By Cedric Boeckx, University of Barcelona
During the course of evolution, our brain got ‘language-ready’ — that is, ready to construct and then put to use grammatical systems that appear to be too complex for other species to master. But what property of our brain makes it language-ready? None of the leading candidates can account for an aspect that is common to all languages: the ability to combine and recombine mental units that belong to distinct cognitive domains. (The brain has many cognitive domains: each is a different circuit of the brain specialized to deal with one aspect of the world around us.)
Paul Broca was the first to notice that when a particular area of the brain is damaged, the result is impaired language ability. That area of the brain is referred to as Broca’s area. Broca also noted that the two halves of the brain, the left half and the right half, are not symmetrical. Building on Broca’s writings, it is believed that this asymmetry is a characteristic of the language-ready brain: prominent asymmetries are indeed found in the gross anatomy of the brain in anatomically modern humans. However, the roots of this lateral asymmetry have been traced to our primate inheritance. Secondly, other non-primate vocal learners, such as songbirds, also show hemispheric asymmetries; perhaps such asymmetry is a result of the communicative function played by language and not its cause. I believe that the answer lies elsewhere, in another anatomical characteristic of our brain that may be the key to our language-readiness.
A detailed examination some ten years ago of fossilized skulls of the genus Homo revealed another feature of modern humans — a feature not found in the Neanderthals, who also had well-developed brains. In the Neanderthals, the brain case was flatter and elongated; in modern humans, it is more rounded or spherical. Subsequent research showed that a spherical skull, or brain case, is the result of a unique developmental path in modern humans, and it is formed at that stage of growth at which the brain is developing and shapes the skull. The skull is flexible enough at that stage to accommodate the shape of the growing brain. In other words, the container changes its shape to fit the contents. The skull is indeed a bit like a balloon or a tyre tube that expands as more and more air is pumped into it.
What has a spherical brain to do with language? I am exploring the idea that anatomical structures at the centre of a spherical brain occupy a privileged position. One such anatomical structure is the thalamus. Although the thalamus has been linked to many human-specific traits such as intelligence or consciousness, its role in language has not been fully explored. Yet, if a key function of language is to link units from different cognitive domains, presumably distributed widely across the brain, the thalamus is certainly well placed for it. We should seriously consider the possibility that the thalamus is the conductor in a large orchestra, coordinating the actions of many players (represented by different cortical zones) and synchronizing and fine-tuning their activities.
My collaborator Antonio Benitez-Burraco and I have noted with interest that some of the genes — RUNX2, for example — responsible for those physical characteristics of our species that set us apart from our close cousins, namely the Neanderthals, directly influence the way the thalamus grows and connects with the rest of the brain. Focusing on our spherical brain case and the factors that decide its shape may shed some light on one of our most distinctive mental attributes.
Cedric Boeckx
Catalan Institute for Advanced Studies (ICREA)
University of Barcelona
www.atomiumculture.eu
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