Re: Extinction

[Stanley Friesen <sarima@friesen.net>]

At 12:41 PM 3/24/00 -0500, Dinogeorge@aol.com wrote:

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

That is debatable.  It will have >global< causes, certainly, since a 
confluence of local causes is very unlikely to produce a global 
effect.  But it is *not* strictly necessary for there to be one 
cause.  Certainly one of the causes will be "final", in the sense of being 
the last one - the one during which the maximum extinction occurs.  But it 
is entirely possible for that cause to be insufficient in itself to cause 
the full series of extinctions. That is, if such a final cause had occurred 
in the *absence* of the other causative factors it would NOT have caused a 
mass extinction.

I maintain that in that situation, where none of the contributing factors 
is sufficient *by* *itself* to cause a mass extinction, then it is 
sophistry to claim there is only one cause.  It oversimplifies such a 
situation to claim that the final cause is the sole cause merely because it 
is final.

>  One such single cause can be asteroid impact. The problem
> with multiple causation is to get all the causes to coincide in their
> effects;

They do not need to, for extinctions all that is necessary is for them to 
have mutually amplifying effects, or even merely additive.

>  ... The asteroid impact at the K-T boundary was
> gigantic, with devastating worldwide physical effects whose traces have been
> well documented in the geological record. If you say that this event and the
> K-T mass extinction had nothing to do with one another and are purely
> coincidental,

Who, here, is saying that!!!  I have heard nobody say any such thing.

--------------
May the peace of God be with you.         sarima@ix.netcom.com