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Darwin-L Message Log 7:58 (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.


<7:58>From kent@darwin.eeb.uconn.edu  Thu Mar 17 07:19:08 1994

Date: Thu, 17 Mar 94 08:20:27 EST
From: kent@darwin.eeb.uconn.edu (Kent Holsinger)
To: darwin-l@ukanaix.cc.ukans.edu
Subject: Re: H. erectus into H. sapiens (was re: Humanoid...)

Ken Jacobs writes:
>Part of the difficulty in envisioning "H. erectus evolving everywhere
>_simultaneously_ into H. sapiens" is caused by semantics.  Because the
>start point of the single lineage (on this view of the matter) has been
>given a name which is distinct from the _end-point_ of the lineage (i.e.,
>H. erectus versus H. sapiens), one cannot help but tend to see what is
>called H. erectus as being very distinct from what is called H. sapiens.
>Yet in the middle somewhere, at the arbitrary point which divides the two
>taxonomic units, there will be virtually no difference.  The difference
>between a 0.25Mya "H. erectus" and a 0.24Mya "H. sapiens" will be 0.01My
>and not much else.  The taxonomic nightmare which is late Middle
>Pleistocene Europe attests to just this phenomenon.

Actually, that's not the problem *at all* as I see it.  The question, is
whether _H. erectus_ and _H. sapiens_ are related anagenetically or
cladogenetically.  For those not familiar with the terms, let me explain.
Imagine the following tree of relationships:

         A    B      C
          \  /      /
           \/      /
            D     /
             \   /
              \ /
               E
               |
               |

Species A and B share a more recent common ancestor with one another (D) than
either shares with C (E).  Anagenesis is evolutionary change that happens
*along* the branches, i.e., from E to C, E to D, D to A, or D to B.
Cladogeneis is the process that leads to splitting of lineages, i.e., the
process that takes the single lineage leading to E and splits it into two, one
leading to A and B, the other to C.  Similarly, cladogenesis occurs at D
producing two lineages.

The multiregional hypothesis suggests that _H. erectus_ and _H. sapiens_ are
related anagenetically.  The single origin hypothesis suggests that they are
related cladogenetically.  As I said in my early reply to Bayla Singer (though
not in these words), I know of no case other than the origin of human beings
where evolutionary biologists have postulated (in the last twenty years at
least) an anagenetic relationship between two widely distributed species.

-- Kent

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