[Taxacom] Hedges /Kumar (eds) The Timetree of Life
Jason Mate
jfmate at hotmail.com
Tue May 17 18:36:21 CDT 2011
Dear Michael,
I should have specified. I meant accurate calibration is impossible if I literally interpret your article (John seems to).
As for the thrust of the paper, I may have misinterpreted the ultimate aim of your paper. Nevertheless I think that the issue is blown out of proportion (maybe not in 2004-2005). In the historical sciences (evolutionary biology, cosmology, climatology, etc) there is an assumed element of uncertainty derived from the data, due to the nature of the data. As such all hypotheses derived are interpreted with caution since new data, which appears at random, can change all the assumptions.
It is possible to guess at a lower bound if the fossil data used for calibrating the phylogenies is interpretated against other fossil data from related groups. So, although a single fossil provides no maximal age, its interpretation against other closely related fossils will provide you with a ballpark maximal age. In the specific case we are discussing, considering the oldest known fossil for the ingroup (37myr) and for rodents in general (KT) it seems reasonable to assume that the maximal age will fall within this range, therefore outside the opening of the South Atlantic and thus not supporting a vicariance scenario.
Best
Jason
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