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Darwin-L Message Log 1:166 (September 1993)

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.


<1:166>From ARKEO4@FENNEL.WT.UWA.EDU.AU  Fri Sep 17 20:52:29 1993

Date: Sat, 18 Sep 1993 9:55:27 +0800 (SST)
From: ARKEO4@FENNEL.WT.UWA.EDU.AU
Subject: Re: Lamarkianism in linguistic change
To: darwin-l@ukanaix.cc.ukans.edu

 "Kent E. Holsinger" <HOLSINGE%UCONNVM.BITNET@KUHUB.CC.UKANS.EDU>
noted in a very good anaylsis of the danger of purely allelic defintions of
evolution that
> Including some notion of genetic or hereditary change is important.
				  ~~~~~~~~~~~~~~
> Evolution hasn't happened unless there is some difference between the
> characteristics of ancestors and descendants.

As a biologist/archaeologist who works with evolution in a purely
phenotypic system (human culture), I think the "or" in his statement is
exceedingly important.  Non-genetic hereditary stytems are quite as
amenable to Darwinian analysis as genetic ones (which is no surprise given
that the model was developed well before we knew anything about genetic
systems!).  The important factor in ALL systems capable of evolution, of
course, is selection in terms of fitness (something that seems to have been
a tad overlooked in the "definitions" of evolution posted thus far).  Seen
in these terms, evolution is the result of the selection of hereditable
traits over time (hence, changes in allelic frequencies, etc., are merely
CONSEQUENCES of selection and therefore provide a fairly poor basis for a
definition of it).  Passing note probably should also be made, in this
context,  of the fact that genes, and hence genetic systems, themselves
evolved, no doubt by means of natural selection of pre-genetic hereditable
systems, so selection has temporal precedence over genetics in the
evolution of life itself, and changes in "genetic" systems, as well as genes
as known today, were also a consequence of natural selection.

> If the differences in
> appearance between ancestors and descendants are purely environmental
> modifications, then what we see is organisms developing in a different
> environment, not organisms with different characteristics.

Within my sub-field, this statement would have to be modified to take
account of the fact that variants in pheotypic behaviour can be subject to
selection (and therefore evolve).  Given that culture is THE major
environment which differes between human cultural demes, and given that
differences in traits are both hereditable and subject to fitness values,
then these modifications DO represent organisms with "different
characteristics", not just the "same" organism developing in different
environments.

This relates back to a previous thread on the separation of germ and soma.
I think we should recall that only a small proportion of life on earth
really has this kind of a genetic system: plants, for example, given that
they generate reproductive organs from a somatic meristem, do NOT two cell
lineages.  Hence, somatic mutations in a meristem which have clear
phenotypic advantage, may be selected (as a branch, for example) and the
somatic mutation WILL be heritable.  A nice hueristic here is a non-
variegated branch appearing from a bud in a normally variegated cultivated
tree or shrub: given the increased photosynthetic abilities of the branch,
one will see the green-leafed branch "take over".

In a sense, the evolution of culture is very much representative of the
kind of events which occur in a botanical "tree of life."  I have been
attempting, on and off, to pull together references on studies of somatic
selection in plants and its influence on the kind of evolutionary
opportunities it can create: are there any botanists out there who can help
me with this?

Dave Rindos
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