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Darwin-L Message Log 2:25 (October 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.


<2:25>From mayerg@cs.uwp.edu  Tue Oct  5 14:04:30 1993

Date: Tue, 5 Oct 1993 13:04:29 -0500 (CDT)
From: Gregory Mayer <mayerg@cs.uwp.edu>
Subject: Re: Ease of articulation
To: Jeffrey Wills <WILLS@macc.wisc.edu>

On Fri, 1 Oct 1993, Jeffrey Wills wrote:

>	Let me ask a question of the biologists:
>	A person carries around a variety of codes (languages) and can engage in
> code-switching (shifting to a more polite register in front of an elder, or a
> more formal register in the presence of a teacher, or into a foreign language
> when appropriate). How would you deal with these or parallel them in your
> field? The two languages which a bilingual speaks usually influence each
> other to some extent but for a long period of time these can coexist in the
> same place and in the same speakers (and over many generations). I assume we
> should be treating each of these codes (languages) as the "individuals" in
> our trees and treating language contact as hybridization (as previously
> discussed). The languages not the carriers (people) are the object of study
> and historical tracking. But does it matter that multiple codes are carried
> on the same carriers?

	A parallel situation is well known in biology: nuclear and
organellar genomes.  In eukaryotes (the organisms we all know and love:
trees, birds, butterflies, lobsters), most of the genetic material resides
in the nucleus of the cell, and there are two copies of the complete set
(a condition known as diploidy).  Some of the genetic material, however,
exists outside the nucleus in structures called organelles.  Animals have
mitochondria, and plants have chloroplasts and mitochondria.  The genetic
material of these organelles exists in a single copy form (haploidy).  The
organellar DNAs are inherited independently of the nuclear DNA (you of
course get them from your parents, but they are not linked, in the genetic
sense, to the nuclear DNA).  In animals, there is the further peculiarity
that mitochondrial DNA almost always comes from your mother.  The
organellar DNAs are a separate code from the nuclear DNA (and thus
comparable to a second language) in two senses:

	i) They code for and regulate the production of their own set of
proteins and RNAs which are used in organellar metabolism; and
	ii)  Their actual genetic code is slightly different.  For
example, the code "CGG" means the amino acid arginine in the nuclear
genome, but the amino acid tryptophan in plant mitochondria.

	The two genomes (nuclear and organellar) do interact with one
another, at both a metabolic and evolutionary scale.  Metabolically, the
two work together in total cell functioning.  Evolutionarily, genetic bits
and pieces can be incorporated from one to the other; the general trend
seems to have been for a simplification of the organellar genome, and the
insertion of nuclear sequences into it, but it's gone both ways.

	When making phylogenetic trees from DNA data, a nuclear sequence
is analyzed separately from a mitochondrial sequence, because the two
trees needn't coincide.  Thus, an individual organism's closest
mitochondrial relatives may not be its closest nuclear relatives.
Biologists refer to these trees as "gene trees", and you can make one for
each gene you study, nuclear or organellar. (Technical note: because
organelles are haploid, they, in general, don't recombine, and you would
thus usually combine all sequences from a particular organelle into a
single analysis, rather than one for each gene.)  A population or species
tree attempts to show the history of the populations, in which the nuclear
and organellar genomes coexist.  This need not be identical to any single
gene tree.

	The parallels to language are, I believe, as follows:

1.  The separate genomes (nuclear, organellar) are like separate
languages.  Thus we might study the history of lizard mitochondria and
lizard nuclear DNA as we might study the history of Spanish and Arabic.

2.  Because lizard mitochondria exist in the same bodies as do lizard
nuclei, there can be some borrowing and interchange among them.
Similarly, someone bilingual in Spanish and Arabic (and there were many
such people for many years) might exchange words from one language to the
other.  Such borrowings can take place without obscuring the historical
origin of the language/genome.

3.  The history of Spanish and Arab speakers might be different from the
history of the Spanish and Arab languages, just as the history of lizards
might be different (in the sense of not having isomorphic trees) from the
history of a particular gene/genome.

4.  Since the organellar and nuclear genetic codes (which are sort of like
alphabets) are only slightly different, a more apt linguistic comparison
might be with someone bilingual in Spanish and Portuguese, in which the
alphabets, as well as many of the words and much of the grammar, are quite
similar.

5.  The maternal inheritance of mitochondria might be paralleled by single
sex languages.  Island-Carib men are supposed to have spoken a form of
Cariban among themselves for certain purposes, but the everyday language
of men and women was Arawakan.

	The recognition of such parallels is useful if it allows one or
another discipline to clarify the structure of its questions and
phenomena, or to adopt a problem-solving technique from the other.
Whether _these_ parallels are useful, I do not yet know.

Gregory C. Mayer
mayerg@cs.uwp.edu

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