A Thought about the evolution of the brain

You read every once and a while that the human brain has not changed in 200,000 years. (Here is an example.) Marvin Minsky in his recent book describes the brain as composed of a number of "resources". He writes:

every brain has hundreds of parts, each of which evolved to do certain particular kinds of jobs; some of them recognize situations, others tell muscles to execute actions, others formulate goals and plans, and yet others accumulate and use enormous bodies of knowledge. And though we don’t yet know much about how each of those hundreds of brain-centers works, we do know that their construction is based on information that is contained in tens of thousands of inherited genes—so that each brain-parts works in a way that depends on a somewhat different set of laws.

We also know, however, that brain organization is flexible. Thus we know that a musician's brain shows different patterns of activity when that person hears music than does a non-musician's brain exposed to the same music. We know that after a stroke or other injury to the brain a person can relearn things that have been lost to the injury -- that other parts of the brain will take over some of the functions previously carried out by the injured sections.

The genetic coding for the brain seems to result in the same function being carried out in about the same location in the brains of different people. However, experience and training can effect how much of the brain is allocated to each of the functions.

Think then about a modern American who has perhaps attended school for 14 years on average and read a great many books and magazines. That person has listened to many thousands of hours of music, and watched many thousands of hours of movies and television. Would the allocations of functions to parts of the brain be the same as those of a human say 150.000 years ago. At a gross level perhaps, but I would guess that more of the modern brain would be devoted to language, that the links between visual centers and language centers would be far more developed, and that more of the brain would be devoted to the interpretation of two dimensional moving images than would be the case of a paleo-human hunter gatherer.

It seems to me that culture would influence the allocation of functions within the brain, and that tens of thousands of years of evolution of culture would in fact change the brain.

Minsky suggests further:

Each of our major “emotional states” results from turning certain resources on while turning certain others off—and thus changing some ways that our brains behave.

If the functioning of the brain is based on patterns of activation over the hundreds of different parts, and culture influences the size of the regions of the brain allocated to different parts, so too culture might be assumed to modify the pattern of activity across those parts.

If you think about it, computer software works by influencing the physical properties of computer hardware. Storing a one or a zero is done by changing the state of a memory unit. The change in a computer's behavior with a change in software (say from an Internet browser to a word processor) is simply the result of a change in its physical state.

So too the changes in the behavior of the brain seem likely to be the result of changes in the physical properties of the brain -- such as changes in synaptic strength. It seems likely that the state of the modern American brain is different from the state of the paleo-human hunter gatherer brain not so much due to evolutionary changes as to changes in experience that are the result of millennia of cultural development, a process that is much more rapid than evolutionary changes.

I would now guess, which I would not have done a generation ago, that the changes in structure may be so macro as to be observable were we to have a paleo-human hunter gatherer for comparison.