All,
Here are some comments on various comments. I succumb, reluctantly, to the
community norm about caps.
[grumble, grumble]
Glen Said ====>
The idea of expansion and contraction is
interesting: rapid expansion of populations
(when selection is relaxed) vs. rapid contraction
of populations (when selection is intensified).
The human population went indeed through a
phase of rapid expansion in the last decades while
natural selection was released through cultural
and technological progress.
Seed Magazine has an article about human
evolution and relaxed selection, too
http://www.seedmagazine.com/news/2008/10/how_we_evolve_1.php <===
Nick Replies ===>
I think this is a confusion between carrying capacity and selection. When, for
some reason, carrying capacity is increased, the whole population can expand,
but this does not stop selection. It may change the nature of selection from
tracking how well individuals can make use of limited resources to how fast
they can reproduce when times are flush, but there is no reason to think that
raising the carrying capacity should "relax" selection.
Russell Wrote ===>
Any extinction event is a collapse of the food web. And selection only
proceeds by means of extinction. So I'm not really quite sure what
you're trying to nuance here.
Nick Replies ===>
OK. Here is where we disagree, I think. Let's worry this a bit, before we
talk about anything else, because it seems absolutely central: When talking
about selection, at what level of organization are we speaking? Gene,
individual, small group, "deme", species, ecosystem? etc. I grew up under the
influence of George Williams who argued that no entity above the individual
could serve as a level of selection and of Richard Dawkins, who argued that no
entity above the level of the gene could serve as a level of selection. So, in
my world, species level selection is not a powerful cause of evolution.
Indeed, on some definitions, species, by definition, cannot compete. Now, in
the last decade, I have thrown off Williams' shackles and started to talk about
selection at the level of the small group. And, indeed, I do know that some
others have started talking about species-level selection. But species level
selection has not become the received view, has it???? If not, the statement
above must be EXTREMELY [whoops, _extremely_] controversial.
Let's pause here and see what others say.
Nick
Nicholas S. Thompson
Emeritus Professor of Psychology and Ethology,
Clark University ([EMAIL PROTECTED])
============================================================
FRIAM Applied Complexity Group listserv
Meets Fridays 9a-11:30 at cafe at St. John's College
lectures, archives, unsubscribe, maps at http://www.friam.org
