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Leading Evolutionary Scientists Admit We Have No Evolutionary Explanation of Human Language

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Denyse O'Leary has written here about the difficulty that evolutionary psychology faces in explaining the origin of language. Indeed, back in May, a group of huge names in evolutionary biology, evolutionary anthropology, and evolutionary psychology published a peer-reviewed paper in the journal Frontiers in Psychology admitting that in fact we have no explanation for the origin of language. The abstract strikingly states:

Understanding the evolution of language requires evidence regarding origins and processes that led to change. In the last 40 years, there has been an explosion of research on this problem as well as a sense that considerable progress has been made. We argue instead that the richness of ideas is accompanied by a poverty of evidence, with essentially no explanation of how and why our linguistic computations and representations evolved. We show that, to date, (1) studies of nonhuman animals provide virtually no relevant parallels to human linguistic communication, and none to the underlying biological capacity; (2) the fossil and archaeological evidence does not inform our understanding of the computations and representations of our earliest ancestors, leaving details of origins and selective pressure unresolved; (3) our understanding of the genetics of language is so impoverished that there is little hope of connecting genes to linguistic processes anytime soon; (4) all modeling attempts have made unfounded assumptions, and have provided no empirical tests, thus leaving any insights into language's origins unverifiable. Based on the current state of evidence, we submit that the most fundamental questions about the origins and evolution of our linguistic capacity remain as mysterious as ever, with considerable uncertainty about the discovery of either relevant or conclusive evidence that can adjudicate among the many open hypotheses.

(Marc Hauser, Charles Yang, Robert Berwick, Ian Tattersall, Michael J. Ryan, Jeffrey Watumull, Noam Chomsky and Richard C. Lewontin, "The mystery of language evolution," Frontiers in Psychology, Vol 5:401 (May 7, 2014) (emphases added).)

It's difficult to imagine much stronger words from a more prestigious collection of experts. But what about all of those news stories about apes who learn how to communicate using sign language? Do they show that apes possess or can learn some primitive precursor to humanlike language? No, they say:
Talking birds and signing apes rank among the most fantastic claims in the literature on language evolution, but examination of the evidence shows fundamental differences between child language acquisition and nonhuman species' use of language and language-like systems. For instance, dogs can respond to a few hundred words, but only after thousands of hours of training; children acquire words rapidly and spontaneously generalize their usage in a wide range of contexts. Similarly, Nim Chimpsky, the chimpanzee that produced the only public corpus of data in all animal language studies, produced signs considerably below the expected degree of combinatorial diversity seen in two-year old children, and with no understanding of syntactic structure or semantic interpretation. Though these studies are of potential interest to understanding the acquisition of specialized, artificial skills -- akin to our learning a computer language -- they do not inform understanding of language evolution.
They conclude: "For now, the evidence from comparative animal behavior provides little insight into how our language phenotype evolved. The gap between us and them is simply too great to provide any understanding of evolutionary precursors or the evolutionary processes (e.g., selection) that led to change over time."

But what about FOXP2 -- a gene that seems to be connected to language, where humans have a couple of unique amino acid differences compared to nonhuman primates? In The Language of God, Francis Collins presented FOXP2 as something of a miracle mutation that could have caused human language to develop (see pp. 139-141). Time Magazine once claimed that our two amino acid differences in this gene could have caused "the emergence of all aspects of human speech, from a baby's first words to a Robin Williams monologue." These authors would disagree, because, as they point out, we aren't even sure exactly how FOXP2 affects language:

FOXP2 is a transcription factor that up- or down-regulates DNA in many different tissue types (brain, lung, gut lining) at different times during development as well as throughout life. This broad functional effect makes evolutionary analysis difficult. In particular, the exact mechanisms by which FOXP2 mutations disrupt speech remain uncertain, variously posited as disruptions in motor articulation/serialization in speech, vocal learning generally, or broader difficulties with procedural serialization. This is critical because FOXP2 mutations may disrupt only the input/output systems of language, sparing the more internal computations of human language syntax or semantics; or it may be that FOXP2 affects general cognitive processing, such as general serial ordering of procedures. Second, it is not clear whether the amino acid changes distinguishing FOXP2 in humans and nonhumans represent adaptations "for" language, since their functional effects remain unclear. One of the two protein-coding changes along the lineage to modern humans is also associated with the order Carnivora. Since FOXP2 also targets the gut lining, this evolutionary step may have had little to do directly with language but instead with digestion modifications driven by forest-to-savannah habit and so dietary change...
According to the paper, claims that mutations in FOXP2 explain the origin of language cannot be true because, as the authors put it, "we lack a connect-the-dots account of any gene to language phenotype."

Of course the authors propose various avenues of research that they think might someday lead to an understanding how language arose. But for the present, their analysis is discouraging: "Until such evidence is brought forward, understanding of language evolution will remain one of the great mysteries of our species."