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Out of Africa

Keith Robison robison at ribo.harvard.edu
Sat Nov 16 18:26:21 EST 1991

lamoran at gpu.utcs.utoronto.ca (L.A. Moran) writes:

>Keith Robison (robison at nucleus.harvard.edu) writes,

>      1. mtDNA sequence analysis (see ref. below) generates a tree in which 
>         one must climb eight nodes from the root before finding a branch 
>         which contains non-African sequences on both sides of the branch 
>         (the tree was rooted with a chimpanzee sequence)."

>This is an interesting point but I don't see why it is relevant. Let's assume
>that Homo sapiens sapiens arose in Eurasia and that the original population
>split in two with half migrating to Africa. At some later point in time
>another group from Eurasia also moved to Africa. In fact, there may have been
>several such incidents over time.

>Keith, can you construct an Out-of-Africa senario that is so obvioulsy more
>reasonable and more simple? Any senarios that I can think of still require
>many migrations between continents. For example, an early population
>would have had to migrate out of Africa but some descendents of this group 
>returned. Or, several distinct populations left Africa at different times. 

>Laurence A. Moran (Larry)
>Dept. of Biochemistry
>University of Toronto

Using the Vigilant et al (1991, Science 253:1503-7) data, and trying to
minimize the number of migrations, I get the following table:

Origin assumption		  Africa		Somewhere else
Migrations from origin		    5			      2  

Back-migrations to origin	    7			     26
Total migrations		   12			     28

Does this answer your question?

Keith Robison
Harvard University
Program in Biochemistry, Molecular, Cellular, and Developmental Biology

robison at nucleus.harvard.edu


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