Tuesday, May 29, 2007
Note: The authors have a website which summarizes their research (via Language Log).
Speaking in tones? Blame it on your genes:
I first started hearing stuff this sort of research (i.e., the correlations between particular alleles and language forms) in 2006, so I'm not too surprised. We'll see how this pans out, look for it in PNAS.
But, which alleles on which genes? From Scientific American:
The new research, published this week in Proceedings of the National Academy of Sciences USA ties this difference to two genes, ASPM and Microcephalin. The exact functions of both genes are still open to debate, but they are known to affect brain size during embryonic development. "They presumably have something to do with brain structure, because there are deleterious mutations of the genes that lead to microcephaly" (a condition in which a person's brain is much smaller than the average size for his or her age), says senior study author, Robert Ladd, a professor of linguistics at the University of Edinburgh in Scotland.
First, note that the authors here imply that derived (more recent) forms of the genes in question under strong selection are connected to the spread of non-tonal languages around 6,000 years ago. There's a lot of question begging here, are tonal languages ancestral? Is this association causal? But look, there's one thing that jumps out at me from a cursory examination of the various times suggested here: it sees possible that the rise to prominence of non-tonal languages (assuming their derived character) dovetails with the posited expansions of Indo-European and Afro-Asiatic languages around the core of the World-Island (Eurasia + Africa).
Here is the wiki info on the geography of tonality:
In Europe, only Norwegian, Swedish, Scottish Gaelic, the Limburgish language (according to some a dialect of Dutch), Lithuanian, Serbian, Croatian, and some dialects of Slovenian possess tonality, and only Lithuanian regularly marks it in text other than in dictionaries. The tones of Lithuanian are believed to be especially authentic, as they agree for the most part with the tones of Vedic Sanskrit, its ancient cousin. Another Indo-European tonal language, spoken in the Indian subcontinent, is Punjabi.
Finally, from the authors' website:
The next step is to do experiments in which we look for evidence of the nature of the predisposition or bias. The work of Patrick Wong and his colleagues provides one possible lead here: they have shown that some monolingual adults find it much harder than others to learn an artificial language vocabulary that makes use of tone or pitch distinctions, and that the differences between these groups show up in subtle differences of brain structure as well. If we could show that these differences also reflect differences in genetic make-up, it would go some way to showing that the correlation we have found is based on a real causal link.
Related: This is Bruce Lahn's brain on ASPM and MCPH1. ASPM, Microcephalin, and intelligence. Developmental cell biology of ASPM. Brain size & genes.