Re: Extinction

[Joseph Daniel <jdaniel@aristotle.net>]

Dinogeorge@aol.com wrote:

> Not exactly right. A mass extinction will have a >single< global cause, not
> >multiple< causes.

Wouldn't it be nice if nature really worked in such a black and white, clearcut
manner? Unfortunately, as any ecologist that is not bald faced lying to you will
say, the answer to any ecological question can usually only be honestly 
expressed
as, "it depends..." If you try to point to a single cause for an ecological 
event
you are almost assuredly wrong.
Take this asteroid theory for instance. I don't think anyone would say that it
didn't hit. But, in the span of 600 million years of life on earth, odds are 
that
a major extinction could easily happen in conjunction with and completely
unconnected with a major impact. Am I saying this is what happened? No. But it 
is
not enough to show time linkage, one also has to show cause and effect. Other
major impacts have occured without huge mass extinctions and mass extinctions 
are
thought to have occured without major impacts. Therefore, it seems the most
parsimonious answer is that other factors contributed to the demise. The 
asteroid
could have been a major player and probably was, but it would be likely 
incorrect
to say it was the ONLY factor. To say this requires extensive data we just don't
have. Show me a paleontologist or ecologist that says this is the only right
answer without question and I will show you a paleontologist or ecologist that
doesn't have all the facts.

Joe Daniel