[ExI] speaking of genes

[Damien Broderick]

Genes might help you learn Chinese

Tuesday, 29 May 2007
Hamish Clarke
Cosmos Online
http://www.cosmosmagazine.com/node/1349

SYDNEY: Healthy babies can learn any language, 
but new research suggests that genes might play a 
part in learning tonal languages like Chinese.

Dan Dediu and Robert Ladd from the University of 
Edinburgh in Scotland found a genetic difference 
between people who speak tonal languages – such 
as Chinese and most languages of sub-Saharan 
Africa – and those who speak non-tonal languages like English.

"Our work raises the possibility of taking a new 
look at the relation between genes and language," 
said Ladd, reporting in the U.S. journal 
Proceedings of the National Academy of Sciences.

The language each person speaks has traditionally 
been considered an entirely cultural trait, 
determined no more by genes than religious 
beliefs or musical preferences. As evidence, 
scientists point to the fact that regardless of 
ancestry, any normal baby learns the languages it 
hears during its early years.

But now Dediu and Ladd believe they may have 
found the first evidence that genes are involved 
in acquisition of specific language types.

In tonal languages, subtle changes in pitch can 
radically alter the meaning of a word. So a 
non-native Chinese speaker enquiring after the 
health of someone's mother might easily enquire 
about the wellbeing of their horse instead.

In non-tonal languages this is not the case, 
although tone is still used to express emotion, 
convey sarcasm or indicate a question.

Dediu and Ladd examined published data on 49 
distinct populations from around the world, 
looking for the distribution of two genes for 
brain development: ASPM and Microcephalin. They 
then searched for correlations between different 
forms of each gene and 26 different linguistic features.

The authors found that there is generally no link 
between genes and linguistic features, but a 
strong negative correlation emerged between 
speakers of tonal languages and recently evolved 
forms of ASPM and Microcephalin. That is, people 
with the older forms of these genes were more 
likely to speak tonal languages, even when biases 
for geography and history were removed.

Ladd believes that discovering a causal link 
between population genetics and language 
structure would be big news, but says he and 
Dediu haven't found that link yet. "We've just 
demonstrated some very unlikely correlations that 
suggest there might be such a link."

As science uncovers more about specific genetic 
influences, "society is ... going to have to 
start dealing with a lot of policy questions that 
have only been theoretical up till now," said 
Ladd. He cites research on the genetic influences 
over dyslexia as one example. Should parents, 
educators or speech pathologists be given access 
to a child's genetic information in this case?

Bruce Lahn, a geneticist from the University of 
Chicago, published the dataset on ASPM and 
Microcephalin on which Dediu and Ladd's work is partly based.

"The work is highly significant if confirmed," 
Lahn said. "It is, to my knowledge, the first 
attempt to relate linguistic features, 
traditionally considered to be purely cultural, 
with a possible genetic contribution."

The authors hope that future experiments will 
reveal the path by which ASPM and Microcephalin 
exert their influence on individual brains, and 
ultimately, on the preferences of entire 
populations for different types of language.