From: Damien Broderick (d.broderick@english.unimelb.edu.au)
Date: Sun Apr 22 2001 - 22:51:58 MDT
At 08:58 PM 4/22/01 -0700, Spike wrote:
>That notion about evolutionary pressure towards humans having
>larger heads at birth has the ring of truth to it.
Not necessarily. The evolutionary pressure is presumably psuhing toward
where it's stabilized at (and of course it's cephalization index, ratio of
brain/body, that's the key, not absolute size). I'd guess that what's
happening isn't the result of pressure TOWARD X, so much as relief of
pressure AGAINST X. There's always going to be stochastic variation in all
these physical characteristics (most recently augmented by excellent
nutrition), but in the past many of the outliers died, taking their mothers
with them. That could be construed as evolutionary pressure against
excessive smarts, but it was just a side-consequence of other pleiotropic
factors. Now, using a knife, a clean room, scrubbed staff and a whiff of
anaesthesia, we open the phase space. Praise Caesar!
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.
Damien Broderick
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