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Re: Extinction

From: John Bois <jbois@umd5.umd.edu>

 > Where am I going wrong?  Using your "data" I made 72 little slips of 
 > paper and colored 30 green (mammals), 12 red (dinos), 5 pinks, 15 blues, 
 > 10 yellows.  Then I took out 30%--and your 75% extinction rate is  
 > high.  In Ward's Nov. _Science_ paper 70% is cited so I used that--or 22 
 > slips at random.  I simulated 10 K/T extinctions.  Only one <clade> became 
 > extinct (Yellow) and that only happened once!!!

If I remember right, the _Science_ paper had a 70% *extinction* rate,
not a 70% survival rate.   Certainly a 30% species extinction rate
is way low, as the *family* extinction rate is almost that high, and
rates get larger, not smaller, at lower taxonomic levels.

I think this is your problem.  At a 30% species extinction rate, few
higher taxa will become extinct, as you found out.

Another way to get the species extinction rate is to *average* the
extinction rates from the various non-protected groups in Archibald's
data.  I am fairly certain that this number will come out to be over
50% at the very least.

swf@elsegundoca.ncr.com         sarima@ix.netcom.com

The peace of God be with you.