[LEPS-L:8045] Re: Extinct 'species'

Michael Gochfeld gochfeld at eohsi.rutgers.edu
Thu Nov 30 07:52:50 EST 2000

> Doug concluded:  so the lack of new records is not necessarily convincing evidence of extinction. PROVING that anything, even a large vertebrate, is extinct is (as those in Tasmania can attest) nearly impossible.

This reminded me of Popper's black swan idea (I don't know whether it is a theorem or a law or what), namely, that no matter how many white swans you count, you can never prove that "all swans are white", but you only need to find one non-white swan to disprove that statement.

That's why in science we don't try to "prove" our hypothesis, rather we pose null hypotheses which we try to reject, recognizing that if we reject the null hypothesis it provides support for, but does not prove our underlying or alternative hypothesis.

So we CAN'T prove that something is extinct, but we can gain confidence from repeated negative surveys that it is NOT LIKELY TO EXIST (I suppose).

For example, The USFWS has tried periodically to mount evidence for declaring that the Ivory-billed Woodpecker is extinct, so it can be removed from the endangered list. But since there have been few (or no, depending on your degree of skepticism) confirmed sightings in recent decades, people don't bother to look for it in places where it used to occur.

So it's heartening to know that the borer has been re-discovered.  In NJ the Arogos Skipper has been rediscovered after 20 years, but prior to that we hedged its status as "probably extirpated", although in retrospect, it was a species that had been unrecorded for many years and so may actually be an erratic colonist.

M. Gochfeld


   For subscription and related information about LEPS-L visit:


More information about the Leps-l mailing list