A minor role for genetics in language evolution

In their paper, Benitez-Burraco & Barcelo-Coblijn (BB & BC, this Forum) make an in-depth analysis of hominin interbreeding -par-ticularly, the presence of Neandertal DNA in anatomically modern humans (AMH)-, and raise the question of its relevance in language evolu-tion. While different arguments are possible in this regard, the simplest way to set the lines is to consider “early” and “late” language evolution scenarios. “Early” scenarios of language evolu-tion contend that language appeared early in the hominin lineage (so that the species in the lineage were all able of language). “Late” scenarios con-tend that language is a synapomorphic feature of our species and so consequently appeared after the separation of the Neandertal species.Genetic interbreeding between Sapiens and Neandertals prima facie challenges the “late” scenario, according to which language is a “human only” feature which evolved after the split between the two species. If it turns out that such a split was not decisive, or irreversible, since interbreeding was not just possible, but even common, then the idea that language is a late acquisition, linked to the appearance of AMH as a new species, seems to loose support, while the view that Neandertals had the same linguistic abilities as AMH because they were already avail-able to a common ancestor, seems to be more plausible. In fact, the very possibility of inter-breeding might even call into question the idea of a “speciation event”, and the well-established assumption that AMH and Neandertals are two different species, rather than just two groups of the same species. since the possibility of inter-breeding is constitutive of a common species, while reproductive isolation is required to estab-lish a new species.However, this is not the strategy adopted by the authors of the paper we are commentting on. BBB b) sharing genes is not enough to make sure that those genes are expressed the same way in both species, because this depends on many other genetic changes; and finally, c) that the linguis-tic phenotype is not determined by the linguistic genotype, because of the importance of develop-ment in the acquisition of language. In our view, the third argument is the strong-est, and, when properly developed, it preempts the other two. Put in another way, it seems to us that the authors give the finding of genetic interbreeding more weight than it deserves, just because they assume -along with the explosion of interest in the search for “language genes”-, that there can be such a thing as “the linguistic genotype”. While it is obvious that any human mental capability requires a genetic make-up as long as it is a biological phenomenon, it cannot be simply assumed that there is going to be some part of the genome specialized for every mental faculty, or for language in particular. Not only because genes can be pleiotropic (i.e., involved in very different processes), but also because they don’t work in isolation (their effects very much