Each species will balanced the use of resources between activities such as feeding, breeding, avoiding predators, and learning how to optimise these resources by using the brain. There are many different evolutionary strategies. For instance some fish lay millions of eggs while humans have small numbers of young and use their brain to maximise the survival of each youngster. However we can be certain that no animal evolves an organ bigger than it needs, and if conditions change an organ will shrink if it is bigger than necessary. This will apply to every organ and function and no species will not evolve a brain bigger than it needs.
A particular feature of the brain is that it has to learn about its environment, usually by trial and error experimentation. This takes time and everything that has been learnt is normally lost when the “Host” animal dies. The brain will therefore be limited in size by the amount that could be learnt, especially in the earlier stages of life. In effect there is a ceiling at what can be learnt by trial and error learning and hence a limit on the “intelligence” of the species. Humans appear to be the only species which has broken through this barrier and it is instructive to examine this in terms of the economics of the learning/teaching relationship between infant and adult.
The breakthrough almost certainly relates to tool making in the widest sense – not only including physical tools but also communal skills such as hunting and communication tools such as language. There is no evolutionary advantage in an individual discovering a new tool unless the ability to exploit the tool is passed on from generation. However if some way can be found to ensure the skill is passed on this increases the species changes of survival and hence moves the optimum balance between feeding, breeding, avoiding predators and brain size towards a larger brain. But such improvements are probably limited as long as learning is still dominated by trial and error.
It is worth looking at how a chimpanzee “trains” its youngster to open hard nuts. [The Brains of the Great Apes] Stones are rare on the floor of the forest but the mother has two stones. The nut to be broken is placed on the anvil stone and the nut is then hit hard with the hammer stone. This is done in front of the youngster who has the opportunity to try it out for himself on a trial and error basis. OK as far as it goes but there are some easy ways it could be improved which suggest how we may have evolved. For instance the adult could speed learning by directing the youngster to take action – with actions such as placing a nut in the hand and moving the hand to the anvil. This could speed up teaching and allow more complex tools to be taught. Teaching in this way, and the ability to teach more complex tools could result in enlargement of the parts of the brain related to use of the hands as suggested by Rapid Evolution of the Cerebellum in Humans and Other Great Apes.
Teaching would become more effective if words were given to the “nut” the “anvil” and the “hammer” and the act of using the hammer. Words for “good” and “bad” would also be useful. It would also help teach in the search for new hammer and anvil stones as the mother could take the infant to a place where suitable stones are to be found and indicate which are suitable for which purpose.
So let us assume that an early hominid developed better teaching techniques which reduce the time needed to teach its children to learn the tool making culture by , say, three months. Evolution could then proceed by reducing infancy and increasing breeding time or the length of infancy could remain the same and new cultural tools developed which improve survival at the old breeding rate. (The current world population explosion has occurred because we have introduced tools which greatly increase survival at something like the old live birth rate!)
Once a primitive language has been established there are four ways in which better teaching of the tool-making culture can boost survival rates:
- · Teaching about dangerous situations: If a culture involves hunting large and potentially dangerous animals it could be dangerous to take the young to learn by watching the hunt. However if the hunt techniques, and the dangers, can first be taught by means of language the young will be far less likely to be killed or injured because they knew what to expect.
- · Speed learning: An animal brain needs two learning mechanisms. The most primitive is that if “A” and “B” occur together an “B” is dangerous take avoidance action whenever “A” occurs – because it is too risky to experiment to find out if “A” and “B” are causally related by trial and error. The second mechanism if simply to recognise the pattern “A” and “B” and use trial and error learning to establish whether there is a causal relationship. This is clearly a slower process – but is a more reliable way of finding out what to expect if either “A” or “B” occurs. If a social group has a reliable culture and uses language as a teaching tool, learning is far faster if the infant accepts anything it is told by using the first mechanism. However the “check” on reliability associated with trial and error learning is bypassed. Once a more advanced society has developed this speed learning mechanism makes it far easier for influential individuals to disseminate information which may not be based on reliable evidence.
- · Generalization: If you can introduce a high level category, such as “mammal”, there is no longer any need to learn for the bottom up, that each individual mammal species has hair, has live young, and feeds it young on milk. Not only does this allow faster learning – but it almost certainly requires less neurons to hold the information. Faster learning means more learning is possible, and using the brain as a more efficient knowledge store means that more can be learnt without any increase in brain size.
- · Rule-based learning: The work I have already outlined elsewhere on this blog suggests that bthe brain uses a pattern based internal language. Complex tools are best handled with a rule-based system and the research done with CODIL shows how a pattern based system can morph into a rule based system when necessary. This provides a framework where the initial primitive language can acquire a series of syntax rules to help convey more advanced ideas.
All these factors combined together to suggest that our intelligence and our use of natural language arose because we crossed over an important tipping point. Better language means faster and more effective learning about tools while at the same time using less of the brain’s resources. This allows the “invention” of even better tools – and language is a tool which can be improved using the more powerful tools. The more language improves from generation to generation the greater the benefits become.
What this all means is that once the use of language becomes an important factor in survival of a species there with be an avalanche effect where the language takes off like a rocket, taking with it all the things a language allows you to do better. No significant change in the biological brain is needed to fuel this explosion – and in fact the advances in cultural sophistication will be so rapid that slow but steady genetic evolution would not be able to keep up with it.
It would seem that the main reason humans are different to other animals is that we happened to be the first animal to reach the tipping point where the more your know the easier it becomes to learn even more. Neanderthals probably had a very similar brain to ours, and while they may not have had enough language to pass the tipping point on their own they could almost certainly have been capable of learning natural language from Homo sapiens!