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From: g-rh@cca.UUCP
Newsgroups: sci.bio
Subject: Re: Animal hybridization: gulls
Message-ID: <14414@cca.CCA.COM>
Date: Sat, 28-Mar-87 09:30:48 EST
Article-I.D.: cca.14414
Posted: Sat Mar 28 09:30:48 1987
Date-Received: Sun, 29-Mar-87 23:39:34 EST
References: <7817@utzoo.UUCP>
Reply-To: g-rh@CCA.UUCP (Richard Harter)
Organization: Computer Corp. of America, Cambridge, MA
Lines: 59

Richard Snell writes an excellent article on the gull cline.  It is
always a pleasure to read material from people who have the facts and
the current data at hand.  He asks for sources for the article
I wrote, particularly with reference to interbreeding of intermediates
in the claimed cline and the stated size difference between the 
British lesser black-backed gull and the British herring gull.
Fair enough.

First of all, the purported size difference was a misreading on my 
part, for which my apologies.  Mea culpa, and all that.

The source was "After Man, a Zoology of the Future", by Dougal Dixon
St. Martins press, 1981.  The dust jacket description of the author
reads:

	"Dougal Dixon studied geology and paleontology at the 
	University of St. Andrews, where he continued as a 
	research student to revise the standard work on the
	paleontology of the British Isles.  In recent years he
	has worked in publishing and has contributed numerous
	articles about earth science and evolution to encyclopedias
	and popular science books.  Model making and the creation
	of animated films occupy much of his spare time..."

The book is a fun book -- it is a speculation about the course of
evolution in the next fifty million years with the fundamental
assumption that homo sapiens goes extinct in the near future.
The book definitely is not a scholarly work, but it is a great
pleasure to read, and I can recommend it.  Although the book is
not a scholarly work, it does draw upon and explains a multitude
of concepts in Zoology, Ecology, and Evolutionary theory.  The
prolog contains a summary of major concepts in these fields.
Among them is a description of what a cline is, and the example
I gave, with no more detail than I gave.

It is disappointing to learn that the example is not solid.
At least that is what Richard is saying and it seems clear that
he has detailed professional knowledge at hand, so I expect that
he is right.

My guess is that the cited example was a standard example of a
cline a number of years ago, and that the author simply used a
textbook example, which, in the light of detailed examination
turned out to be much less clear cut than was assumed.  The book
does give a bibliography and a list of sources of reference
but there are no specific citations.  [In checking the bibliography
I note the presence of the notorious Hoyle "Lifecloud" article
and Dawkin's "The Selfish Gene", which does not give me warm
fuzzy feelings of confidence in the reliability of his sources.]

There is a moral here: when you give information, include your
sources.  There is a tendency on my part, and I suppose on many
people's part, to read something and remember the assertion without
remembering where it came from.  The result is that one ends up
"knowing" a lot of things as isolated "facts" without knowing
where they came from or how good they are.
-- 

Richard Harter, SMDS Inc. [Disclaimers not permitted by company policy.]