Genetics – Replicated Typo

Evolang Coverage: Simon Fisher: Molecular Windows into Speech and Language

In his clear and engaging plenary talk, Simon Fisher, who is director of the Department “Language & Genetics” at the Max-Planck-Institute for Psycholinguistics, the Netherlands, gave a summary of the current state of research on what molecular biology and genetics can contribute to the question of language evolution. Fisher was involved in the discovery of the (in)famous FOXP2 gene, which was found to be linked to hereditary language impairment in an English family. He has also done a lot of subsequent work on this gene, so naturally it was the also main focus of his talk.

But before he dealt with this area, he dispelled what he called the ‘abstract gene myth’. According to Fisher, it cannot be stressed enough that there is no direct relation between genes and behavior and that we have to “mind the gap”, as he put it. There is a long chain of interactions and relations that stand between genes one the one side, and speech and language on the other. DNA is related to the building of proteins, which is related to the development of cells. These in turn are related to neural circuits, which then relate to the human brain as whole, which then are related to speech and language.

So when we try to look at these complex net of relations, what we can say is that there is a subset of children which grow up in normal environments but still do not develop normal language skills. From a genetic perspective it is of interest that of these children, there are cases where these impairments cannot be explained by other transparent impairments like cerebral palsy, hearing loss, etc. Moreover, there are cases in which language disorders are heritable. This suggests that there are genetic factors that play a role in some of these impairments.

The most famous example of such a case of heritable language impairment is the English KE family, where affected members of the family are missing one copy of the FOXP2 gene. These family members exhibit impaired speech development. Specifically, they have difficulty in learning and producing sequences of complex oro-facial movements that underlie speech. However, they do show deficits in a wide range of language-related skills, including spoken and written language. It thus has to be emphasized that the missing FOXP2 gene seems to affect all aspects of linguistic development. It is also important that is not accompanied by general motor dyspraxia.

In general, non-verbal deficits are not central to the disorder. Affected individuals start out with a normal non-nonverbal IQ, but then don’t keep up with their peers, something that is very likely to be related to the fact that possessing non-impaired language opens the door for the enhancement of intelligence in various ways, something which people with only one FOXP2 gene cannot take advantage of to the same degree. In general, deficits in verbal cognition are much more severe and wide-ranging than other possible impairments. It is also important to note that after the FOXP2 gene was discovered in the KE family, researchers found a dozen of cases of a damaged FOXP2 gene that led to language-related problems.

FOXP2 is a so-called transcription factor, which means that it can activate and repress other genes. As Fisher points out, in a way FOXP2 functions as a kind of ‘genetic dimmer switch’ that tunes down the expression of other genes. In this context, it should become clear that FOXP2 is not “the gene for language.” Versions of FOXP2 are found in highly similar form in vertebrae species that lack speech and language. It therefore played very ancient roles in the brain of our common ancestor. Neither is FOXP2 exclusively expressed in the brain. It is also involved in the development of the lung, the intestines and the heart. However, work by Simon Fisher and his colleagues shows that FOXP2 is important for neural connectivity. Interestingly, mice with one damaged FOXP2 copy are absolutely normal in their normal baselines motor behavior. However, they have significant deficits in what Fisher called ‘voluntary motor learning.”

From an evolutionary perspective, it is relevant that there have been very little changes in the gene over the course of vertebrae evolution. However, there seem to have been more changes to the gene since our split from the chimpanzee lineage than there have been since the split from the mouse lineage. This means that when it comes to FOXP2, the protein of a chimpanzee is actually closer to a mouse than to a human.

Overall, what current knowledge about the molecular bases of language tells us is that these uniquely human capacities build on evolutionary ancient system. However, much more work is needed to understand the influence of FOXP2 on the molecular and cellular level and how these are related to the development of neural circuits, the brain, and finally our capacity for fully-formed complex human language.

Everett, Pirahã and Recursion: The Latest

Discussing the concept of recursion is like a rite of passage for anyone interested in language evolution: you go through it once, take a position and hope it doesn’t come back to haunt you. As Hannah pointed out last year, there are two definitions of recursion:

(1) embeddedness of phrases within other phrases, which entails keeping track of long-distance dependencies among phrases;

(2) the speciﬁcation of the computed output string itself, including meta-recursion, where recursion is both the recipe for an utterance and the overarching process that creates and executes the recipe.

The case of grammatical recursion (see definition 1) is perhaps most famously associated with Noam Chomsky. Not only does he claim all human languages are recursive, but also that this ability is biologically hardwired as part of our genetic makeup. Countering Chomsky’s first claim is the debate surrounding a small Amazonian tribe called the Pirahã: even though they show signs of recursion, such as the ability to recursively embed structures within stories, the Pirahã grammar is claimed not to recursively embed phrases within other phrases. If true, then are numerous implications for a wide variety of fields in linguistics, but this is still an unsubstantiated claim: for the most part, we are relying on one specific researcher (Daniel Everett) who, despite having dedicated a large portion of his life to studying the tribe, could very well have been misled. That said, I retain a large amount of respect for Everett, having watched him speak at Edinburgh a few years ago and read his book on the topic: Don’t Sleep, There are Snakes: Life and Language in the Amazonian Jungle.

So, why am I rambling on about recursion? Well, besides its obvious relevance, — and perhaps under-representation on this blog (deserved or not, I’ll let you decide) — Everrett has recently published a series of slides about a corpus study of Pirahã grammar (see below).

[gview file=”http://tedlab.mit.edu/tedlab_website/researchpapers/piantadosi_et_al_piraha_lsa_2012.pdf”]

His tentative conclusion: there is no strong evidence for recursion among relative clauses, complement clauses, possessive structures and conjunctions/disjunctions. However, there is possible evidence of recursive structure in topics/repeated arguments. He also posits cultural pressures for longer or shorter sentences, such as writing systems (as I mentioned way back in 2009).

I’m sure this debate will be brought to the fore at this year’s EvoLang, with ~~Chomsky~~ ~~Berwick~~ Piattelli-Palmarini and many of the Biolinguistic crowd in attendance, and it’s a shame I’ll almost certainly miss it (unless someone wants to pay for my ticket… Just hit the donate button in the left-hand corner 😉 ).

Continue reading “Everett, Pirahã and Recursion: The Latest”

Should Mother Tongue be Father Tongue?

A new paper, published in Science last week, has reviewed some of the correlations which suggest that language change may be subject to sex-specific transmission. This has been discovered through looking at Y-chromosome DNA types. Modern male DNA (Y-Chromosome) is found to be the DNA from the population who originally spoke the language which has survived, whereas modern female DNA is often not the DNA of the population which spoke the language which has survived.

This evidence has come from, among others, a study by Chaubey (2011) with evidence for the Indian subcontinent. Austroasiatic languages are spoken by tribes with a high proportion of immigrant Y-chromosome DNA from East Asia, but with a high percentage of local female (mitochondrial) DNA. This pattern was also true of the Tibeto-Burman language family in northeastern India.

Other studies found matching correlations in Africa and found that Niger-Congo languages correlate with Y-Chromosome types, but the female DNA, which correlated more with geography (Wood et al. (2005) and de Filippo et al. (2011)).

Sex-biased language change can also be seen in the expansion of the Malayo-Polynesians in New Guinea. New Guinea has populations of Malayo-Polynesian speakers and also populations of Melanesian speakers. Malayo-Polynesian female DNA is about the same in both Malayo-Polynesian speaking areas and Melanesian speaking areas. However, the Malayo-Polynesian Y-Chromosome is found way more in the Malayo-Polynesian speaking areas than the Melanesian speaking areas.

This pattern is also seen in Iceland where the female DNA is mainly British, but the Y-chromosome is mainly Scandinavian. This follows the pattern because the Icelandic language is also Scandinavian.

Forster and Renfrew (authors of the Science paper) show that these findings complement studies such as Stoneking and Delfin who found that in East Asia, it is women who move after marriage rather than men. This means that if a man and woman migrate to a populated area their female offspring will move to other villages when married but their male offspring will remain static meaning that their language will stay in the same place as their Y-Chromosomes.

Is this the only mechanism at work when correlations of sex-specific language change can be seen? Others have hypothesized things such as farming and trade might be a factor. Groups of emigrating agriculturalists may also contribute where men outnumber women and take wives from the local community they were moving to. Men are also biologically capable of passing on and spreading about much more of their DNA than women can. It may also be the case that it is the father’s language rather than the mother’s which will be dominant within a family but I think more research would have to be done on this.

Interestingly the opposite correlation to the ones seen above is seen in Greenland where both the language and female DNA is Eskimo but the Y-Chromosome DNA is European.

Phonemic Diversity Supports a Serial Founder Effect Model of Language Expansion from Africa

Just read about an article on phoneme diversity via GNXP and Babel’s Dawn. Hopefully I’ll share some of my thoughts on the paper this weekend as it clearly ties in with work I’m currently doing (see here and here). Below is the abstract:

Human genetic and phenotypic diversity declines with distance from Africa, as predicted by a serial founder effect in which successive population bottlenecks during range expansion progressively reduce diversity, underpinning support for an African origin of modern humans. Recent work suggests that a similar founder effect may operate on human culture and language. here I show that the number of phonemes used in a global sample of 504 languages is also clinal and fits a serial founder-effect model of expansion from an inferred origin in Africa. This result, which is no explained by more recent demographic history, local language diversity, or statistical non-independence within language families, points to parallel mechanisms shaping genetic and linguistic diversity and supports an African origin of modern human languages.

Reference: Atkinson, Q.D (2011). Phonemic Diversity Supports a Serial Founder Effect Model of Language Expansion from Africa. Science 332, 346. DOI: 10.1126/science.1199295.

Update: I’ve given a lengthier response here.

Fungus, -i. 2nd Decl. N. Masculine – or is it?: On Gender

In an attempt to write out my thoughts for others instead of continually building them up in saved stickies, folders full of .pdfs, and hastily scribbled lecture notes, as if waiting for the spontaneous incarnation of what looks increasingly like a dissertation, I’m going to give a glimpse today of what I’ve been looking into recently. (Full disclosure: I am not a biologist, and was told specifically by my High School teacher that it would be best if I didn’t do another science class. Also, I liked Latin too much, which explains the title.)

It all started, really, with trying to get my flatmate Jamie into research blogging. His intended career path is mycology, where there are apparently fewer posts available for graduate study than in Old English syntax. As he was setting up the since-neglected Fungi Imperfecti, he pointed this article out to me: A Fungus Walks Into A Singles Bar. The post explains briefly how fungi have a very complicated sexual reproduction system.

Fungi are eukaryotes, the same as all other complex organisms with complicated cell structures. However, they are in their own kingdom, for a variety of reasons. Fungi are not the same as mushrooms, which are only the fruiting bodies of certain fungi. Their reproductive mechanisms is rather unexpectedly complex, in that the normal conventions of sex do not apply. Not all fungi reproduce sexually, and many are isogamous, meaning that their gametes look the same and differ only in certain alleles in certain areas called mating-type regions. Some fungi only have two mating types, which would give the illusion of being like animal genders. However, others, like Schizophyllum commune, have over ten thousand (although these interact in an odd way, such that they’re only productive if the mating regions are highly compatible (Uyenoyama 2005)).

Some fungi are homothallic, meaning that self-mating and reproduction is possible. This means that a spore has within it two dissimilar nuclei, ready to mate – the button mushroom apparently does this (yes, the kind you buy in a supermarket.) Heterothallic fungi, on the other hand, merely needs to find another fungi that isn’t the same mating type – which is pretty easy, if there are hundreds of options. Other types of fungi can’t reproduce together, but can vegetatively blend together to share resources, interestingly enough. Think of mind-melding, like Spock. Alternatively, think of mycelia fusing together to share resources.

In short, the system is ridiculously confusing, and not at all like the simple bipolar genders of, say, humans (if we take the canonical view of human gender, meaning only two.) I’m still trying to find adequate research on the origins of this sort of system. Understandably, it’s difficult. Mycologists agree:

“The molecular genetical studies of the past ten years have revealed a genetic fluidity in fungi that could never have been imagined. Transposons and other mobile elements can switch the mating types of fungi and cause chromosonal rearrangements.Deletions of mitochondrial genes can accumulate as either symptomless plasmids or as disruptive elements leading to cellular senescence…[in summary,] many aspects of the genetic fluidity of fungi remain to be resolved, and probably many more remain to be discovered.” (Deacon, 1997: pg. 157)

At this point you’re probably asking why I’ve posted this here. Well, perhaps understandably, I started drawing comparisons between mycologic mating types and linguistic agreement immediately. First, mating-type isn’t limited to bipolarity – neither is grammatical gender. Nearly 10% of the 257 languages noted for number of genders on WALS have more than five genders. Ngan’gityemerri seems to be winning, with 15 different genders (Reid, 1997). Gender distinctions generally have to do with a semantic core – one which need not be based on sex, either, but can cover categories like animacy. Gender can normally be diagnosed by agreement marking, which, taking out genetic analysis of the parent, could be analogic to fungi offspring. Gender can be a fluid system, susceptible to decay, mostly through attrition, but also to reformation and realignment – the same is true of mating types. (For more, see Corbett, 1991)

As with all biologic to linguistic analogues, the connections are a bit tenuous. I’ve been researching fungal replication partly for the sake of dispelling the old “that’s too complex to have evolved” argument, which is probably the most fun point to argue against creationists with. However, I’ve mostly been doing this because fungi and linguistic gender distinctions are just so damn interesting.

If anyone likes, I’ll keep you updated on mycologic evolution and the linguistic analogues I can tentatively draw. For now, though, I’ve really got to get back to studying for my examination in two days. Which means I’ve got to stop thinking about a future post involving detailing why “Prokaryotic evolution and the tree of life are two different things” (Baptiste et al., 2009)…

References:

Corbett, G. Gender. Cambridge University Press, Cambridge: 1991.
Deacon, JW. Modern Mycology. Blackwell Science, Oxford: 1997.
Reid, Nicholas. and Harvey, Mark David, Nominal classification in aboriginal Australia / edited by Mark Harvey, Nicholas Reid John Benjamins Pub., Philadelphia, PA : 1997.

Uyenoyama, M. (2004). Evolution under tight linkage to mating type New Phytologist, 165 (1), 63-70 DOI: 10.1111/j.1469-8137.2004.01246.x
Bapteste E, O’Malley MA, Beiko RG, Ereshefsky M, Gogarten JP, Franklin-Hall L, Lapointe FJ, Dupré J, Dagan T, Boucher Y, & Martin W (2009). Prokaryotic evolution and the tree of life are two different things. Biology direct, 4 PMID: 19788731

Williams Syndrome, Modularity and Language Evolution

Williams Syndrome (WS) is a rare genetic condition which manifests itself as a severe deficit in development and IQ, however it leaves language ability largely unaffected and is, as a result, often cited as evidence for a specific language module (Bellugi et al. 1988), as language can be unaffected despite other mental deficits. This argument has a strong bearing on the evolution of language as it contributes to the debate of whether language evolved for language’s sake or whether it is as the result (an exaptation or spandrel) of general cognitive capability in other areas.

Work by Brock (2007) has shown that the language abilities of people with WS could be predicted by non-linguistic abilities (You could probably argue this of the language abilities of anyone, but that’s another blog post). It has also been shown that language acquisition in WS children is behind that of normal children. Many studies have shown deficits in WS children’s language (reflexive pronouns, grammatical morphems, verb raising, negative wh-sentences) which are generally put down to normal-but-delayed language acquisition as people with the condition will usually pick these grammatical rules up by adolescence.

Perovic and Wexler (2010) suggest that if some grammatical knowledge is shown not to be present in WS children by adolescence, (as is apparently the case with verb raising) then this is evidence to suggest not just ‘normal-but-delayed’ language, but in fact, ‘atypical’ language.

Perovic and Wexler (2010) did a study on 26 children with Williams Syndrome between the ages of 6 – 16. They were tested using picture matching comprehension tasks on passives featuring ‘actional’ verbs and ‘psychological verbs’. The results confirmed what has been seen in previous studies, that WS children can process actional passives with ease, but also showed a previously unreported deficiency in their ability to process psychological verbs.

They also found this deficiency in 5 adult sufferers of WS.

So it seems that the linguistic ability of people with WS is not so exceptional after all.

In the discussion of this paper it is explored as to whether these differences could just be down to the general cognitive impairments which people with developmental problems face. The fact that this question even needs to be discussed is evidence to contradict a ‘language module’ theory. That is that if the deficit in WS children’s passive is a specifically linguistic one then WS can no longer be used as evidence for affected intellectuality but unaffected language, and on the other hand, if it is as a result of general cognitive deficiency, then this is evidence to suggest that it is general cognitive ability that results in much, if not all, linguistic ability in the first place.

References

Bellugi, U. Marks, S. Bihrle, A. and Sbo, H. (1988) Dissociation between language and cognitive functions in Williams Syndrome. In D. Bishop and K. Mogford (Eds.) Language developement in excpetional circumstances (pp. 177 – 189). Hillsdale, NJ: Erlbraum

Brock, J. (2007) Language abilities in Williams syndrome: A critical review. Development and Psychopathology, 19, 97-127.

Perovic A, & Wexler K (2010). Development of verbal passive in Williams syndrome. Journal of speech, language, and hearing research : JSLHR, 53 (5), 1294-306 PMID: 20631227

On Phylogenic Analogues

A recent post by Miko on Kirschner and Gerhart’s work on developmental constraints and the implications for evolutionary biology caught my eye due to the possible analogues which could be drawn with language in mind. It starts by saying that developmental constraints are the most intuitive out of all of the known constraints on phenotypic variation. Essentially, whatever evolves must evolve from the starting point, and it cannot ignore the features of the original. Thus, a winged horse would not occur, as six limbs would violate the basic bauplan of tetrapods. In the same way, a daughter language cannot evolve without taking into account the language it derives from and language universals. But instead of viewing this as a constraint which limits the massive variation we see biologically or linguistically between different phenotypes, developmental constraints can be seen as a catalyst for regular variation.

A pretty and random tree showing variation among IE languages.

Looking back over my courses, I’m surprised by how little I’ve noticed (different from how much was actually said) about reasons for linguistic variation. The modes of change are often noted: <th> is fronted in Fife, for instance, leading to the ‘Firsty Ferret’ instead of the ‘Thirsty Ferret’ as a brew, for instance. However, why the <th> is fronted at all isn’t explained beyond cursory hypothesis. But that’s a bit besides the point: what is the point is that phenotypic variation is not necessarily random, as there are constraints – due to the “buffering and canalizing of development” – which limit variation to a defined range of possibilities. There clearly aren’t any homologues between biological embryonic processes and linguistic constraints, but there are developmental analogues: the input bottleneck (paucity of data) given to children, learnability constraints, the necessity for communication, certain biological constraints to do with production and perception, etc. These all act on language to make variation occur only within certain channels, many of which would be predictable.

Another interesting point raised by the article is the robustness of living systems to mutation. The buffering effect of embryonic development results in the accumulation of ‘silent’ variation. This has been termed evolutionary capacitance. Silent variation can lay quiet, accumulating, not changing the phenotype noticeably until environmental or genetic conditions unmask them. I’ve seen little research (not that I don’t expect there to be plenty) on the theoretical implications of the influence of evolutionary capacitance on language change – in other words, how likely a language is to make small variations which don’t affect language understanding before a new language emerges (not that the term language isn’t arbitrary based on the speaking community, anyway). Are some languages more robust than others? Is robustness a quality which makes a language more likely to be used in multilingual settings – for instance, in New Guinea, if seven languages are mutually indistinguishable, is it likely the that local lingua franca is forced by its environment to be more robust in order to maximise comprehension?

The article goes on about the cost of robustness: stasis. This can be seen clearly in Late Latin, which was more robust than the daughter languages as it was needed to communicate in different environments where the language had branched off into the Romance languages, and an older form was necessary in order for communication to ensue. Thus, Latin retained usage well after the rest of it had evolved into other languages. Another example would be Homeric Greek, which retained many features lost in Attic, Doric, Koine, and other dialects, as it was used in only a certain environment and was therefore resistant to change. This has all been studied before better than I can sum it up here. But the point I am making is that analogues can be clearly drawn here, and some interesting theories regarding language become apparent only when seen in this light.

A good example, also covered, would be exploratory processes, as Kirschner and Gerhart call them. These are processes which allow for variation to occur in environments where other variables are forced to change. The example given is the growth of bone length, which requires corresponding muscular, circulatory, and other dependant systems to also change. The exploratory processes allow for future change to occur in the other systems. That is, they expedite plasticity. So, for instance, an ad hoc linguistic example would be the loss of a fixed word order, which would require that morphology step in to fill the gap. In such a case, particles or affixes or the like would have to have already paved the way for case markers to evolve, and would have had to have been present to some extent in the original word order system. (This may not be the best example, but I hope my point comes across.)

Naturally, much of this will have seemed intuitive. But, as Miko stated, these are useful concepts for thinking about evolution; and, in my own case especially, the basics ought to be brought back into scrutiny fairly frequently. Which is justification enough for this post. As always, comments appreciated and accepted. And a possible future post: clade selection as a nonsensical way to approach phylogenic variation.

References:

Caldwell, M. (2002). From fins to limbs to fins: Limb evolution in fossil marine reptiles American Journal of Medical Genetics, 112 (3), 236-249 DOI: 10.1002/ajmg.10773

Gerhart, J., & Kirschner, M. (2007). Colloquium Papers: The theory of facilitated variation Proceedings of the National Academy of Sciences, 104 (suppl_1), 8582-8589 DOI: 10.1073/pnas.0701035104

New Language and Genetics department

Next week, on the 1st October, there will be a new language and genetics department opening at the Max Planck Institute, the first research department in the world entirely devoted to understanding the relationship between language and genes!!!

This excites me so I wanted to share the news.

This statement is from Simon Fisher, who will head the new department about what they will be trying to achieve:

‘We aim to uncover the DNA variations which ultimately affect different facets of our communicative abilities, not only in children with language-related disorders but also in the general population, and even through to people with exceptional linguistic skills’, says L&G director Simon Fisher. ‘Our work attempts to bridge the gaps between genes, brains, speech and language, by integrating molecular findings with data from other levels of analysis, particularly cell biology and neuro-imaging. In addition, we hope to trace the evolutionary history and worldwide diversity of the key genes, which may shed new light on language origins.’

More signs of the growing and diversifying field of language evolution!

Here’s a link to the news on the MPI website: http://www.mpi.nl/news/new-mpi-department-language-genetics

Genetic Anchoring, Tone and Stable Characteristics of Language

In 2007, Dan Dediu and Bob Ladd published a paper claiming there was a non-spurious link between the non-derived alleles of ASPM and Microcephalin and tonal languages. The key idea emerging from this research is one where certain alleles may bias language acquisition or processing, subsequently shaping the development of a language within a population of learners. Therefore, investigating potential correlations between genetic markers and typological features may open up new avenues of thinking in linguistics, particularly in our understanding of the complex levels at which genetic and cognitive biases operate. Specifically, Dediu & Ladd refer to three necessary components underlying the proposed genetic influence on linguistic tone:

[…] from interindividual genetic differences to differences in brain structure and function, from these differences in brain structure and function to interindividual differences in language-related capacities, and, finally, to typological differences between languages.”

That the genetic makeup of a population can indirectly influence the trajectory of language change differs from previous hypotheses into genetics and linguistics. First, it is distinct from attempts to correlate genetic features of populations with language families (e.g. Cavalli-Sforza et al., 1994). And second, it differs from Pinker and Bloom’s (1990) assertions of genetic underpinnings leading to a language-specific cognitive module. Furthermore, the authors do not argue that languages act as a selective pressure on ASPM and Microcephalin, rather this bias is a selectively neutral byproduct. Since then, there have been numerous studies covering these alleles, with the initial claims (Evans et al., 2004) for positive selection being under dispute (Fuli Yu et al., 2007), as well as any claims for a direct relationship between dyslexia, specific language impairment, working memory, IQ, and head-size (Bates et al., 2008).

A new paper by Dediu (2010) delves further into this potential relationship between ASPM/MCPH1 and linguistic tone, by suggesting this typological feature is genetically anchored to the aforementioned alleles. Generally speaking, cultural and linguistic processes will proceed on shorter timescales when compared to genetic change; however, in tandem with other recent studies (see my post on Greenhill et al., 2010), some typological features might be more consistently stable than others. Reasons for this stability are broad and varied. For instance, word-use within a population is a good indicator of predicting rates of lexical evolution (Pagel et al., 2007). Genetic aspects, then, may also be a stabilising factor, with Dediu claiming linguistic tone is one such instance:

From a purely linguistic point of view, tone is just another aspect of language, and there is no a priori linguistic reason to expect that it would be very stable. However, if linguistic tone is indeed under genetic biasing, then it is expected that its dynamics would tend to correlate with that of the biasing genes. This, in turn, would result in tone being more resistant to ‘regular’ language change and more stable than other linguistic features.

Continue reading “Genetic Anchoring, Tone and Stable Characteristics of Language”

Where does the myth of a gene for things like intelligence come from?

As a linguist I struggle with genetics, I am, however, as an evolution geek, very interested in it. This creates all sorts of problems and high levels of anxiety when talking about FOXP2 and other genes, due to fear that I misunderstand the very highly complex interactions which exist between genes, environmental effects or cascading effects which cannot be summed up in a simple “x gene causes x trait in humans” paradigm.

I would like to point everyone towards a new blog Dorothy Bishop’s written over at guardian science blogs:

Where does the myth of a gene for things like intelligence come from?

Which is about busting the widespread belief (for idiots like me) that individual genes determine traits such as intelligence, optimism, obesity and dyslexia. I find it interesting that this is presented in the blogs section and not as a mainstream article.

She points out on Twitter this morning that the Jedward pic was not her idea. (I add this point because I found it weirdly comforting)

And it’s also lovely to see that at the bottom of the pile of comments is a well articulated reply by Dorothy to individual users.

I love blogging, because there exists the ability for individuals to reply to claims made about them, primary sources (papers &c.) are cited and checkable and there’s none of the unnecessary dumbing down found in mainstream media. Here’s an article by Ben Goldacre expanding on this subject (which incidentally includes work by Dorothy Bishop).

Here is a parable about how, as a blogger, my claims were checked, discussed and ultimately concluded to be bollocks. (I don’t have a contrastive parable about what would have happened if I’d instead made these claims in the mainstream media but many stories of this nature can be found here.)

If you read the blog post I wrote about links between Autism and SLI you would have seen me make this claim:

the CNTNAP2 gene has been found in independent samples to be associated with both ASD and SLI. This is interesting because it could show that gene mutations which cause improved social abilities could have also caused changes in our linguistic ability on a syntactic or phonological level.

This blog post cited the work of Dorothy Bishop quite heavily and she took the time out to come and tell me problems with it. Here’s what she said:

As you anticipated, I think there are some problems with the implications you draw from the work. There are two issues. The first is that the variants of CNTNAP2 associated with language level are not mutations. You would usually only use that term in the case where most people had the same DNA sequence in a gene, but rare individuals had a different DNA sequence. FOXP2 is a case in point: there is a family, the KE family, who have a mutation affecting around half the family members, where the DNA sequence is changed. For most people in the general population, and for most people with SLI, the FOXP2 sequence is the same.

The CNTNAP gene is very different. The DNA sequence has different versions in different people, and one version, which is pretty common in the general population, is associated with a small decrease in language abilities, but most people with this version would not be recognised as having any language impairment. Most researchers now think that SLI is probably the result of the combined effect of many genes, each of which may nudge language ability up or down a bit. In this regard, language ability is rather like height: there are rare mutations that may make a person drastically tall or short, but most variation in height arises from combined effect of many small influences of genes that show DNA variation in the normal population.

The second issue concerns the evidence for CNTNAP2 being involved in both SLI and autism. Many people in the field do think this means that the same gene that can cause SLI can also cause autism, and that the only difference is that people with autism have additional difficulties going beyond language – what I have termed the ‘autism as SLI plus’ model. I supported that model in the past, but there are some facts that are hard to square with it. First, although many people with autism have structural language problems (affecting grammar and phonology) similar to those in SLI, not all of them do. So people with high-functioning autism or Asperger syndrome may have well-developed skills in syntax and phonology, while still having difficulties with pragmatics. The second point, which is a big problem for a simple genetic account, is that whereas the relatives of people with SLI often have some difficulties with structural language, we don’t usually see that in relatives of people with autism, even if the person with autism has poor language skills. It was this latter point that I was particularly keen to try and explain in my paper. The bottom line is that to explain the pattern of data we need to think in terms of interactions between genes (technically known as epistasis). So there are genetic variants that increase risk of autism, and others that increase risk of SLI. Most of these will have an individually small effect. However, if you have a risk variant for a gene influencing SLI (such as CNTNAP2) in the context of having a genetic risk for autism, the effect on language will be much worse. According to this model CNTNAP2 doesn’t affect both social cognition and language; rather it affects language, but that effect will get multiplied if the person also has risk factors for autism.

Which is SOOOO interesting.

I’d really like to thank her for replying, it’s really lovely to know that high-flying academics are willing to help out when a sincere blogger tries to understand something and falls on their arse.