On Tue, 2 Sep 2008 10:17:31 -0700 (PDT), LarryG
wrote:

For the past week or so, I have been reading "The Cycle of Cosmic
Catastrophes: How a Stone-Age Comet Changed the Course of World
Culture" - by Richard Firestone, Allen West, Simon Warwick-Smith. The
authors attribute the extinction of the wooly mammoth, and other north
american megafauna, and the paleo-american Clovis culture, to a
probable comet strike at what is now Lake Michigan...

The science is generally poor. A few people claim to have found evidence
of a Holocene impact, but this is weak and not well supported. Most of
the events the authors attribute to external influences have simpler and
more widely accepted possible causes. Their approach reminds me a lot of
Velikovsky: start with the assumption of an event, and then try to make
history (and prehistory) match it- even if the fit is often poor.

That said, it is obvious that we are vulnerable to the effects of
supernovas, comets, and any number of other extraterrestrial events.
What we don't really understand yet is the actual frequency of these.
They have probably had significant influence on the path life has taken,
but most likely not on the immediate evolution of humans.
_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com