Darwin-L Message Log 5:80 (January 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.

<5:80>From HOLSINGE@UCONNVM.BITNET  Fri Jan 14 19:25:28 1994

Date: Fri, 14 Jan 1994 08:09:07 -0500 (EST)
Subject: Re: Systematics and linguistics
To: darwin-l@ukanaix.cc.ukans.edu

Sally Thomason suggests that one difference between linguistic evolution and
biological evolution is the "decay and ultimate disappearance of systematic
correspondences."  Actually, the same thing happens in biology.  If biologists
limit themselves to an analysis of morphological features, for example, it is
often difficult to determine which structures are homologous with one another.
Consider the difficulty of comparing a mammal, an insect, a sponge, a
liverwort, and a flowering plant based only on morphological features.  It
would be very difficult to construct a tree representing their relationships
correctly without the use of ultrastructural data or molecular sequence data.
The morphologies are so different that they are no longer even comparable.

Even with molecular sequence data there is "decay and ultimate disappearance
of systematic correspondences."  After all, there are only four bases in DNA
and if the number of mutational events that separate two lineages increases
the longer they are separated from one another, the sequences will eventually
become randomized with respect to one another.  Long before they become
randomized they pose difficult problems for practical analysis.

-- 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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