Darwin-L Message Log 6:92 (February 1994)

Academic Discussion on the History and Theory of the Historical Sciences

This is one message from the Archives of Darwin-L (1993–1997), a professional discussion group on the history and theory of the historical sciences.

Note: Additional publications on evolution and the historical sciences by the Darwin-L list owner are available on SSRN.

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<6:92>From HOLSINGE@UCONNVM.BITNET  Wed Feb 23 07:12:33 1994

Date: Wed, 23 Feb 1994 07:56:12 -0500 (EST)
From: "Kent E. Holsinger" <HOLSINGE%UCONNVM.BITNET@KU9000.CC.UKANS.EDU>
Subject: Re: Reconstructing backwards
To: darwin-l@ukanaix.cc.ukans.edu

Jeffrey Wills raises an interesting question:

> I assume that biologists have more confidence in their ability to describe
> initial, primordial, primitive, vel sim. life and probably approximate (even
> if rough) story line starting from simple cells on up.  Question: does
> knowledge about the root make a difference in method in reconstructing the
> tree?

The answer:  Yes or no, depending on who you talk to.  Some cladists have
argued that the *only* information fossils provide is additional information
on the pattern of character state distributions.  The fact that a particular
fossil is 45 million years old provides no additional information about the
sequence of evolutionary events.  In fact, they would go so far as to argue
that we should not make *any* assumptions about the evolutionary process,
deducing our hypothesis of relationships *only* from the pattern of shared
characteristics.

Evolutionary systematists a la Mayr and Simpson, on the other hand, make
extensive use of evolutionary scenarios in the process of building
phylogenetic trees.  My impression (I'll be interested to see if other
biologists share it) is that the tendency is to exclude hypotheses about
the underlying evolutionary process while building trees, except where we
have *independent* reasons for modeling that process in a particular way (e.g.,
molecular sequence data).  The reason, at least in part, is that we expect to
use these trees in *tests* of evolutionary scenarios and hypotheses about the
evolutionary process.  If we have included a particular scenario as part of
our justification for choosing one tree as the best representation of history,
it becomes (almost, not quite) circular to test our hypothesis using that
tree.

-- Kent

+--------------------------------------------------------------------+
|  Kent E. Holsinger            Internet: Holsinge@UConnVM.UConn.edu |
|  Dept. of Ecology &           BITNET:   Holsinge@UConnVM           |
|    Evolutionary Biology, U-43                                      |
|  University of Connecticut                                         |
|  Storrs, CT   06269-3043                                           |
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