Wednesday, 18 June 2014

When did language Evolve

Adam Benton recently posted "When did Language evolve" on his blog Evoanth which looks at the latest information about the evolution of the hyoid bone, which is linked to the tongue and other muscles which are involved in speech.

Clearly there is a relationship between our ability to vocalise and our use of language - but a key question is what came first.  Did early humans use imitation animal calls to help in hunting and then use a feature that already existed to communicate - or did our vocal tract evolve because we were already using a simple language and a clearer voice make things better. If we think of it in terms of information flow one thing seems obvious - our ability to makes a wide range of sounds, with clicks, whistles and a wide frequency range is far more than is needed to support our natural language. In the animal kingdom a number of birds, such as the Myna bird,are very good at imitating the sounds it hears - and also has the Fox2 gene supposed to be responsible.

However my own feeling is that natural language is almost entirely due to cultural evolution and I posted the following comment to Adam's post.

There is a real danger of confusing biological evolution with cultural evolution, and we all know, because we see the changes in our own life time, that language is a tool which dynamically changes from generation to generation. It seems possible that the time frames of biological and language evolution are so different that there have been few, if any, significant biological changes in the brain, or in organs such as the hyoid bone, since natural language started to evolve.
In biological evolution all organs in a given species are competing for resources and no organ, including the brain, will grow bigger than it needs to. There is no point in having a bigger brain if the host animal’s life time is too short to fill it with information useful to survival. Different species handle this in different ways – and humans have gone for the somewhat risky option of a very small number of infants, a long infancy with heavy parental involvement, and a very high percentage of infants surviving to adulthood – a tactic which allows a larger, and more “knowledgeable” brain to be supported. This is really only viable if there is a significant amount of cultural information to pass between generations – and early tool-making (in the widest sense to include specialised food-gathering techniques) could well have been the trigger to humans having bigger brains, and longer infancies, than their great ape relations. This process resulted in a slow but steady increase in brain size and cultural complexity over the last few million years – but initially possibly no more than a simple proto-language involving the ability to give names to objects.
The critical factor turns out to be the efficiency of learning – which in the great apes – and undoubtedly early humans – depends on trial and error imitation using visual signals. This process is time consuming and almost certainly limits the complexity of tools which can be easily learnt by copying. The obstacle to be overcome is the transfer of cultural knowledge held in a neural network (a parallel processing device) in the adult brain to a similar network in the infant brain, via sequentially operating sense organs. Language provides a way of bridging this obstacle.
I am currently working on a symbolic language model to understand how an animal brain could store and process patterns and asking what evolutionary changes would be required to produce a human brain. It seems that apart from changes in capacity the only significant changes relate to learning efficiency. Once a certain threshold of language ability is reached the effect would be a very rapid expansion in language capability, accompanied by an increase in tool-making ability.
The critical point seems to come when the quality of cultural information to be transferred using a primitive proto-language is more reliable than anything that can be learnt by simple trial and error learning. At this point it pays for the infant to “fast track” learn information transferred verbally and there is a possible minor biological evolutionary change that could encourage children to short cut the brain’s normal learning mechanisms if information comes from an “informed adult”. The ability to name simple abstract objects allows children to be taught without experiencing. (An “elephant” is a “Big” “grey” “quadruped” with “long nose” so a child does not have to see one to recognise one.) It also becomes easier to teach tool making which involves longer sequences of operations. Because language is a tool, better tool-making abilities means better language generation after generation, and the process would have taken off like a rocket, compared with usual evolutionary time-scales.
There is an important side effect. Efficient language learning actually means that the brain needs fewer neurons to store a given amount of information – so that the more language develops the more knowledge the brain can hold – so there is no longer any pressure for the brain to get bigger! In fact this increase in learning efficiency may mean that our brains are now bigger than we need to survive in purely biological evolutionary terms. This could be the reason why we have the “spare capacity” to enjoy Beethoven’s music or Shakespeare’s plays – or carry out research into the evolution of language!
If my approach proves valid it suggests:
• What we call Natural Language is 99.99% cultural
• Language may have really got underway in one small group of humans and expanded very rapidly. Once one group acquired it there would be no problem in the cultural skills passing to other groups and possibly even to other Homo sub-species.
• Tool making skills would have started to improve alongside the growth of language skills. This would suggest that natural language started in the last 100,000 years or so.
• There is no need to assume any significant biological change between humans before and after the advent of language. (This suggests that the development of the hyoid bone pre-dated the development of any form of advanced language.)
• The model also suggests that some of our human failings – such as confirmation bias – arise because our brain works in basically the same way as animals – but we have stretched some of the innate limitations almost to breaking point.

No comments:

Post a Comment