ASPM -lexical tone association in speakers of a tone language: Direct evidence for the genetic-biasing hypothesis of language evolution

Abstract

How language has evolved into more than 7000 varieties today remains a question that puzzles linguists, anthropologists, and evolutionary scientists. The genetic-biasing hypothesis of language evolution postulates that genes and language features coevolve, such that a population that is genetically predisposed to perceiving a particular linguistic feature would tend to adopt that feature in their language. Statistical studies that correlated a large number of genetic variants and linguistic features not only generated this hypothesis but also specifically pinpointed a linkage between ASPM and lexical tone. However, there is currently no direct evidence for this association and, therefore, the hypothesis. In an experimental study, we provide evidence to link ASPM with lexical tone perception in a sample of over 400 speakers of a tone language. In addition to providing the first direct evidence for the genetic-biasing hypothesis, our results have implications for further studies of linguistic anthropology and language disorders.

Genetic influences on tone? New experimental evidence and its consequences for linguistics.

“…When we published our exploratory cross-population study in 2007, we imagined, rather optimistically, that experimental evidence, one way or the other, might be swift to follow, but it has taken 13 years. While far from being the last word on the possible link between ASPM and tone, we believe that Wong et al (2020) is an important step forward, not least because it shows how different paradigms and scientific fields can fruitfully inform each other and produce research that is simply not possible within either one by itself. It also shows that 'risky' exploratory studies can lay the groundwork for careful experimental work that yields genuine discoveries.…”

“…The fact that the relationship is the opposite of the expected one might be due, as themselves argue, to differences in methodology, to gene-gene and gene-culture interactions, and to the fact that the Wong eventually obtained funding for a much larger study that aimed to address some of these puzzles. In May 2020, he and his colleagues published a new paper (Wong et al 2020) reporting a very large study in which they tested more genes and more phenotypes, and used a more refined test battery. As in the 2012 study, they kept the linguistic and 'ethnic' backgrounds constant, but this time they focused on young adult native speakers of a language with a complex tone system, Cantonese;…”

“…The scores on the 'lexical tone perception' task vary between as low as 51% (the chance level is 50%) and 100%. While many of the participants are well above 90% (the average is 87%), a substantial number of participants performed below 75% (see Wong et al 2020, for multiple testing to investigate the association between the four tasks and the genotyped loci. Even after controlling for the positive significant effects of the covariates non-verbal IQ and years of musical training, the only significant association they found with the genetic variables was between the performance on the 'lexical tone perception' task and ASPM-D.…”

The Sound Systems of Languages Adapt, But to What Extent?

“…(Collins 2016) To further complicate matters, associations between tonality and population-level genetic factors exist. (Dediu & Ladd 2007, Wong et al 2020) Such varied and complex associations point to the difficulty of disentangling causal mechanisms in such typological data, particularly since direct experimental evidence is difficult to derive for such hypotheses based on probabilistic mechanisms operating over millennia. Nevertheless, it is worth stressing that indirect experimental evidence is consistent with the hypothesis.…”

Sinking in: the peripheral Baldwinisation of human cognition

“…Specialised neurocomputational mechanisms controlling these movements [84] and for perceiving rapid streams of subtly distinct sounds [85] are likely to have coevolved with the emergence of speech through Baldwinian evolution [86]. Moreover, regarding speech perception, there is intriguing evidence linking population frequencies of specific genes with speakers of languages with lexical tone (i.e., word identities are partly defined by pitch contours) [87], as well as experimental evidence that one such gene, ASPM, correlates with perception of lexical tone at the level of individual speakers [88]. Although causal direction is, of course, difficult to infer from such correlational data, these data fit with a two-way, Baldwinian, interaction of genes and speech perception.…”