The Mind Made Flesh: Frontiers of Psychology and Evolution by Nicholas Humphrey

The Mind Made Flesh: Frontiers of Psychology and Evolution by Nicholas Humphrey

Author:Nicholas Humphrey [Humphrey, Nicholas]
Language: eng
Format: epub
Published: 2012-08-28T00:00:00+00:00


Let this be as it may. You do not need to be convinced by every detail of the story to accept we are on to an interesting set of possibilities here. Let's ask what else falls into place if it is right.

An obvious question is: if there have been these steps backwards in the design of minds and bodies in the course of human evolution, just how could they have been brought about genetically? For, in principle, there would seem to be two very different ways by which a genetically controlled feature, such as hair or memory, could be got rid of, if and when it was no longer wanted: it could be removed, or it could be switched off.

It might seem at first that removal would be bound to be the easier and more efficient option. But this is likely to be wrong. For the fact is that in order to remove an existing feature, as it appears in the adult organism, it would often be necessary to tamper with the genetic instructions for the early stages of development, and this might have unpredictable side effects elsewhere in the system. So in many cases the safer and easier course would actually be to switch the feature off-perhaps by leaving the original instructions intact and simply inserting a `stop code' preventing these being followed through at the final stage .28

The most dramatic evidence for switching off rather than removal of genetic programs is the occurrence of so-called `atavisms'-when ghosts of a long-past stage of evolution reemerge as it were from the dead. To give just one remarkable example: in 1919, a humpback whale was caught off the coast of Vancouver which at the back of its body had what were unmistakably two hind legs. The explanation has to be that, when the hind legs of the whale's ancestors were no longer adaptive, natural selection eliminated them by turning off f hind-leg formation, while the program for hind legs nonetheless remained latent in the whale's DNA-ready to be reactivated by some new mutation that undid the turning off.

Do such atavisms occur in the areas of human biology we are interested in?

Let's consider first the case of hair. If body hair has been turned off, does it ever happen that it gets turned on again? The answer is most probably: Yes. Every so often people do in fact grow to have hair covering their whole bodies, including their faces. The best-documented cases have occurred in Mexico, where a mutant gene for hairiness (or, as I am suggesting, the return to hairiness) has become well established in certain localities. 2'

But how about the case of picture memory? We have seen two remarkable cases where the capacity for perfect recall popped up, as it were, from nowhere: the mnemonist S. and the idiot savant artist Nadia. But lesser examples of much better-than-average memory do turn up regularly, if rarely, in a variety of other situations. The capacity for picture memory is actually not uncommon in young children, although it seldom lasts beyond the age of five years.



Download



Copyright Disclaimer:
This site does not store any files on its server. We only index and link to content provided by other sites. Please contact the content providers to delete copyright contents if any and email us, we'll remove relevant links or contents immediately.