Prehistoric Languages… and Prehistoric Minds? Part II

In my previous post I wrote about different tools and approaches that could help gain a better knowledge of prehistoric languages, ranging from linguistic theory to ecology. We expect them to illuminate the huge time window of roughly 190.000 years of language change that is essentially opaque to the traditional methods employed by historical linguistics. But as I also said, we have assumed that the human brain has remained the same since we emerged as a differentiated species. This is a core assumption of those who believe that biological evolution has nothing to say about linguistic change, like Chomskyan linguists. According to their view, prehistoric languages were similar to present day languages because they were the product of a modern brain. But it is also the assumption of those other who believe that the environment had some effect in shaping the languages we speak. According to their view cognitive modernity emerged first, and only later language started to gain complexity with time.

Where the Pirahã live...

Source: Dixon & Aikhenvald (1999): "Other small families and isolates" in The Amazonian Languages. By Davius (Own work) [Public domain], via Wikimedia Commons

Whereas the former is a robust hypothesis, the latter is an interesting view too. It entails that human beings exploit their cognitive potential differently according to the different environments where they live. You may remember from my post the Pirahã people from the Amazonian forest. Now we are pretty sure that they can understand and use recursive structures (so they are cognitively modern). After all, they can learn languages like Portuguese in which you find lots of embedded sentences. But even if their language was proved to lack real recursion, this could only mean that they don’t produce complex sentences (so they use a simpler language) because they don’t need them. Under this view, some aspects of language evolution are expected to rely on cultural evolution and to be triggered by environmental cues. This hypothesis is also of interest for prehistorians and archaeologists, because confident remains of present-day behaviour (like art) appeared quite later in our history, more than 100.000 years after our origins. Perhaps you need a sophisticated language to convey the sophisticated ideas and know-hows needed for painting, sculpting female figurines, or transforming your hunter-gatherer society in a post-industrial society. Or perhaps it is not necessary, but complex languages still confer some subtler advantage.

Evidence of modern behaviour in Africa. Roughly 100.000 years ago most of present-day complex behaviours started to appear.

Source: McBrearty, S. y Brooks, A. S. 2000: “The revolution that wasn’t: a new interpretation of the origin of modern human behavior”. Journal of Human Evolution 39: 453-563 (figure 13)

In my own research I have extensively studied the origins of cognitive modernity (entailing a modern faculty of language). As I reasoned in this paper, I believe that our mode of cognition is human-specific and it may have been brought about by a set of coordinated changes in the hominin skull/brain, which favoured new patterns of neuron interconnection across the whole brain that habilitated a new neuronal workspace. As I have also shown in several related papers (here, here and here), the involved genes show differences with Neanderthals and Denisovans regarding their regulatory regions, their coding regions, and/or their methylation patterns. This does not entail that other hominins lacked language or even speech. It only means that very probably they had a different mind, a different faculty of language, and a different way of communicating their thoughts.

The three set of genes related to the globularization of the human skull/brain. See Boeckx and Benítez-Burraco 2014a,b and Benítez-Burraco and Boeckx 2015 for details.

Source: Antonio Benítez-Burraco

Interestingly, the real story may be more complex. The retrieval of ancient genomes has revealed that changes in several genes involved in brain function have been fixed well after our split from Neanderthals and Denisovans, and before the diversification of the human branches, as showed by Zhou and colleagues. We know that mutations in some of these genes impact on our cognitive abilities, like executive function, abstract reasoning, spatial and episodic memory, or verbal speed performance. Moreover, they are found mutated in people with Alzheimer’s disease or Parkinson’s disease. And some of these genes are important for brain connectivity. One wonders whether these changes that were fixed later in our history contributed to refine our cognitive abilities. We don’t know (yet), but it is a real possibility.

Timeline of positive signals in modern humans.

Source: Zhou et al. 2015. http://biorxiv.org/content/early/2015/06/19/018929 Figure 4a

Titlepage of Darwins' book

Source: [CC BY 4.0 (http://creativecommons.org/licenses/by/4.0)], via Wikimedia Commons

Additional evidence that our cognitive abilities may have differed (slightly) from those of early modern humans concern the intriguing process of domestication. Many animal species have been domesticated over the years by human beings. Interestingly, most of the domesticated mammals share a set of common traits, like reduced brains, changes in the orofacial region, or a less aggressive behaviour. Intriguingly, when we compare modern humans with extinct hominins like Neanderthals we find that many of these domesticated traits are present in our species and absent in them. Darwin himself wrote about human beings as domesticated primates in his book The Descent of Man.

Song complexity in domesticated white-rumped munias is greater than in wild munias

Source: By Shantanu Kuveskar (Own work) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons

But why did human beings become domesticated? Or better, self-domesticated, because no one never tamed us. Well, self-domestication could be an adaptation to the human-made environment, or a by-product of mate-choices, or a product of selection against aggression and towards social tolerance. But, as I reasoned in this paper, it may have been as well a by-product of the same changes that brought about our distinctive mode of cognition. The reason is that the candidate genes for these changes are also found among (and interact with) the candidates for domestication.

Interestingly, domestication can trigger complexity. For instance, domesticated songbirds like the white rumped munias learn and perform songs that are more diverse and more complex than those observed in their wild conspecifics. The reason is that domestication entails a relaxation of the selective pressures on the animals (after all, if you live in a secure environment you don’t care if your elaborated songs attract predators). Many authors have claimed that the same holds for human language. Accordingly, domestication would have provided our species with the cultural niche that favoured the emergence of complex languages through a cultural process. A secure (domestic) environment provides the child with an extended socialization window which enables her to get a greater amount of triggering linguistic stimuli, to interact more time and more intensively with other conspecifics, and to experiment with language for a longer time. And this is the perfect environment for moving from pidgin-like languages to more sophisticated languages.

But the story is even more interesting. In a series of great posts (here and here), Christopher Badcock has summarised our recent research on domestication, language impairment, and language evolution. As Christopher correctly claims, some present-day, human-specific pathological conditions impairing cognitive capacities that are important for language acquisition (like inferencing or metaphoric processing) and entailing problems with language can be linked to an abnormal self-domestication of our species. For instance, people with autism exhibit higher brain volumes, which correlate with lower functioning abilities, plausibly because brain overgrowth impacts on networking efficiency among widespread regions of the cortex. Likewise, whereas domestic mammals typically show a smaller amygdala and a reduced size of other components of the limbic system, people with autism exhibit increased volumes of the amygdala, which correlate with the severity of their social and communication impairment. And higher amygdala volumes are associated with poorer language abilities during infancy also in the typically-developing population.

The abnormal presentation of the "domestication syndrome" in autism

Source: Benítez-Burraco et al. 2016 figure 1

Interestingly, this process of self-domestication may be still ongoing. Present-day humans exhibit smaller brains from the last 40.000 years and this reduction in brain size has been related to the domestication hypothesis by some researchers like Bednarik. In domestic animals their smaller brains tend to reorganize adaptively in response to the domestic environment For instance, homing domestic pigeons exhibit proportionally larger hippocampus and olfactory bulbs, plausibly because of their enhanced spatial cognition and sensory integration. Likewise, domestic guinea pigs show enhanced spatial learning abilities compared to their wild conspecifics. Not surprisingly, domestication entails an enhanced sensibility to human social cues and an improved ability to solve problems relying on such cues. We don’t know which cognitive modifications (if any) were brought about by the recent brain reduction observed in late modern humans. But there is no special reason why human brains should behave differently to animal brains. If so, some cognitive differences with early modern humans are expected. The corollary is that language change in the remote past could have proceed (slightly) differently than in present day societies.

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In my last post I quoted Chomsky’s claim that language is a mirror of the mind, in the sense that the analysis of the linguistic structures found in a language illuminates how the mind works. But languages also reflect the way in which human beings live. Knowing more about the languages spoken in the deep past will improve our understanding of how our distant ancestors lived, behaved, and thought. And vice versa. Knowing more about the environment in which they lived and about how their brain was built will enable us to gain a more accurate view of the languages they spoke. In my opinion, several lines of research could help improve this knowledge. First, studies aimed to compare the cognitive abilities exhibited by wild and domestic varieties of the same species, particularly those comparing wild primates and humans (e.g. chimps vs. bonobos vs. humans). Second, comparative studies of the molecular signature of domestication and its effect on the brain in different mammal species (e.g. dogs vs. cats vs rabbits, etc.). Third, comparative studies of the signatures of domestication in pathological conditions involving an abnormal mode of cognition and entailing language deficits (e.g. autism vs. schizophrenia).

But we have had enough with our own species. In a future entry I will post about the faculty of language other hominins might have been endowed with. Our closest extinct relative, Neanderthals, will be the focus of inquiry.