Review of FOXP2 and its role in brain development, speech, and the evolution of language

Edmund Blair Bolles over at Babel's Dawn discusses a very interesting review of "FOXP2 and the role of cortico-basal ganglia circuits in speech and language evolution" by Wolfgang Enard. Be sure to check it out!

Below you can find the abstract of the review:

"Purpose of the review

A reduced dosage of the transcription factor FOXP2 leads to speech and language impairments probably owing to deficits in cortical and subcortical neural circuits. Based on evolutionary sequence analysis it has been proposed that the two amino acid substitutions that occurred on the human lineage have been positively selected. Here I review recent studies investigating the functional consequences of these two substitutions and discuss how these first endeavors to study human brain evolution can be interpreted in the context of speech and language evolution.

Recent findings

Mice carrying the two substitutions in their endogenous Foxp2 gene show specific alterations in dopamine levels, striatal synaptic plasticity and neuronal morphology. Mice carrying only one functional Foxp2, show additional and partly opposite effects suggesting that FOXP2 has contributed to tuning cortico-basal ganglia circuits during human evolution. Evidence from human and songbird studies suggest that this could have been relevant during language acquisition or vocal learning, respectively.

Summary

FOXP2 could have contributed to the evolution of human speech and language by adapting cortico-basal ganglia circuits. More generally the recent studies allow careful optimism that aspects of human brain evolution can be investigated in model systems such as the mouse.

Highlights

► First functional studies investigate human FOXP2 evolution in a mouse. ► Human-specific properties of FOXP2 are specific to cortico-basal ganglia circuits. ► These properties might be relevant for language acquisition and/or vocal learning."

News on FOXP2

There are some interesting posts on new work done on FOXP2. The human version of the gene, which is implicated in vocal coordination and language in some way among a lot of other functions, was inserted into mice who also possess a version of foxp2 that influences, among other things, erly ultrasonic vocalizations. The brain led to changes in neural organization but otherwise bodily development was normal. One implication of this is that the changes in the human version of FOXP2 probably affect neural development, which is quite an ecxiting find.

There are posts on the paper by Enard et al. over at:

Anthropology.net

Gene Expression

The Loom

Update:

Ed Yong of Not Exactly Rocket Science also has a nice post up on the topic

I'm back! (of course with a piece on the evolution of language)

After a long and excruciating period of having no proper access to the internet I am finally back online.

It seems as if I missed quite a lot of interesting things while I was away, and I only just began to put all my favorite blogs into my new newsreader (I really really love the Opera newsreader function), but I'll try to start posting on a weekly basis again. I'm almost done reading Michael Tomasello's (2008) new book, “The Origins of Human Communication.”

But for starters, here are some interesting recent things that caught my eyes when I first browsed the blogosphere yesterday after my long hiatus (well, at least, it felt like a pretty long time to me):

Deric Bownds linked to an interesting essay in Nature by Eörs Szathmáry & Szabolcs Számadó on the evolution of language.

Szathmàry is an interesting figure. Although he is a biochemist, he often explores interdisciplinary culture-related issues from the perspective of theoretical evolutionary biology. In his 1997 book “The Major Transitions in Evolution”, which he coauthored with the famous biologist John Maynard Smith, he

“set out 8 “major transitions” in the evolution of life. These are events in the history of our planet that signal radical changes in the way evolution works. They start with a change in the way molecules replicate in the very earliest stages of the origins of life, through the emergence of DNA, and go on to include larger-scale later phenomena like the evolution of colonies where once there were only solitary individuals. What makes the work of these two eminent evolutionary biologists so interesting for us is their inclusion of the most recent evolutionary transition: the emergence of language” (Kirby 2007)

(taken from Kirby 2007)

So that's the context for his current essay. In it Szathmáry & Számadó delve a bit more into the details of language evolution and place of language in the “suite” of interconnected higher-order cognitive traits.

They argue that

“we shouldn't be trying to understand one characteristically human trait in isolation from the others. Moreover, instead of the brain being a collection of separate modules, each dedicated to a specific trait or capacity, humans are likely to have a complex cognitive architecture that is highly interconnected on multiple levels.” (Szathmáry & Számadó 2008).

They speculate that language might have helped early humans to hunt large game in the Late Pleistocene 120,000 years ago, and was only later co-opted for other functions.

As many researchers do, they also stress that language probably

“evolved in a highly social, potentially cooperative context, involving and requiring at least three attributes: shared attention, shared intentionality and theory of mind. In other words, individuals would have been able to pay attention to the same scene or object as others; be aware that they must act as a group in order to achieve a common goal; and attribute mental states to others as well as to themselves.” (Szathmáry & Számadó 2008)

This of course refers to the line of research done by Michael Tomasello an others, who have tried to pry out exactly these socio-cognitive traits that enable the unique form of human communication.

But Szathmáry & Számadó give this whole field of research an interesting spine when they consider the relationship between genetics and the “suite” of social, linguistic or tool-use-related cognitive traits.

If one gene plays a part in many traits, its evolution consequently affects not only the traits that it was originally selected for, but also many others. This that means if one gene changes because it increases, for example, tool-use proficiency, it might also affect, say, the development of language capacities, because it is involved in their expression as well.

Genes that evolved for different functions thus might form

“a network of interacting effects, in which evolution in one trait builds on an attribute already modified as a by-product of selection acting on another. The nature of the gene networks underpinning complex behaviour suggests that several genes will have been selected for because they enhanced proficiency in a range of tasks.”

Studying whether genes involved in one trait, like cooperation, also have an influence on other traits in the human cognitive suite opens up a new and exciting field of research.

They also propose a new metaphor for viewing the human mind:

“The distinct gene networks and brain regions underpinning each trait can be likened to the separate towers of a castle, which are connected by common rooms and corridors.” (Szathmáry & Számadó 2008)

Szathmáry & Számadó go on to cite some interesting parallels between several kinds of cognitive/linguistic proficiencies and deficiencies, lending support to the view that many cognitive traits are functionally interconnected.

One example I particularly liked was that

“as shown by people with syntax deficiencies being poor at drawing hierarchical structures, capacities can be synergistic, where proficiency in one domain means proficiency in another.”

I especially liked this example because it directly relates to Ray Jackendoff's (e.g. 2007) theory that one of the major building blocks of our linguistic capacities is the ability to process, create and store in mind pieces of combinatorial hierarchical structures of different formats. Here's his take on the issue:

“Evidence is mounting that much temporally sequenced hierarchical structure is constructed by the same part of the brain [...] whether the material being assembled is language, dance [...], hand movements [...], or music […].
Language use [...] requires temporal sequencing and the online construction of hierarchical structure, both of which appear also in motor control, the planning of action [...], and probably visual action perception – not to mention music.
Thus all higher mental capacities make use of the same sorts of basic machinery: memory, attention, and the construction of structure. What differentiates these capacities from each other, however, is the character of the structures they build and how these structures interact with the rest of the mind. (Jackendoff 2007: 388)”

The implications of Szathmáry & Számadó's article to research done by people like Ray Jackendoff and Michael Tomasello are at the moment quite fuzzy but I think that it would be very interesting trying to integrate these approaches and see where this would be heading. Also, there are a lot more interesting things I've found on the internet, especially a couple of quite nice articles in the current issue of Science magazine, but I'll write more about that in my next post.

References:

Jackendoff, Ray (2007): Linguistics in Cognitive Science: The State of the Art, The Linguistic Review 24, 347-401.

Kirby, S. (2007). The evolution of language. In Dunbar, R. and Barrett, L., editors, Oxford Handbook of Evolutionary Psychology, pages 669-681. Oxford University Press.

Maynard-Smith, J. and Szathmáry, E. (1997). The Major Transitions in Evolution. New York: Oxford University Press.

Szathmáry, Eörs & Szabolcs Számadó (2008): Being Human: Language: a social history of words Nature 456, 40-41.

Tomasello, Michael (2008): The Origins of Human Communication. Cambridge, MA; London, England: MIT Press.

Perspective, Language Evolution & Genes

As I wrote in my last post, according to Edmund Blair Bolles, evolang08 can be seen as an all-out attack on the Chomskian paradigm. Whereas Bolles’ thinks that the downfall of the Chomskian paradigm is near, I am more skeptical. Of course, many of the talks at evolang08 seem to have dealt severe blows to general conceptions of Chomskyan linguistics, but given that the field of language evolution studies was opposed to many of Chomsky’s ideas from the start, this seems a natural development.

So will the Chomskyan Paradigm simply go extinct in the sense of Kuhn’s (1962) “Structure of Scientific Revolutions”? Clearly in this field people like Juan Uriagereka are in the minority, and this speaks for the diminishing influence of some Chomskian ideas, especially ‘syntactocentrism’, i.e. the idea that "that it is 'as if syntax carved the path interpretation must blindly follow.'" (Chomsky 2007: 24) in general, but on the whole I think that the Chomskyan research paradigm is alive and well, speaking in terms of ‘believers’, as Derek Bickerton (2008) puts it, in the generative enterprise.

EBB himself writes that: “It is only the odd ones among them who are interested enough in the evolution of language to even think of attending such a conference, but the absence of all the leaders of the effort to understand the evolution of generative grammar—Steven Pinker, Marc Hauser, Tecumseh Fitch, Ray Jackendoff, and Paul Bloom — cannot be entirely a coincidence.”

An example of biologically informed research in linguistics – Biolinguistics – in the Chomskyan tradition is the open access journal with the same title which was inaugurated in 2007 and whose second issue appeared this week. The second issue features two very cool papers.

The first, by Boban Arsenijević (2008), of whom I must admit I’d never heard before, is about how we got “From Spatial Cognition to Language.” Arsenijević argues that cognitive mechanisms for spatial computation switched from domain-specific to a domain-general non-spatial use, enabling the production of generative conceptual structures, i.e. complex kinds of displaced concepts which could be located in some kind of ‘cognitive map’ which weren’t inextricably bound to a spatial situation anymore, but instead became a ‘decoupled representation’ (Sterelny 2003).

This cool proposal is also consistent with Brian MacWhinney’s “Perspective Hypothesis”, which argues that: Perspective taking is an essential property of human communication and higher-level cognition, and that

"1. Perspective taking operates online using images created in five systems: direct experience, space/time deixis, plans, social roles, and mental acts.

2. Language uses perspective taking to bind together these five imagery subsystems.

3. Grammar emerges from conversation as a method for supporting accurate tracking and switching of perspective.

4. By tracing perspective shifts in language, children are able to learn the cognitive pathways and mental models sanctioned by their culture.“ (Macwhinney 2005: 198)

I would argue that we can visualize this new representational perspectival format with Bühler’s (1934) ‘coordinate system of subjective orientation’, i.e. as a systemic space (Köller 2004) which through communication is made available to both interlocutors, becomes a shared, ‘mutually manifest’ (Eilan 2005) representation.

Similarly, in a paper for evolang 08, Benôit Dubreuil argues that the key shift to modern human behavior, such as language and other shared symbolic artifacts, was a “domain-general cognitive change”, namely “the capacity to fully represent the point of view of other, what psychologists call ‘level-2 perspective-taking’” (see, e.g., Flavell 1988).

There is another really cool paper in this issue of Biolinguistics called “Languages and Genes: Reflections on Biolinguistics and the Nature–Nurture Question” by D. Robert Ladd, Dan Dediu & Anna R. Kinsella of Edinburgh University. Ladd & Dediu published a really cool paper in the Proceedings of the Academy of Sciences in 2007 (Dediu & Ladd 2007), in which they described their two genes related to brain growth and development, ASPM and Microcephalin, which show signs of relatively recent natural selection and exist in a more recent (ASPM -D; about 5,800 years old, and MCPH-D, about 37,000 years old) and an older form (ASPM, MCPH).
It turns out that the geographical distribution of these genes is highly correlated with whether people speak tonal languages (like Chinese) or non-tonal languages (like English). In general, populations speaking tonal languages possess the older forms, and populations speaking non-tonal languages have the D (for derived)-versions of the genes, though there of course are exceptions and cases of contamination. In their present paper Ladd et al. (2008) discuss the importance of genetic findings for the linguistic theory. They clarify that they

“are not proposing any sort of deterministic relation between genes and language, only a very indirect and probabilistic one; we certainly are not suggesting that there are 'genes for Chinese'. But we believe that the broad outlines of an explanation based on the interaction of bias and cultural transmission are very plausible indeed“ (Ladd et al. 2008: 118).

They also argue against the notion that the linguistic effects of ASPM-D and MCPH-D were the driving forces of the genes’ natural selection, but rather see them as selectively neutral side-effects, as there are no obvious differences between tonal and non-tonal languages in regards to biological fitness, as both are equally suited to support and scaffold all sorts of varieties of complex human behaviors. (Ladd et al. 2008: 120)
To take an example, in the time of early skyscraper-building in America, a lot of the construction workers were Mohawks, because they were free from giddiness. And although the modern urban environment was completely different from that of their own homes, as were the affordances of steel construction work, they constantly used their native language to communicate about their work, had absolutely no problem to adapt their linguistic output to this new world, and even taught some of their co-workers their language to facilitate communication.

In all, Ladd et al. (2008) propose to move beyond dualistic nature or nature-view and take seriously the fact that

"there is a fundamentally complex and irreducible interaction between one’s genes and one’s language and culture — between nature and nurture” (Ladd et al. 2008: 120).

As an example they cite the recent finding that breastfeeding can indeed have positive effects on a baby’s IQ, but only if she possesses a certain variant of the FADS2 gene (Caspi et al. 2007, Ladd et al. 2008: 120f.).

In their view this also raises problems with static generativist views of language capacities as a perfect system, because from an evolutionary point of view, it makes much more sense to treat language competency as a complex dynamic system, which instead is “diverse and dynamic” and constantly changing on the timeline of both cultural transmission as well as individual development (Ladd et al. 2008: 121).

Ladd et al. see their results on the genetic influences “on typological linguistic features” as being in favor of the claim that there are innate linguistic ‘biases’, “deep cognitive, and ultimately genetic, causes” (Ladd et al. 2008: 121) of some properties of language, thus supporting the Chomskyan research paradigm in some ways. However, they also remark that

“Linguistic theorizing in general, and biolinguistics in particular, must take into account and integrate the idea that human linguistic capacities are variable and probably still evolving" (Ladd et al. 2008: 121).

Moreover, they are also opposed to Chomsky’s stance on the evolution of language, which he renewed in the first issue of Biolinguistics (Chomsky 2007), in which he wrote that:

"The core principle of language, unbounded Merge, must have arisen from some rewiring of the brain, presumably the effect of some small mutation” (Chomsky 2007: 22).

And that this property yielded

“a language of thought, later externalized and used in many ways” (Chomsky 2007: 24).

In contrast, Ladd et al. hold that

“language has evolved through the standard mechanisms of evolutionary biology, in a gradual manner, and that it continues to do so” (Ladd et al. 2008: 122).

In my next post I’ll come back to Chomsky’s position on these issues and some neuroscientific evidence that argues against it.

References:

Arsenijević, Boban (2008): From Spatial Cognition to Language Biolinguistics 2.1, 3–23.

Bickerton, Derek (2008): Bastard Tongues: A Trailblazing Linguist Finds Clues to Our Common Humanity in the World's Lowliest Languages. New York: Hill and Wang

Bühler, Karl (1934): Sprachtheorie: Die Darstellungsfunktion der Sprache. Stuttgart: Fischer.

Caspi, Avshalom, Benjamin Williams, Julia Kim–Cohen, Ian W. Craig, Barry J. Milne, Richie Poulton, Leonard C. Schalkwyk, Alan Taylor, Helen Werts & Terrie E. Moffitt. (2007) Moderation of breastfeeding effects on the IQ by genetic variation in fatty acid metabolism. Proceedings of the National Academy of Sciences of the USA 104, 18860-18865.

Chomsky, Noam (2007): Of Minds and Language. In: Biolinguistics 1, 9-27.

Dediu, Dan & D. Robert Ladd. (2007) Linguistic tone is related to the population frequency of the adaptive haplogroups of two brain size genes, ASPM and Microcephalin. Proceedings of the National Academy of Sciences of the USA 104, 10944-10949.

Eilan, Naomi (2005): Joint Attention, Communication, and Mind. In: Naomi Eilan, Christoph Hoerl, Teresa McCormack und Johannes Roessler (Eds.): Joint Attention: Communicationd and Other Minds. Oxford: Clarendon Press (Issues in Philosophy and Psychology), 1-33.

Flavell, John H. (1988): The Development of Children’s Knowledge about the Mind: From Cognitive Connections to Mental Representations. In: Janet W. Astington, Paul L. Harris und David R. Olson (Eds..): Developing Theories of Mind. Cambridge: Cambridge University Press, 141-172.

Kuhn, Thomas S. (1962): The Structure of Scientific Revolutions. Chicago: University of Chicago Press.

Ladd, D.Robert, Dan Dediu & Anna R. Kinsella (2008): Languages and Genes: Reflections on Biolinguistics and the Nature–Nurture Question. In: Biolinguistics 2.1, 114–126

MacWhinney, Brian (2005): The Emergence of Grammar from Perspective. In: Diane Pecher und Rolf A. Zwaan (Eds.), The Grounding of Cognition: The Role of Perception and Action in Memory, Language, and Thinking. Cambridge: Cambridge University Press, 199-223.

Sterelny, Kim (2003): Thought in a Hostile World: The Evolution of Human Cognition. Malden: Blackwell.

A Zombie’s Inquiry Into the Evolution of His Most Favorite Meal IV: Genes that Code for Tasty brains

There are two main approaches to look at the differences between humans and other non-human primates such as chimpanzees: ethological studies of animal behavior and their cognitive abilities (it looks like there is a difference between Cognitive Ethology, Comparative Ethology & Comparative Psychology, but as it seems this is more a matter of whether you emphasize the biological, cognitive science, or psychological aspect of behavior) and genomic comparisons.

On the side of genetic comparisons, we already have the sequenced genome of humans, chimpanzees, and macaques, which, somewhere in the relatively near future, the future, are to be joined by the genomes of Neanderthals, bonobos, (both sequenced by our friends at the Max Planck Institute for Evolutionary Anthropology - gosh! it would really have been a tremendous loss for science if its members had been eaten by zombies… So thanks for that George) gorillas, and gibbons. As Kambiz Kamrani pointed out over at primatology.net, the more primate genomes we get together, the better we are able to make out human specialness (as well as Chimpanzees-Specialness, Bonobo-Specialness, Gorilla-Specialness etc.), as well as the things we share with other primates, in terms of specific genes.
This may indeed help us ““to find out what being human is.” James Watson originally hoped this would be the result of the sequencing of the human genome. (Pennisi 2007: 218) but now, with an ever-growing genetic database, we somewhere in the future we may indeed be able “to trace back the evolutionary changes that occurred at various time points, leading from the common ancestors of the primate clade to Homo sapiens,” as Bruce Lahn puts it. (Pennisi 2007: 218). Researchers all over the world further plan on sequencing the genomes of the orangutan, the marmoset, the tarsier, the mouse lemur, the galago, the tree shrew as well as the lemur in order get an ever broadening picture of our evolutionary history, ultimately tracing back 83 million years of evolutionary time.
Within this comparative context, we of course may really see the “dawn of cognitive genetics” (Pinker 2001: 465). In the field of language evolution, for example, we may finally establish the genetic foundations and extensions that made human language possible. But at the moment, it seems as if there are still so much things that are maddeningly unclear, (and I as layman, naturally don’ understand anything about “regulatory sequences”, “junk DNA” and messy genetic differences at the molecular level…) so it’s definitely still a very long way until we can go beyond FOXP2, MPH1, and ASPM (not to speak of understanding even the exact roles of these genes.)

On the side of ethological studies, the methods employed and results obtained (which I describe in my last post) by Herman et al. (2007) clearly show interesting avenues of future research, and hint at a possible meeting point between the two approaches:

“A major avenue of future research is thus to use [the research methodologies employed by Herman et al.] to characterize the behavioral-cognitive phenotype of a wide variety of primate species. This could be done through systematic testing of carefully chosen representatives of the more than 50 genera of primates, which should then enable us to map out cladistically the evolution of primates’ most important cognitive skills at the level of both the phenotype and, ultimately, the genotype.” (Herman et al. 2007: 1365)

For our Zombie-Scientist George the main question remains: “Why are human brains so tasty ?” (let’s presume that in our Parallel zombieverse, the zombie-gourmet is only fond of human brains and not that of other non-human brains.) The Theory by which George now arrives looks like this: “The unique tastiness of human brains basically must boil down to some uniquely human genes (or genetic combinations or gene expressions)” That’s why I will lok a bit at the differences between human and chimp-genes in my next post.

References:

Hermann, Esther Josep Call, María Victoria Hernández-Lloreda, Brian Hare, and Michael Tomasello. 2007. “Humans Have Evolved Specialized Skills of Social Cognition: The Cultural Intelligence Hypothesis” Science 317: 1360-1366.

Pennisi, Elisabeth. 2007 “Genomicists Tackle The Primate Tree.” Science 316: 218-221.

Pinker, Steven. 2001. “Talk of genetics and vice versa“ Nature 413: 465-466