paleoanthropology4: How did humans evolve to acquire language? (v1.0)

 Key reference is prof John Hawks of university of Wisconsin, Madison. 

Language is an extremely important part of human evolution. It is the foundation on which all of society rests. No other species communicates the way we do. It is completely unique. But how did language emerge? One camp sees language itself as the primary target of natural selection. The other camp sees language as a side effect of other kinds of cognitive capabilities driving natural selection. To look at this, we have to look beyond the fossil record. 

Language is a serial communication that follows an order since the person is making a series of sounds. It has to be structured in a very special way so ideas, thoughts and relationships which are fundamentally multimodal can be conveyed serially with sounds. This is done on a dual track One is which sound we emit (phoneme). All languages need a distinctive combination of phonemes. These are accomplished by the vocal cords and the inner ear which came into being through evolution. The second is sounds are grouped into words and sentences. Those are accomplished by the brain. We can’t really know how language came into being from the fossil record, but can study this from examining various animals compared to humans, and the study of human psychology and linguistics gives some pointers.

A species of monkeys in Africa warns each other with sounds when predators are present with different calls for different predators. Chimps can’t emit the right speech sounds due to their vocal cords but have learnt how to sign. One chimp called Washoe born in 1965 at a very young age was taught some signs from the American sign language by Allen Gardner and later Roger Fauts. He learnt more than 300 signs. But there were limits. He could learn the signs and use them in the right context. But he couldn’t put these together into more complicated sentences. The chimp Kanji born in 1980 mastered a few hundred picture symbols (Logograms) that relate to things in his environment. But he was unable to combine them into longer sequences to communicate. So, chimpanzees were unable to create this higher-level structure we call grammar.

Neom Chomsky (born 1928), a famed linguist, who is often called the father of modern linguistics, said that there are patterns in language you can’t learn just by listening to what other people say - it can't be just learnt. The input received by young children is in itself insufficient to explain their detailed knowledge of their first language. Therefore, there is something innate that human minds have that gives us that higher grammatical ability. He called this argument the poverty of the stimulus. How did this ability occur through natural selection? Chomsky said that language could not have evolved as a natural selection focus, but this ability can only be explained as the side effect of other kinds of cognitive functions that were the driver of natural selection.

Stephen Jay Gould (born 1941) a noted evolutionary biologist also furthered this same argument. He had a collaboration with a geneticist Richard Lewontin (born 1929) that gave a way of talking about the adaptation of things as a side effect of other types of evolutionary constraints. Their example was based on St Mark’s Cathedral in Venice. There are a series of domes, and these are supported by arches in between. The region between the arches and the dome are triangular shaped spandrels. They are an architectural necessity because without them the dome cannot be supported. But spandrels have elaborate paintings and visitors talk about spandrels in terms of the story they tell. But that was not the real function of the spandrels. Another example is snails have a curved shell, but there is a space between the curves. The space is there only because the shell is curved – that is the only reason. But some species keep their eggs there and they are called brood spaces. We might imagine that was the purpose for the space, but it is not.  

This viewpoint met heavy opposition – a notable example is Stephen Pinker (born 1954) who felt language is basically innate. Kids start learning the phonemes as early as 6 months old and start learning words as early as one year starting with a few words like mama. When they are 3 years old, they begin to string words together. Between 3 and 5 they make characteristic mistakes (like try always to add ‘ed’ to make a past tense) and that gets fixed and more contextual later in development. Pinker though language was complex and therefore did not believe it was just a side effect but was innate. He felt natural selection made it a focus to learn language. He answered the stimulus of poverty argument by saying that learning a language requires a large number of steps and complexity is mastered a little at a time. Natural selection would favor those genes that make it ordinary to get to that complexity stepwise. This approach is called the Baldwin effect.

Many linguists today disagree to some extent with both Chomsky and Pinker. They believe language is largely shared and learned and does not take a lot of innateness. They believe language is learnt uniquely and differently by each person. The Broca’s area of the brain is responsible for speech. When that part has issues, it is shown that the function migrated to a different part of the brain. There is plasticity. Michael Tomasello (born 1950) is a modern psychologist and linguist who also has this view. He has demonstrated that learning occurs best when the child and the caregiver focus their attention on the same object, which clearly is the case for learning words in humans. That is fundamental to learning language in humans. It seems to be a unique human trait. Chimps do this very poorly. 

To get back to the original debate – is language the target of natural selection or a side effect - there is a range of answers today and there really is disagreement on how much natural selection was involved in the acquisition of language. It is an area of active debate.