My attention was recently drawn to an article published in Nature some
years ago that concerns two populations of black-backed jackals studied
with the intent of evaluating their relatedness using the widely accepted
procedure of examining differences in the mtDNA of the two groups. The
ranges of the two populations studied were within a few km of one another,
easily within contact in a single generation. The results of this study
suggested there are some things we do not yet understand about the use of
mtDNA for determining time of separation within populations and speciation
events. The article in Nature, by Wayne and Jenks (1991 vol 351, pp565-8)
presents data contradictiong the firmly held conviction of some authors
that mtDNA is a reliable chronometer. This data has never been adequately
addressed to my knowledge. In this article Wayne shows evidence that the
mtDNA in these two populations of black-backed jackals whose ranges were
disparate by only a few km. differed enough that the time of separation
(calculated on the basis of the time for accumulation of the mutations
using standard assumptions about rates of base replacement) for the two
closely associated populations was greater than the time estimated for the
existence of the species itself. This evidently calls into question some
of the assumptions that are made in calculating time using mtDNA.
Numerous other citations could be listed including a number that show
paternal contamination that make the whole issue of the usefulness of mtDNA
in calculating anything useful fall apart, as yiour citation above suggests.