 1996 for a use of the founder effect in sociolinguistics); or the development of distinction for social reason. For more on this second point, see most of the field of sociolinguistics. The paper's own references to Labov 1994 and Chambers 1995 are not bad places to start.
Atkinson, Quentin D., Andrew Meade, Chris Venditti, Simon J. Greenhill & Mark Pagel. 2008. Languages evolve in punctuational bursts. Science 319(5863), 588.
Chambers, J.K. 1995. Sociolinguistic Theory: Language Variation and its Social Significance. Cambridge, MA: Blackwell.
Labov, William. 1994. Principles of Linguistic Change: Internal Factors. Oxford: Blackwell.
Mufwene, Salikoko. 1996. The founder principle in creole genesis. Diachronica 13(1), 83-134.
1. Scholars disagree about how directly Darwin may have been influenced by philology and historical linguistics, but the notion of "descent with modification" emerged in both biology and philology at around the same time. As a linguist, I'm inclined to note that Bopp's work appeared a generation before Darwin's. A biologist, on the other hand, might suggest that Bopp and his contemporaries were in turn influenced by Carl Linneaus.
2. Pagel, Atkinson & Meade are similarly responsible for the letter titled "Frequency of word-use predicts rates of lexical evolution throughout Indo-European history," which I noted last year.