Gould's theme is that natural diversity is usually attributable to nothing
more interesting than a drunkard's walk away from a wall. Life starts
simple (against the `left wall') because it can't start any other way.
Mostly it stays simple, by mensurable metrics. Even now, arguably, most of
the earth's biomass is simple bacteria. Over time, some variants wander off
to the right. Humans and other large critters exist off on the right-most
tail of the curve, but not because there is any `complexification drive'.
The test of this anti-progressivist thesis is, e.g., whether ancestors are
simpler or more complex (by some measure) than descendants. Dan McShea's
landmark studies show a random balance of the two directions. (McShea was
at Michigan, is now at the Santa Fe Institute.) He finds that diversity is
better explained by `passive' than by `driven' trends. The argument seems
solid.
I wonder what the other Santa Fe folks make of this. Stuart Kauffman urged
Roger Lewin to talk to McShea when Lewin was writing his (excellent)1993 pop
sci book COMPLEXITY. Dawkins, at the other extreme, also insists that
there's no tendency in evolution toward greater complexity, merely toward
successful adaptation to fortuitously changing conditions. Since the Red
Queen's race argument insists that some of those environmental conditions
include other contestants, I'd have expected a driven complexifying trend to
show up. Not so, insists Gould and his sources.
Incidentally, for baseball fans (Australians like me haven't got a clue),
his argument for why 0.400 batting has vanished due to general *improvement*
of the game (closing up of variance) is beautiful and compelling. This must
surely map in part on to the observed difference between males and females
on aptitude tests - I wonder if it means that general excellence in females
permits less opportunity for extreme outliers, so the `absence of women
geniuses' is an artefact of the metric? (Probably not, since both sexes are
tested by the same instrument and their scores can be compared directly.
Still, it might have some bearing on the issue...)
Anyone else read this Gould book yet?
Damien Broderick