How Language Evolved
Domestication explains how biology and culture interact for evolving language.
Posted Sep 03, 2018
Why humans have language and why other animals lack it is one question that has intrigued people since forever, and many scientists too, from anthropologists to neuroscientists to linguists. Over the years, a sound story of how language evolved in our species has eventually crystallized, mainly after the Chomskyan revolution in the sixties, which put the focus on the brain, as the place where language is located, and abandoned the idea of language as a cultural object. This story can be summarized as follows. Although primates—and plausibly extinct hominins like Neanderthals—are able to communicate with their conspecifics (using sounds and gestures), they lack language. Language is the cognitive ability that enables us to combine ideas in our minds and to map them into strings of sounds to be shared with others. Because this is a human-specific ability and because it is located in the brain, some crucial event (perhaps as a result of a gene mutation) rewired the primate brain and allowed this new ability to emerge. Other components of language, like speech organs, seemingly have a longer evolutionary history, but they are secondary to language. The corner stone of language is this ability to combine concepts (and words) recursively. And only we have it, paraphrasing a famous recent book by Noam Chomsky and Robert Berwick.
Once we had a modern, language-ready brain, modern languages (like the ones we speak today) instantaneously emerged. This is also a uniformitarian view of languages, that assumes that there are not such things as primitive or simpler languages. Because all humans have similar brains and are endowed with similar cognitive capacities, all human languages are expected to exhibit similar features and to be equally complex. And because core features of languages (like syntax) are claimed to result from brain properties, languages are expected to be insensitive too to external factors, like the physical environment or the culture, which are pretty variable.
Nowadays, many scientists have serious doubts about the reliability of this story, and particularly, about the hypothesis that the emergence of our species automatically brought about the emergence of modern languages. On the one hand, (paleo)anthropological findings suggest that the human skull went on changing after our split from Neanderthals. Accordingly, we cannot rule out the possibility that these changes resulted in differences in brain structure and function, and ultimately, in cognitive abilities important for language. On the other hand, there is increasing evidence that the environment (climate, orography, vegetal coverage) and the cultural milieu (social networks, interaction with speakers of other languages) do affect language structure, from sounds to morphology to syntax. I discussed these effects in detail in two related posts (here and here). Summarizing what I wrote then, there is evidence that modern languages were also the result of cumulative changes linked to the human-made niche via cultural evolution.
In this post I wish to present the hypothesis that human self-domestication (that is, the existence in humans of features of domesticated mammals compared to wild primates) contributed to both processes, providing a good rationale of when, how, and why language evolved in our species (of course, building on ancient biological and cognitive components) and modern languages appeared in our history. In my opinion, the following can be a plausible account of the whole process.
After our split from Neanderthals, some gene mutations resulted in a brain rewiring that habilitated a new neuronal workspace that entailed enhanced cognitive abilities, particularly the ability to merge concepts and create new concepts without real correlates. In other words, these mutations brought about our language-readiness, that is, our species-specific ability to learn and use languages, that we put into use whenever we grow in a suitable environment (surrounded by, and interacting with other people). As a result of different factors, mostly related to sexual selection, we were progressively self-domesticated via selection against aggression (for example, if less aggressive men had a higher reproductive fitness and/or were preferred by women because they were more involved in child care). In turn, this might be explained by changes in social networks and/or population densities as a result of changes in climate, food supply, and the like. In any case, the important issue is the consequences derived from self-domestication. On the one hand, because candidate genes for domestication are functionally related with candidate genes for language-readiness (as we show here), self-domestication might have contributed to the brain remodeling underlying our language-readiness. However, because of this functional connection, the changes that contributed to our language-readiness might have contributed as well to our self-domestication. This is shown in the next figure.
On the other hand, self-domestication seemingly favored the cultural transmission process that allowed the exploitation of the full cognitive potential of our language-ready brain and ultimately, fueled the sophistication of linguistic structures via a cultural process. Hence, the less aggressive behavior and the neotenic features (that is, an extended juvenile period) associated with domestication seemingly resulted in enhanced intergroup contacts, more complex social networks, prolonged childhood, and enhanced play behavior (see the figure above). As we have discussed in a recent paper, all these changes might have resulted in the creation of a niche that afforded richer linguistic interactions and that facilitated learning through teaching and experimenting. These are important prerequisites for mastering complex linguistic systems of the sort we find in languages like English or Chinese, which are endowed with expanded vocabularies and complex syntax (see my posts on prehistoric languages for details)
In summary, my view of how language (and languages) might have evolved is as follows: after our split from Neanderthals, our brain/cognition was not a fully modern one, and neither was our behavior, in part, because we were not fully self-domesticated yet. Subsequent changes in our brain (globularization of our skull/brain), cognition (language-readiness), and behavior (enhanced sociability and parenting behavior) occurred gradually, as self-domestication enhanced. Overall, this resulted in the emergence of a modern-like brain and cognition, and a modern-like behavior, around 100-50 kya, and ultimately, of modern-like languages, mostly as a result of cultural changes in a favorable learning/teaching environment.