Linguistics: Genetic component to tonal and atonal languages?

The Economist magazine (UK, center-left economics and news magazine) has an article on a statistical analysis by Dan Deidiu and Robert Ladd of the University of Edinburgh that shows a correlation between genetics and speaking a tonal or atonal language.

Aside: A tonal language is one where the pitch (tone) used when pronouncing a word changes its meaning.

Finding a correlation in itself is not surprising as most Asian languages are tonal. Where this study might lead, when combined with work by others, is to uncovering which came first - genetic differences that led to the development of tonal/atonal languages or language differences that became tied to genetics.