The Cambrian Explosion

["Terry Colvin" <colvint@CC.IMS.DISA.MIL>]

Forwarded message, 3/7/1995 11:04 AM

This is a paraphrase of what S. J. Gould said last year when he spoke at the 
Univeristy of Wisconsin on contingency and evolution:

Species die for many reasons and sometimes those individuals that one would 
predict to "survive" do not. Darwin's law of natural selection can sometimes 
be phrased "Survival of the luckiest" for this very reason.

For example, think of small, isolated pond which has existed for millions of 
yers. Within this pond, fish have been evolving. One species has recently 
become the best Dawrinian anywhere: it is the fastest, smartest, strongest 
fish species in the world. 99 of every 100 egg hatches and survives to 
adulthood. 98 of those adults breed every where. Clearly, this is a 
successful fish species. However, one day, by a stroke of bad luck, the pond 
completely dries up, the environment changes too greatly for even the most 
Darwinian fit fish ever. It becomes extinct. 

This is probably what happened to many of the species in the Cambrian...they 
were greatly evolved for certain situations and survived, but when the 
selective pressure changed, they disappeared forever. This is what we see in 
our own flora and fauna, so no one should be too surprised.

For more, see his book A WONDERFUL LIFE


Thom Quinn
Univeristy of Wisconsin