Wednesday, February 9, 2011

The Symbolic Species: The Co-evolution of Language and the Brain

by Terrence W. Deacon

In answer to central questions such as "What makes humans different?", "Is it brain size that gives humans speech?", "How did consciousness and language evolve in humans?", and "What is consciousness?", Deacon provides an elegant solution. We are a symbolic species. Language, and as a consequence consciousness, are made possible by the use of an ability to process symbols. I will try to explain how the symbolic process works, why it is important, how it evolved, and what effect it has on consciousness following Deacon's arguments.

Let us make a few important points to start with. The approach here is truly inspirational and revolutionary. This is not a repetition of tired and discredited views of 'language areas of the brain' or the left-right split for thought and language. This book does not spend 450+ pages supporting the tired hackneyed conjecturing of Chomsky, Pinker & their followers. Ever since Chomsky first announced some kind of language acquisition device, more and more physical evidence has been amassed about how the brain functions and is structured to show how misguided the original idea was. Instead of retreating, the Chomsky camp has only tried to obscure this basic belief behind formalisms and frauds. Deacon puts the problem clearly. It is nonsense to talk about brains being specifically designed to cater to language from birth, as if language is fixed and brains change to suit language. Whatever language is, it must have evolved to cater to the proclivities of human brain structures and patterns. Language has evolved to the human brain, not the other way.

The core principle of Deacon's approach is a neo-Piercean symbolism. While a real-life object may have a referent, the referent can quickly become an icon that stands separately from the object itself. In the animal world, alarm calls have a direct relationship between a threat and the sound made by a group of animals. These references rarely become iconic in the way that a pet dog may be able to associate any kind of round object with the sound of 'ball' and behave accordingly. None of these, however, represent the way that humans use language. The extra step that animals do not seem to make is to then re-associate icons with each other in novel combinations to the extent that meaning is derived more from the relationships between icons than between the icon and the original object. That this ability is not beyond animals, in particular bonobos, has been demonstrated by the great work carried out by Sue Savage-Rumbaugh and colleagues at the Great Ape Trust, referred to by Deacon.

The question that we must answer is why humans have come to depend so heavily on symbols. Or, more precisely, what evolutionary advantage did symbolic thinking offer early humans? To answer this question Deacon suggests that to look for the source of humans' unique linguistic abilities we should look at their unique evolutionary adaptations. Fundamentally, human societies are all WRONG for two reasons. The first is that human growth patterns work against survival. At precisely the time that mothers and infants need the most food they are at their most incompetent at foraging and feeding. The only way that the mother and child can be assured of having enough food is to share with others, either with other potential mothers or with the father. Potential mothers must make the symbolic connection between exchanging food in their hand for a promise of assistance when they are in need. Thus reciprocity, a human cultural universal, is a symbolic act - it is an exchange of material goods for a promise. Even animals capable of symbolic reasoning find this a difficult leap to make. A father will only share food if he is certain that the child is carrying their genes - and this leads us to the 2nd reason why human societies should not really work when compared to other animals' responses to the reproduction of an individual's genes. Typically animals will either pair-bond or congregate in exclusive mating groups. That is pair-bonds will have a way of showing other potential mates that they are no longer available for reproduction and may even withdraw from potential contact with other suitors to ensure the continuation of their genes. Outside crowded colonies, this is a typical response for many bird species. The other response is typified by the lion pride. A small number of (often related) males will mate with a 'harem' of females who are then given the responsibility of child-rearing and feeding. Thus, when a new lion takes over the pride he will normally kill all the infant lions so that the lionesses are not spending effort on raising another lion's cubs. The same dilemma of 'wasting' valuable resources on another man's genes faces humans, but the response of human social groupings is 'perverse.' Human groups typically consist of a variety of potential male and female mates. In order to ensure a pair-bond humans must again use a symbolic process to pair-bond: they must promise themselves to each other. Thus another human cultural universal becomes ritualised in the myriad forms of marriage ceremony that exist to announce to the community that a pair bond has been established.

So if Deacon can tie the genesis of language down to the end of Australopithecus and the start of homo habilus, what has happened to language since? Whatever language was at the start, it is no longer. We cannot expect our current linguistic abilities to have appeared in total at once. Deacon suggests that a lot of original language was multi-modal, involving body movements, pitch and volume. All of these aspects of communication are still present, but are often ignored by linguists obsessed with predicate logic. We cannot communicate without moving parts of our bodies and Deacon points out that while the 'words' that we concentrate so hard on are being transferred by speech, prosodic features of language are working hard to provide emotional cues. He then describes how the brain probably works in parallel across the two hemispheres to chunk incoming linguistic information so that while one half works on the segmented sounds that constitute lexis and grammar the other tries to unravel the cues provided by prosody. That is, neither hemisphere is exclusively related to language but the two hemispheres simultaneously process different types of linguistic information - and this can be learned by either side of the brain.

This is a superb book. It is almost impossible to do it justice in any length of review. In fact it is 3 superb books - one on linguistics, one on neurology and one on evolution. No make that 4 - it is also fundamentally an anthropological book. While this is its great strength, it is also what makes it a difficult read for most people. Few others could write this book, and most readers will have background knowledge in one or maybe two of these areas. Alongside Deacon's more typical anthropological interests in culture and language (and more than a passing interest in evolutionary theory), his expertise stretches to neurology and experimental biological anthropology. One might call him a renaissance man, but that probably betrays how narrowly-focused many disciplines and specialities have become as much as it celebrates the breadth of Deacon's knowledge.

View all my reviews at Yes, another cut-and-paste from

See more of Terrence Deacon on this blog entry, visit Terrence Deacon's homepage  and access a great article from PNAS outlining his views.

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