Hong Kong scientists have discovered that the presence of polymorphism rs41310927 gene ASPM in the human genome to determine whether his native language to the tone. After analyzing the genome of 426 native speakers of Cantonese, scientists have found that the presence of this variant explains only the differences in how the participants perceive lexical tone, but no other sound information. In addition, most (84 percent) of the participants were carriers of T-allele rs41310927, and the allele correlated with how well native speakers perceive tones. The obtained data may be the first direct evidence for a genetic basis of language development, write the scientists in the Science Advances.
One of the hypotheses explaining language development and why the different languages, suggests that certain linguistic features developed and established in the language due to the fact that their speakers are genetically predisposed to this trait to understand and to reproduce in speech. Scientific evidence in favor of this hypothesis, however, still received little.
One of the only such evidence discovered in 2007, the correlation between genes, mutations of which are associated with the development of microcephaly, and whether or not the tongue to tone (use pitch as similarsocial units, common in Asia and Africa). So, scientists have found that the rarer in the genome population is found rs41310927 polymorphisms of the gene ASPM and rs930557 gene MCPH1, the more likely it is that the native language of this population — tone.
The correlation allowed us to make the assumption that genes, mutations of which are involved in the formation of microcephaly, can adjust the way a person perceives the spatial and temporal characteristics of sound to which the tone belongs. Another argument in favor of this hypothesis were the results of other studiesthat have indicated that mutations of the gene ASPM are associated with differences in the structure of the transverse temporal gyrus — part of the auditory cortex, which is involved in the perception of tones.
Patrick Vaughn (Patrick Wong) from the Chinese University of Hong Kong and his colleagues decided to examine in more detail the relationship between genes, variants of which are associated with the development of microcephaly, and perception of tones. Their study involved 426 native speakers of Cantonese dialects — varieties of Yue, common in southern China and Hong Kong. Participants had no neurological disorders and hearing impairments, and they all, in addition to the demographic data provided information about how did music, and passed the tests for General level of intelligence and working memory.
All volunteers passed the saliva for genome-wide analysis, as well as performed several tasks. In the first task participants were included a set pseudoself, the relevant phonological rules to Cantonese, and asked to determine equal or no tone was used in the first and last word. In the second task, the participants included two tunes, one with one note could differ in height, and were asked to identify whether the different melodies from each other. The third task was similar to the second except that the melody could vary between pitch and rhythm.
The researchers analyzed the relationship between several associated with microcephaly polymorphisms (including rs41310927 gene ASPM) and the results of all the trainees ‘ jobs: and so they were able to delimit the connection between polymorphisms and the perception of lexical tones and the perception of any other sound information. From all the analyzed associations were statistically significant, only the relationship between the polymorphisms of ASPM (rs41310927) and how well the participant recognizes lexical tones (p = 0.039). The frequency of T-alleles rs41310927 in the genomes of participants was 84 percent, and the C-alleles of 16 per cent; moreover, carriers of T-allele among the participants also better recognize the tone.
The scientists thus discovered a direct correlation between the gene ASPM and lexical tone perception in the population of native speakers of Cantonese. The studied polymorphism was not correlated with any other differences in auditory perception, and how well the participants perceived the tones, in turn, was not associated with any other examined genes, also associated with microcephaly.
The authors noted that not saying that ASPM is the only gene that is responsible for the perception of tones; their results, however, can be regarded as a direct (and, according to them, the first) argument in favor of the fact that linguistic evolution is largely determined by the genetic differences of the populations: populations in which the desired allele is more common, will be more likely to speak a tone language.
It is also worth noting that the work of scientists and their findings based on the hypothesis that ASPM is primarily expressed in the auditory cortex (specifically in the Department, which is responsible for perception of sound tones). In their work, scientists didn’t tested (on human beings it is impossible to check), but he based his hypothesis on the received earlier data. Of course, to clarify the relationship between ASPM and perception of tones will need further investigation.
Of course, in favor of the genetic component of language evolution tells not only the connection of the gene ASPM with the perception of tones. Two years ago, for example, scientists found that how much the language of consonants, responds to the polymorphism of a regulatory element that is responsible for the expression of DCDC2 gene that is associated with the processing of phonological information.