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From: werner@aecom.YU.EDU (Craig Werner)
Newsgroups: sci.bio
Subject: Re: Why are Humans as Smart as They Are?
Message-ID: <1253@aecom.YU.EDU>
Date: Tue, 4-Aug-87 21:47:16 EDT
Article-I.D.: aecom.1253
Posted: Tue Aug  4 21:47:16 1987
Date-Received: Sat, 8-Aug-87 07:11:28 EDT
References: <1041@ttidca.TTI.COM>
Organization: Albert Einstein Coll. of Med., NY
Lines: 44

In article <1041@ttidca.TTI.COM>, jackson@ttidca.TTI.COM (Dick Jackson) writes:
> 
>                                                It seems to me that we
> are much too mentally able than we need to be.  What was the environmental
> pressure that made us THIS smart?  


	This is a question whose answers are bound to be unsatisfying.

	However, the phrasing reveals a common misconception of evolution,
that it in fact has a reason for everything.  The pressures of evolution
are mostly negative.  Unfavorable traits are weeded out, even if their
status as "unfavorable" are only relative to a changing environment, or
"superior" competitors.  There is very little positive selection.

	An answer closer to the original spirit of the question would
go as follows:  the various parts of the brain utilize very similar
mechanisms of synaptic transmission and selection in the visual cortex
and speech centers (clearly advantageous) probably brought other areas
(whose growth was only selected against by the fact that the total
cranial size had to be, on the average, smaller than a female pelvis).

	There is a far more compelling reason.  It is now generally
forgotten that diseases such as Measles, Smallpox, Rubella, Mumps,
Cytomegalovirus, Herpes, etc., can and do infect the brain with
neuronal destruction, generally during childhood.  Since selection
only occurs on the reproductive population, that means that selection
of brain size generally occurred on a population whose neuronal complement
had been ravaged by disease.  Disease, I might add, that generally does
not exist in the developed world today.  This would then give the
appearance of "redundant" neurons, which are available for higher
functions, in the absence of such disease.

	Then, there is just the matter of projection.  Most of the
acheivements of mankind that are remembered are performed by the
top few percent of talented persons in that respective area.  The
unconscious extrapolation generalizing back can account for most of the
bewilderment.

-- 
	        Craig Werner   (future MD/PhD, 3 years down, 4 to go)
	     werner@aecom.YU.EDU -- Albert Einstein College of Medicine
              (1935-14E Eastchester Rd., Bronx NY 10461, 212-931-2517)
                                "Meiguanxi ye meibanfa"