Linguistic tone and genetics

The relationship between genes and language is probably the most difficult and delicate area of the language evolution debate. On the one hand, your individual language is clearly not chosen by your genes (a child can learn whichever language it is raised with) but the capacity for language has always been assumed to have a clear genetic basis, even if the Chomskian linguists have made no effort to explain how it evolved. The discovery of the FOXP2 gene gave hope that some part of the genetic basis of language had been found, but as yet there have been no major genetic breakthroughs to explain the Language Acquisition Device. What little examination there has recently been on the genetic basis for language, has begun to focus on the idea that there is a far for sophisticated relationship between the genetic and the linguistic layer. In this interesting model, subtle iterated changes can manifest in language over generations, motivated by slight genetic variations. A brilliant new paper by the Edinburgh LEC’s own (and rather lovely) Bob Ladd and Dan Dediu has really put the cat amongst the pigeons by finding a correlation between allele frequency in two genes and the proportion of tonal languages.

Its more an interesting correlational hypothesis at the moment than a proven link, but it does offer an interesting window onto the relationship between genes and language. Previous work into two genes, ASPM and Microcephalim showed that there were two common variants (alleles). The distribution of these genes throughout the world’s population is quite uneven and they are spreading quickly. Ladd and Dediu noticed that not only are these genes implicated in brain development, but they correlate nicely with the distribution of tonal languages throughout the world. They argue that this might be explained by the gradual imposition of slight genetic restrictions upon language across generations. Clearly each tonal language is different and this is not by any means the most significant way of categorizing a language, but if true it would indicate an incredibly subtle and iterated relationship between the genetic aspects of language, and the mechanisms of learning and cultural transmission.

Whatever your take on the causes of this correlation, the degree of similarity are striking. Perhaps another step forwards towards understanding the relationship between genes language and culture?


9 Responses to “Linguistic tone and genetics”

  1. 1 languageevolution September 21, 2007 at 6:32 am

    Another nail in the “FOXP2, it’s the language gene!” argument. The relationship is so much more subtle and interesting than some Chomskians want it to be.

  2. 2 jim davis April 21, 2008 at 4:38 pm

    Does anyone know if there has been any research done in the area of iodine supply and the development of language? I understand that those who are not exposed to iodine in youth do not learn to speak.

    Is it possible early humans that moved from the interior of Africa to the coastal areas encountered an environment which included foods which contained levels of iodine? Studies have shown that iodine, obtained in early childhood can increase human IQ by 3 to 5%.

    A reliable iodine supply, over a number of generations, could have been enough to enable a population to be more successful in a number of ways including language development followed by human population migration up the East cost of sub-Saharan Africa and out the rest of the Earth.

  3. 3 languageevolution April 23, 2008 at 6:59 am

    I have not heard anything about this but it sounds fascinating. I’m going to try and find out and hopefully post on it in future.

  4. 4 jim davis April 28, 2008 at 4:03 pm

    I’m not sure that there is anything on this anywhere. Would be nice if thee were. So far its pure conjecture on my part.

    A few years ago while working with my local Kiwanis Club I learned about the positive and negative effects of iodine on humans through their project to provide iodine salt plants around the world to help children.

    Later I was reading about genetic migration pattern research and it was mentioned that about 60,000 years ago humans began spreading along the coasts of the world from sub-Saharan Africa. It was theorized that early populations of modern humans were forced to move from the interior to the coasts, probably due of climate change. It was also theorized that there some kind of epiphany was experienced (Language development was mentioned as one of the possibilities) prior to or during the early stages of the spread of populations out of the African Continent.

    My conjecture draws on the fact that (1) iodine is important to individual human language development (2) iodine is most plentiful in the oceans and as a result in the flora and fauna that is supported by the oceans (3) the timing of events related to genetic migration evidence i.e. relative dates between 60,000 and 80,000 years ago (4) and the supposed development of language around the time of the increase of population leading to the spread of these people along the coasts of the Earth.

  5. 5 languageevolution April 29, 2008 at 9:28 pm

    Jim, I’m fascinated by this idea, but agree, there’s bugger all on it available on the internet. So a few questions we need to answer:
    How exactly does iodine deficieny affect language? Is it implicated as a developmental chemical or does it affect the day-to-day running of the brain?
    Do you know if it is affecting the brain, and thus language itself, or whether it impairs a related motor system?
    Is sufficient iodine available inland if you follow an average mixed diet?
    What is the effect of excessive iodine? Does it relationally improve development?

    Your idea reminds me a lot of the Aquatic Ape Hypothesis, a deeply unfashionable anthropological theory that is making a bit of a comeback at the moment. It argued that the common ancestor of the hominids went through an aquatic wading stage which gave birth to many of our modern features, walking upright, hairless bodies and crucially, the access to the oily fish allowed the brain to develop.
    Although, in relation to this post, I guess we are talking about a slow iterated process rather than a sudden evolutionary magic bullet (and evolution doesn’t do ‘magic bullets’). I does seem possible that access to iodine could have been a crucial factor in the development of language over an evolutionary timescale. I’ll mention this to Dan Deidu when I next see him.

  6. 6 languageevolution April 29, 2008 at 9:48 pm

    Hmm, fascinating. Iodine is a developmental chemical, implicated in an awful lot of different parts of the body. Language is just affected as a peripheral system, it seems. Access to Iodine is therefore not specific to language defiencies, but is bloody developmentally important.

    + here’s a couple of articles on iodine and evolution. Cunnane seems to be the only person who has published on thinks like this before.

  7. 7 jim davis May 1, 2008 at 12:43 am

    Afternoon, and thanks so much for the input… (Sorry, what is your given name) I have been intrigued by this subject for a long time now but have had no one to discuss it with.

    By now I think that you might agree that we are not looking at an evolutionary advancement (magic bullet) so much as an environmental one. Keep in mind that we are talking about an anatomically modern human population. I’ve never thought much of the Aquatic Ape theory… seemed a little far-fetched… but what do I know?

    Yes, iodine is available all over the world and, from what I have read, tends to decrease as you go up in altitude from sea level. It resides in the soil and enters the food chain in the normal ways. The supplies can be inconsistent from place to place: being almost nonexistent in some places while in near by areas it can be more than sufficient for positive human development.

    One study I read (conducted in an iodine deficient area in China in the 90’s) showed results that would indicate that a fetus requires iodine as early as possible for optimum development. Once it is acquired in the necessary amount (very small) it does not seem to have any additional developmental advantage. This study identified results up to as much as a 10% IQ advantage over the subjects that did not receive it during incubation at all. This study group also had physiological problems that limited their quality of life. Subjects who received iodine in the 2nd or 3rd trimesters also had an IQ defecate (3 to 7%) when compared to those who received it during the 1st trimester.

    I don’t know but it would seem that for optimum effect you need a consistent source at or above the minimum requirement, for a period of 3 or 4 generations to begin see the kind of advancements, and sudden population growth, that genetic migration trackers say they see. The sea seems to be the ideal, iodine rich, environment for this to take place.

    FYI the two links did not work

  1. 1 Rethinking FOXP2 « NCWC-BIO101-Intro to Life Science Trackback on September 21, 2007 at 2:00 am
  2. 2 Rethinking FOXP2 - Pusshe Trackback on October 26, 2007 at 7:13 pm

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September 2007

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