Archive for February, 2011

Pour la Science article on Indo-European expansion


Phylogenetic models of language diversification seem to be popular these days in French popular science magazines. Of the leading publications, La Recherche will feature an interview with yours truly in March, and Pour la Science has an 8-page cover story on the subject in the current issue.

Popularizer Ruth Berger looks at the expansion of the Indo-Europeans from genetic and linguistic points of view, trying to reconcile them and to decide between the Kurgan (horsemen) and Anatolian (farmers) possible origins of Indo-European expansion. For the linguistics half, she looks at phylogenetic models to infer genealogies and dates, but skips the methodology and reproduces directly trees by Gray & Atkinson (2003) and Atkinson et al. (2005).

It is a shame that the method is presented as a black box. Given the length of the article, it would have been possible to give a general idea of how dates are inferred: the ages of parts of the tree are known, and this information is used to estimate rates of change and other ages. Instead, the author suggests that the rates are already known [whence?] and are fed to the black box, which magically outputs a tree and dates.  There is barely anything about the uncertainty of the estimates, and nothing about validation. I also have trouble understanding the points made at the end about Linear A and the attempt to merge the Anatolian and Kurgan hypotheses.

This issue is number 400 of Pour la Science. According to the editor-in-chief, they decided to celebrate with an issue on “theories and models”. Indo-European expansion is one of their examples, along with pieces on Grand Unification and on gene transfers. Uncertainty and validation are major parts of any decent modelling endeavour, and it is a shame that they did not seize the opportunity to educate their readership about these issues.

I suppose it is hardly surprising that I am disappointed with a popular science paper on a topic related to my PhD…