Darwin-L Message Log 7:59 (March 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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<7:59>From LANGDON@GANDLF.UINDY.EDU  Thu Mar 17 07:40:20 1994

Date: Thu, 17 Mar 1994 07:40:20 -0600
From: "JOHN LANGDON"  <LANGDON@GANDLF.UINDY.EDU>
To: darwin-l@ukanaix.cc.ukans.edu
Subject: Re: Humanoid fossils in Time

In message <m0phASn-000Sm6C@eros>  writes:
> Maybe I'm *really* missing something, but the "single vs. multiple origins"
> question seems to be being discussed as though the options were
>
>   (a) whatever mutations were necessary to get to _sapiens_ from _erectus_
> all occur in one place and then spread; or
>
>   (b) all these things happened independently at a number of spatially (and
> somewhat genetically) separated places.
>
> An option that intuitively seems at least worth serious consideration is
> what I *think of* as a variant of (b)---that at least some mutations
> happened only at one or very few places, but that different critical
> mutations happened at *different* places, so that the gene flow (that
> resulted in _sapiens_ all over) was critically multidirectional.

Your a / b dichotomy sounds like a replay of Calton Coon's version of
multiregionalism-- long since dismissed. Here is my interpretation of the
issue. Both camps recognize or can accommodate a single origin for any relevant
mutation(s). They differ in how that mutation(s) became fixed in the descendent
species. Was it

(a) by gene flow; i.e., interbreeding with subsequent natural selection, etc.,
occurring within populations and always favoring the new mutation(s); or

(b) by actual population replacement in which the mutant population completely
displaced and replaced other populations.

The major issue here is whether these older populations contributed
significantly to future gene pools. Some morphologists are saying yes; those
studying mitochondrial DNA are saying no.

JOHN H. LANGDON                email   LANGDON@GANDLF.UINDY.EDU
DEPARTMENT OF BIOLOGY          FAX  (317) 788-3569
UNIVERSITY OF INDIANAPOLIS     PHONE (317) 788-3447
INDIANAPOLIS, IN 46227

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