While obstetrics might be one factor that helps, I think one should not
discount the better nutrition and more stimulating environment that has
developed. If it was just an issue of birth skull size we would see
national differences much more clearly than is currently observed in the
Flynn effect due to differences in health care. Evolutionary pressures
are too slow to act much over the ~4 generations ibstetrics has become
good.
If Friedmans idea is right, then we would see an increase in bright
people that would otherwise not have been born (or made stupid by brain
trauma), so his model predicts increased variance and a very slight
increase in mean, not that the mean and median are climbing.
On Mon, Apr 23, 2001 at 02:51:58PM +1000, Damien Broderick wrote:
>
> I like Friedman's idea that there should be selection pressure toward what
> amounts to Coneheads. I don't buy his neural reasoning against this. But
> note: if hypertrophied intelligence is a side-effect of extra large
> cortical area (all things being equal), it must have had no overwhelming
> advantage in our classic evolutionary environment; today it has only a
> *neutral* impact, or worse, if it really does conduce to smaller `selfish'
> family size.
The brain is metabolically very expensive, if you have trouble feeding
yourself a larger brain might not be an advantage at all.
Apropos smaller families, this could also be a factor: I remember seeing
in one of my psychology textborns that firstborns often exhibit higher
IQs than their siblings. The reason for this is unclear, possibly
because they are surrounded by a higher mean IQ.
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