Symbolic Species

The Symbolic Species, by Terence Deacon, argues that language and the human brain co-evolved; and that the understanding of symbols is the primary differentiator of human language and human intelligence. The book doesn’t prove either major thesis. But it includes fascinating research and compelling sub-arguments about the nature and evolution of human language along the way.

My favorite section of the book is Deacon’s argument against the Chomskian thesis that the brain is hard-wired for language processing. The book surveys decades of research on language deficiencies caused by brain damage; and recent imaging studies on language processing in healthy brains.

If language was hard-wired, than one would expect that universal features of languages would be implemented in similar regions of the brain. The noun-verb pattern is universal. However, the noun-verb distinction is implemented differently in different languages (some languages use word order; other languages modify the words themselves).

It turns out that the different implementations of grammar utilize different sections of the brain to process nouns and verbs. Therefore, says Deacon, grammar-processing isn’t universally coded in hardware. The brain is designed for language at a different level of abstraction than firmware modules.

Another fascinating section of the book argues that what distinguishes humans from other animals is our ability to understand symbols. Deacon reports a fascinating series of experiments with chimpanzees, showing how chimps have a devilish time doing things we find very easy. Chimpanzees find it nearly impossible to set aside immediate evidence and apply a more abstract understanding.

If you put two piles of candy in front of a child, he will choose the larger pile. But if the larger pile is then given to another child, the first child quickly learns to choose the smaller pile. Chimps never figure this out (although they can learn to choose the number 3 over the number 2). With the pile of candy in front of them, they are overwhelmed by impulse to choose the larger pile.

Deacon tells an interesting “just so story” of the origin of the symbol in human evolution. Humans tend to live in groups, and most often have a pattern of pair-bonding. This is a most unusual combination in the animal world.

In animal species where males contribute to providing for the offspring, there are two basic social patterns. Either the animals pair-bond — in which case the pair lives in isolation — or the animals live in groups, in which case polygyny is the norm. Unless a pair is isolated from the group, or the male has exclusive access to a harem, there is no way for the male to be sure that the young he is providing for carry his genes.

Deacon’s thesis, essentially, is that the wedding ring and the wedding ceremony are the original symbols. Humans invented an abstract symbol and group ritual to mark the fact that a woman is the exclusive sexual property of a man. This allows humans to live co-operatively in groups (which enables more efficient hunting and gathering).

But, to get here, Deacon skips over alternative explanations of the same evidence. The ability to see beyond immediate evidence to consequences remote in time and space can be explained as easily as the foundation of storytelling. Stories have plots — chains of causal relationships that are not visible to the eye. “The saber-toothed tiger over the second hill killed Oog and injured Gah.” And stories turn on character motive — predictions of behavior based on traits and interests. “Chah stayed at the fire and made excellent grain porridge because she does not like to pick eek-berries.” Stories are key to success in hunting, gathering, and transmitting knowledge of tools.

An alternative theory is posed by Robin Dunbar, who argues that gossip was a driving force in the evolution of language. Gossip is language that is used socially, to assess the reliability of social and sexual behavior, and to transmit social norms.

In arguing for the primacy of the symbol, Deacon skips right past other facts he cites. The nerves that go to the frontal cortex travel through limbic areas. This physical fact is a fascinating explanation of art, which combines intellectual stimulation — formal patterns and esthetic properties — with emotional stimulation. Similarly, human decision-making combines reason, pattern-recognition, and gut feeling.

Dunbar is better at marshalling evidence about the unique properties of human language than explaining their cause and origin. Deacon himself argues that language is overdetermined; there are so many advantages that it’s hard to tell what came first. But we’re humans, so we search for causes and tell origin myths, even when we’re using the tools of science.

Also, the bias toward the abstract may influence Deacon’s writing style. Deacon is charmed by the human ability to decode abstractions and process complex sentences; the book could be made easier to read without loss of information, complexity, or meaning, if Deacon weren’t quite so fond of abstraction.

One difficulty for a layperson reading the book is that the book assumes a medical student’s knowledge of brain anatomy. The book uses many terms for brain components, and employs illustrations pointing at brain regions. It would be helpful for the book to include a mapset of the brain and its components, the same way history books often provide a set of reference maps and timelines.

If you’re interested in the topic, read the book. It’s fascinating, though it has flaws and it’s not light reading.