Darwin-L Message Log 2:5 (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.

<2:5>From LANGDON@GANDLF.UINDY.EDU  Fri Oct  1 09:12:10 1993

Date: Fri, 1 Oct 1993 09:12:10 -0500
To: HOLSINGE%UCONNVM.BITNET@KUHUB.CC.UKANS.EDU, darwin-l@ukanaix.cc.ukans.edu
Subject: Re: A parallel between linguistic and biological evolution?

> > If you cut off contact between two halves of one speech community,
> > different changes will occur in the two groups' speech.
> Almost the same thing can be said in biology:
> If you cut off contact between two halves of a species, different changes
> will occur in the two groups.
> If you subsitute the phrase "gene flow" for "contact," you have (roughly)
> Ernst Mayr's classical description of the way in which allopatric
> differentiation occurs.  In fact, I wonder whether both of these principles
> are both instances of a single more general principle.

In my perspective, what species and languages have in common is that they are
both properties held by populations and not individuals. A species should not
be considered adequately defined by a single individual (although of necessity,
that is where taxonomists often have to begin). Language is not language unless
it is used to communicate among individuals. Therefore when the population is
divided and becomes two populations, its property (e.g. language) also becomes
two independent entities (two languages). Whether or not these two populations
or two languages are different from one another is best answerable in
retrospect after divergence has become more visible.

>  Does it seem reasonable to conclude that
> the following is true (I'm not entirely sure. I'm just throwing it out for
> discussion.):
> 1) Define a population as a group of interacting entities that
>  a) reproduces itself and
>  b) has the property that newly arisen entities within the population
>   have characteristics that resemble, but do not necessarily duplicate,
>   the characteristics of the population.
> 2) If such a population is divided into two or more groups, so that
> individuals in a group interact only with other individuals in their group
> and not with individuals in other groups, then
>  a) the newly produced groups are populations and
>  b) the characteristics of these populations will tend to diverge from one
>   another through time.
> Actually, it occurs to me that I really have *two* questions about the above
> scenario.  First, is it true?  (I think I can make a pretty good argument for
> its truth in biology, but I'm not so sure about other fields.)

This is true if and only if we assume the changes between generations (under 1b
above) will not be the same in both groups. It is easy to see why these are
different in both species and languages-- variation within populations and some
degree of randomness of changes. However, this assumption probably should be
written into the model above.

> Second, if it is true, is it interesting?  Does it really tell us something
> informative, or is it so broad and general as to be uninformative?

Probably it is not informative for biologists and linguists who already
understood this principle. But perhaps there are other systems that we have not
though of as belonging to this class-- e.g. academic "schools" of theory.

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