Re: Brain size, IQ

Bryant (
29 Aug 1996 21:35:06 -0600

In article <>,
Richard F. Hall <> wrote:
>This is only a bit contriversial in that the cranial capacity is not the
>ultimate gauge of "intelligence".

Of course not; evolutionary theory predicts that the brain is a collection
of task-specific information processing modules, not a general purpose
computer. But, for whatever reason, psychometric intelligence ("IQ")
*does* correlate with brain size, to some extent. It seems to be a
rough, crude gauge, and there are plenty of anecdotal exceptions (but
those don't reduce the statistical significance of the trend).

>>>I am not familiar with Dawkin's hypothesis, but you would be mistaken about
>>>the uncontroversialness of your statement.

What I hoped would be uncontroversial is the notion that brain size was
heritable, at least until relatively recently in hominid evolution. The
evidence for this is the increasing cranial capacity of fossil hominids
as the lineage 'progressed.'

>>What's controversial about the notion that cranial capacity was heritable
>>during human evolution? How else do you explain the dramatic changes in
>>head size through time, as evidenced in the fossil record of our ancestors?
>Cranial capacity is sort of equivalent to RAM memory in your computer. It
>doesn't mean much if your running a 286 with windows 3.0. The idea that
>evolution is creating a "meaner-leaner-brain" is true.

Nice example. This may be relevant to the issue of the evolution of
intelligence, but does not answer my above question: what's controversial
about cranial capacity *itself* being heritable in ancestral popualtions?