Linguistic tone is related to the population frequency of the adaptive haplogroups of two brain size genes, ASPM and Microcephalin
- School of Philosophy, Psychology and Language Sciences, University of Edinburgh, 14 Buccleuch Place, Edinburgh EH8 9LN, United Kingdom
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Edited by Henry C. Harpending, University of Utah, Salt Lake City, UT, and approved April 12, 2007 (received for review December 7, 2006)
Abstract
The correlations between interpopulation genetic and linguistic diversities are mostly noncausal (spurious), being due to historical processes and geographical factors that shape them in similar ways. Studies of such correlations usually consider allele frequencies and linguistic groupings (dialects, languages, linguistic families or phyla), sometimes controlling for geographic, topographic, or ecological factors. Here, we consider the relation between allele frequencies and linguistic typological features. Specifically, we focus on the derived haplogroups of the brain growth and development-related genes ASPM and Microcephalin, which show signs of natural selection and a marked geographic structure, and on linguistic tone, the use of voice pitch to convey lexical or grammatical distinctions. We hypothesize that there is a relationship between the population frequency of these two alleles and the presence of linguistic tone and test this hypothesis relative to a large database (983 alleles and 26 linguistic features in 49 populations), showing that it is not due to the usual explanatory factors represented by geography and history. The relationship between genetic and linguistic diversity in this case may be causal: certain alleles can bias language acquisition or processing and thereby influence the trajectory of language change through iterated cultural transmission.
Footnotes
- †To whom correspondence should be addressed. E-mail: bob{at}ling.ed.ac.uk
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Author contributions: D.D. and D.R.L. designed research; D.D. and D.R.L. performed research; D.D. and D.R.L. analyzed data; D.D. was primarily responsible for genetic data and statistical analysis; D.R.L. was primarily responsible for language data; and D.D. and D.R.L. wrote the paper.
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The authors declare no conflict of interest.
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This article is a PNAS Direct Submission.
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See Commentary on page 10755.
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↵ ‡ This is the number of logistic regressions for which the algorithm converged.
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↵ § Giving the three-letter language codes (4). These linguistic attributions are not unique in some cases.
- Abbreviations:
- ASPM-D,
- the derived (adaptive) haplogroup of the gene ASPM;
- MCPH-D,
- the derived (adaptive) haplogroup of the gene Microcephalin;
- DV,
- dependent variable;
- IV,
- independent variable.
- © 2007 by The National Academy of Sciences of the USA
