On the genetic foundation of language

[Jacques Cinq-Mars]

I am kind of surprised that no one has felt an urge to bring up  this recent news  which has been spreading through the media like wildfire, since yesterday. It deals with a recent Nature report (apparently, this week's issue) in which authors claim to have identified and presumably, dated the first occurence of a mutational event that would have led to the emergence of language as we know it.  As  usual, the media blurbs range from pathetic to being somewhat uninformative and, at times, contradictory. In other words, I don't know what to make of it without having read the actual Nature paper. If someone on this Forum has had this opportunity, enlightening comments would be appreciated.

An exemple of what I am talking about can be found at (watch for the wrap):

http://www.washingtonpost.com/wp-dyn/articles/A17863-2002Aug14. html

Jacques Cinq-Mars

[Isabelle]

I just had a very quick look at the nature website and this is what I came across:

http://www.nature.com/nsu/020812/020812-6.html

The piece is (ungracefully I think) entitled "Gene explains dumb apes".

I don't have time to read it right now unfortunately, but will do so later. I'll have a proper look at the Nature site later as well.

regards,
ISabelle

[Jane Moore]

I can't download the article since I'm at home, but look forward to doing so when I'm back in the office. I did find these abstracts that I thought might be useful background reading - I hope I'm not breaking any rules by posting them here. I believe the first one is the manuscript that kicked off the FOXP2/language debate, and the two following it question the importance of this gene in specific cases:

Lai, CSL, Fisher, SE, Hurst, JA, et al. (2001) A forkhead-domain gene is mutated in a severe speech and language disorder. Nature 413:519-523.

Individuals affected with developmental disorders of speech and language have substantial difficulty acquiring expressive and/or receptive language in the absence of any profound sensory or neurological impairment and despite adequate
intelligence and opportunity(1). Although studies of twins consistently indicate that a significant genetic component is involved(1-3), most families segregating speech and language deficits show complex patterns of inheritance, and a gene that predisposes individuals to such disorders has not been identified. We have studied a unique three-generation pedigree, KE, in which a severe speech and language disorder is transmitted as an autosomal-dominant monogenic trait(4). Our
previous work mapped the locus responsible, SPCH1, to a 5.6-cM interval of region 7q31 on chromosome 7 (ref. 5). We also identified an unrelated individual, CS, in whom speech and language impairment is associated with a chromosomal translocation involving the SPCH1 interval(6). Here we show that the gene FOXP2, which encodes a putative transcription factor containing a polyglutamine tract and a forkhead DNA-binding domain, is directly disrupted by the translocation
breakpoint in CS. In addition, we identify a point mutation in affected members of the KE family that alters an invariant amino-acid residue in the forkhead domain. Our findings suggest that FOXP2 is involved in the developmental process that culminates in speech and language.

Meaburn, E, Dale, PS, Craig, et al. (2002) Language-impaired children: No sign of the FOXP2 mutation. Neuroreport 13(8):3.

A mutation in the FOXP2 gene has been found to be responsible for the autosomal dominant inheritance of a severe form of speech and language! impairment in a family known as KE. We genotyped the FOXP2 mutation for 270 4-year-old children
selected for low general language scores from a representative community sample of more than 18,000 children. No language-impaired child had the FOXP2 mutation. Although rare severe disorders such as those of the KE family are often caused by a single gene, common disorders such as language impairment are
more likely to be the quantitative extreme of the same multiple genetic factors responsible for heritability throughout the distribution.

Newbury, DF, Bonora, E, Lamb, JA, et al. (2002) FOXP2 is not a major susceptibility gene for autism or specific language impairment. Am. J. Hum. Genet. 70(5):1318-1327.

The FOXP2 gene, located on human 7q31 (at the SPCH1 locus), encodes a transcription factor containing a polyglutamine tract and a forkhead domain. FOXP2 is mutated in a severe monogenic form of speech and language impairment, segregating within a single large pedigree, and is also disrupted by a translocation in an isolated case. Several studies of autistic disorder have
demonstrated linkage to a similar region of 7q (the AUTS1 locus), leading to the proposal that a single genetic factor on 7q31 contributes to both autism and language disorders. In the present study, we directly evaluate the impact of the FOXP2 gene with regard to both complex language impairments and autism, through use of association and mutation screening analyses. We conclude that coding-region variants in FOXP2 do not underlie the AUTS1 linkage and that the gene is unlikely to play a role in autism or more common forms of language
impairment.

[Greg]

Here is the first paragraph of the paper:
Language is a uniquely human trait likely to have been a prerequisite for the development of human culture. The ability to develop articulate speech relies on capabilities, such as fine control of the larynx and mouth1, that are absent in chimpanzees and other great apes. FOXP2 is the first gene relevant to the human ability to develop language2. A point mutation in FOXP2 co-segregates with a disorder in a family in which half of the members have severe articulation difficulties accompanied by linguistic and grammatical impairment3. This gene is disrupted by translocation in an unrelated individual who has a similar disorder. Thus, two functional copies of FOXP2 seem to be required for acquisition of normal spoken language. We sequenced the complementary DNAs that encode the FOXP2 protein in the chimpanzee, gorilla, orang-utan, rhesus macaque and mouse, and compared them with the human cDNA. We also investigated intraspecific variation of the human FOXP2 gene. Here we show that human FOXP2 contains changes in amino-acid coding and a pattern of nucleotide polymorphism, which strongly suggest that this gene has been the target of selection during recent human evolution.


Nature AOP, published online 14 August 2002; doi:10.1038/nature01025


Molecular evolution of FOXP2, a gene involved in speech and language

WOLFGANG ENARD*, MOLLY PRZEWORSKI*, SIMON E. FISHER†, CECILIA S. L. LAI†, VICTOR WIEBE*, TAKASHI KITANO*, ANTHONY P. MONACO† & SVANTE PÄÄBO*

[Greg]

Now, my take on this:


This research has been around for some time.

These are not genes that cause language, or that had to evolve in a certain way for language to function.  This (and other genes we assume) are involved in language.

The two are not the same.  A gene can be involved in language to such an extent that if the gene "breaks" the language "breaks" in the so-affected individuals, but not have been necessary or even related to the evolution of language.

It is important to understand the distinction.

This is of course still important and interesting.  

[John Hawks]

I think the tremendously interesting part of the paper is what they don't say about population replacement. They attempt to demonstrate, and are quite clear in their effort, that the mode of evolution of the gene was a selective sweep, and they place the timing of that sweep very recently (though the date is itself mostly a guess). But they rule out the hypothesis that an expansion of a population which already carried the allele was responsible for its proliferation. Thus, the allele was not suddenly selected for, causing the proliferation of a population that already carried it; instead, it was selected for immediately when it arose, and spread rapidly through the existing human population. Their model is silent about just where the people lived who experienced this selection, which means that the selection could have occurred in a worldwide, multiregional population.

This is no small irony, since a "language gene" has been a hypothesis mostly associated with the African replacement model. But it makes perfect sense--an advantageous gene spreading widely across the human population in a short time is just the sort of thing that the multiregional model is supposed to explain.

[Jacques Cinq-Mars]

This, in response to Jane Moore's post.

Many thanks for passing on the abstracts. They do show, at least for those of us who are not very familiar with this particular aspect of the literature, that it is not a "done deal" and that there is a healthy debate going on. Something that is also supported by Greg's last post.

Now, with regards to the "rules", you don't have to worry. Posting an abstract the way you did (i.e., with full credit given to the authors and the journal), in the context of an ongoing discussion, is perfectly appropriate.

Jacques Cinq-Mars

[Alec Christensen]

I just sat down and read Enard et al.'s paper, and I agree with John Hawks' thoughts on it. The idea that the modern human form of the gene spread by a selective sweep is intriguing, and does seem to fit a multiregional model better than a replacement one.

As I understand it, this allele allows humans to control the vocal articulations we need for spoken language. It seems to me that such a mutation could be very adaptive to individuals in a population that already had some form of language: those who can communicate a greater quantity and quality of information to each other will be better off than those who cannot. How useful could it be in a population that did not already have some form of spoken language?

So an enticing scenario to me is one of a Middle Palaeolithic Old World full of interacting, interbreeding populations of proto-linguistic humans, across which a gene like this might spread in a matter of tens of generations. Its spread could well be mirrored in the archaeological record by the increases in complexity of material culture that have been associated with "anatomically modern humans;" this culture could then have lead to physical gracilization, as Loring Brace has long argued.

Of course, as Hawks points out, the dating of this selective spread is wide open, so this scenario will remain just a tad speculative for the foreseeable future. And I am sure that others will argue equally strenuously that this is yet another datum that "proves" the Out of Africa model. But isn't that the fun of this whole enterprise?

Alec Christensen

[ambyers]

I have not read the paper, as yet and certainly intend to. But I agree with Alec that if a mutation that enhances a sphere of behaviour distributes rapidly, that sphere of behaviour must already exist. If the behaviors are expressive in nature, then this suggests that a fairly sophisticated system of communication actions was already in place and this would be the "envirornment" that would select for this mutation. I would simply add to Alec's information conveyancing characterization of communication by emphasizing that the type of communication that the full expressivity that this claimed mutation affords modern speakers also allows us to perform a whole range of speech acts that would otherwise be impossible -- from declaring war to setting the bank lending rate.

Martin Byers

[lagarvelho]

Dr. Hawks:

I think the tremendously interesting part of the paper is what they don't say about population replacement. They attempt to demonstrate, and are quite clear in their effort, that the mode of evolution of the gene was a selective sweep, and they place the timing of that sweep very recently (though the date is itself mostly a guess). But they rule out the hypothesis that an expansion of a population which already carried the allele was responsible for its proliferation.


Why do they rule this out?

Thus, the allele was not suddenly selected for, causing the proliferation of a population that already carried it; instead, it was selected for immediately when it arose, and spread rapidly through the existing human population. Their model is silent about just where the people lived who experienced this selection, which means that the selection could have occurred in a worldwide, multiregional population.

But all the media reports(which is all I've seen so far, at least until I can get my hands on the Nature article in some form), make the claim --- presumably taken from the research --- that this gene somehow arose at the same time as "modern" humans did.  These reports go on to conclude, in good "media" fashion, that this gae "modern" humans some kind of advantage.  So either the data has been interpreted in a certain way or the media is mangling the data(or more probably, both).

This is no small irony, since a "language gene" has been a hypothesis mostly associated with the African replacement model. But it makes perfect sense--an advantageous gene spreading widely across the human population in a short time is just the sort of thing that the multiregional model is supposed to explain.

I'm not arguing with you here, but , obviously this is a case where different interpretations of the data can produce quite different conclusions.

Respctfully,
Anne G

[John Hawks]

>> But they rule out the hypothesis that an expansion of a population which
>> already carried the allele was responsible for its proliferation.

> Why do they rule this out?

They have two lines of argument. One is that most other genes in the human nuclear genome show no evidence for a population expansion--if an expansion actually did occur, then all genes should look the same. The other is that when examining the frequencies of the silent polymorphisms that they found, the non-ancestral allele (i.e. the new mutant) on average is a higher frequency than we would expect at random. That is to say, genetic drift in the absence of selection is a random process that can be disrupted by rapid episodes of selection, causing new silent mutations to have higher frequencies just because of their fortuitous linkage to the selected allele.

> But all the media reports(which is all I've seen so far, at least until I can get
> my hands on the Nature article in some form), make the claim --- presumably
> taken from the research --- that this gene somehow arose at the same time
> as "modern" humans did.  These reports go on to conclude, in good "media"
> fashion, that this gae "modern" humans some kind of advantage.  So either
> the data has been interpreted in a certain way or the media is mangling the
> data(or more probably, both).

The interpretation in the Nature paper is that the rise of the now-ubiquitous human allele may have been correlated with the first appearance of archaeological evidence of modern human behavior (citing Klein's Human Career). My guess is that they were just fishing for an archaeological correlate, since the story from archaeology is much more complex (though Klein has been writing about a "language gene" for a long time). I think it is quite credible that some aspect (or aspects) of "modern" human behavior was enabled by this allele. But even so, the gene does not address whether that evolutionary change happened in a single small population or a more global population--indeed a trait under strong selection cannot provide any evidence one way or another (an argument hashed out by morphologists long ago). I think the media reports on this have actually been pretty good, except for a frequent assumption that a recent selective replacement of a single allele must be synonymous with a recent population replacement--but since many in our field have not yet straightened out Templeton's gene tree vs. population tree argument I think science writers are doing a fine job.

[lagarvelho]

Dr. Hawks:

They have two lines of argument. One is that most other genes in the human nuclear genome show no evidence for a population expansion--if an expansion actually did occur, then all genes should look the same. The other is that when examining the frequencies of the silent polymorphisms that they found, the non-ancestral allele (i.e. the new mutant) on average is a higher frequency than we would expect at random. That is to say, genetic drift in the absence of selection is a random process that can be disrupted by rapid episodes of selection, causing new silent mutations to have higher frequencies just because of their fortuitous linkage to the selected allele.

That doesn't make any sense to me. . . .but then, I'm a Starving Writer, not a molecular geneticist.

>The interpretation in the Nature paper is that the rise of the now-ubiquitous human allele may have been correlated with the first appearance of archaeological evidence of modern human behavior (citing Klein's Human Career). My guess is that they were just fishing for an archaeological correlate, since the story from archaeology is much more complex (though Klein has been writing about a "language gene" for a long time).

The archaeological story is indeed more complex than that, and I have a stack of academic papers in my personal files that suggest this.  To be absolutely straight, what Klein has been speculating about for a long time is not so much a "language gene" as a brain mutation that somehow enabled "modern" language.  For those who believe such things, this new study may strengthen their beliefs, but I have a definite impression that many in the field don't take the idea of *brain mutations* all that seriously, however long Klein has been claiming them.


I think it is quite credible that some aspect (or aspects) of "modern" human behavior was enabled by this allele. But even so, the gene does not address whether that evolutionary change happened in a single small population or a more global population--indeed a trait under strong selection cannot provide any evidence one way or another (an argument hashed out by morphologists long ago). I think the media reports on this have actually been pretty good, except for a frequent assumption that a recent selective replacement of a single allele must be synonymous with a recent population replacement--but since many in our field have not yet straightened out Templeton's gene tree vs. population tree argument I think science writers are doing a fine job.

The media reports have all tended to assume that this gene somehow originated in the "modern" population, which somehow gave them the "edge" which is a rather irritating assumption. . . .but that's another story.
Anne G

[caldararo]

Dear Jacques:

    I am not surprised that there was little response on the list.  The surprising think is that the authors made such an absurd claim, yet in the course of the logic of their new evolutionary philosophy where any base pair substitution is the beginning of a new species event this makes sense.  If ,however, we consider this claim in the context of the tradition of evolutionary thinking the absurdity becomes clear.  If they claim that the gene,  FOXP2, which is involved in the face and jaw movements and "involved" is the key here, differs from chimpanzees in a significant evolutionary sense (ie random mutations in individuals are not what they have "found" or copy errors, etc. but the result of devlopmental and evolutionary trends, then the idea that heterozygotes who are human have the ability to speak but chimps not, then the real absurdity follows from their logic (in their words) that those with two copies have the human condition but those with only one copy have  considerable difficulty speaking.  Such nonsense should not arouse our attention except it comes from such a respected source.  Does this mean then that those with only one copy are only half human?  It also brings up the entire concept of humanness which seems to make some AMH just H.s. and others super H.s.s.  The direction this reasoning is going is rather frightening to me.  But then  the atmosphere we are living in seems to be producing such ideas.

Niccolo Caldararo
Dept. of Anthro
SFSU

[lagarvelho]

Niccolo:

<<   I am not surprised that there was little response on the list.  The surprising think is that the authors made such an absurd claim, yet in the course of the logic of their new evolutionary philosophy where any base pair substitution is the beginning of a new species event this makes sense. >>

The real problem is, this kind of thinking has been around for *at least* the last 15 years or so, and has become increasingly accepted by a wide variety of people.  In this context,  it makes a lot of sense that  such a claim would be appear to make sense.  

<< If ,however, we consider this claim in the context of the tradition of evolutionary thinking the absurdity becomes clear.  If they claim that the gene,  FOXP2, which is involved in the face and jaw movements and "involved" is the key here, differs from chimpanzees in a significant evolutionary sense (ie random mutations in individuals are not what they have "found" or copy errors, etc. but the result of devlopmental and evolutionary trends, then the idea that heterozygotes who are human have the ability to speak but chimps not, then the real absurdity follows from their logic (in their words) that those with two copies have the human condition but those with only one copy have  considerable difficulty speaking.  Such nonsense should not arouse our attention except it comes from such a respected source.  Does this mean then that those with only one copy are only half human?  It also brings up the entire concept of humanness which seems to make some AMH just H.s. and others super H.s.s.  The direction this reasoning is going is rather frightening to me.  But then  the atmosphere we are living in seems to be producing such ideas.>>>

I can see where you're going with the logic of the "counterclaim", but from what I've gathered so far, that's not exactly what they're saying.  Of course, they claim chimps don't have this gene(or only one copy of it), but they *also* claim that the second copy(if I understand their reasoning correctly), evolved recently, just like "real" humanness did --- about 200-100 kyr ago.  This is the real absurdity of their claim, IMHO.  Especially in view of the fact that apparently genes involved in speech are spread over several chromosomes and probably have been added incrementally.
Anne G

[caldararo]

Good review by Jane and Greg's comments are well taken.  The authors of the article are stretching the boundaries of evolutionary thought as I  mentioned before.  Language does not rely on the present physiology of speech as many of those involved in animal research have shown, as American Sign Language proves, as the "click languages" demonstrate.  The mistake the autors of this article make, and which is made over and over again in the realm of what is called molecular anthropology is the belief that single gene changes are additive, that somehow a few gene changes and you can go from a chimp to a human.  It is the old "ontogeny recapitultes plylogeny" routine that Gould so effectively demolished  building on von Baer and others.  Not that Haeckel was entirely wrong but you cannot understand human evolution by using chimps as building blocks and saying that by changing a gene here or there you will then have a human.  Nevertheless, I will leave those interested in that debate to read Gould.  Luckily, my article discussing the problem this kind of thinking is creating regarding species ideas was just published today by Human Nature Review (thank you Ian).  For those who want to read the details of my criticism of how a mechanistic view of molecular biology is threatening the fundamental nature of biological classification, please go to: http://human-nature.com/nibbs/02/caldararo.html.  I certainly look forward to any comments or criticisms of my views.

Niccolo Caldararo
Dept. of Anthro
SFSU