[Taxacom] Taxacom Digest, Vol 68, Issue 8
jgrehan at sciencebuff.org
Wed Nov 9 15:53:50 CST 2011
From: Sergio Vargas [mailto:sevragorgia at gmail.com]
Sent: Wednesday, November 09, 2011 4:08 PM
To: taxacom at mailman.nhm.ku.edu; John Grehan
Subject: Re: Taxacom Digest, Vol 68, Issue 8
> by theoretically claimed you mean hypothesized?
If you like.
> well... if you had empirical evidence for the maximal/actual age of a
> clade you would not need molecular dating.
Or any other dating
> I would like to know what the empirical evidence for the maximal age of a
> clade could be?
So would I
> There is no way to demonstrate that a fossil is of maximal age, you can
> only approximate the maximal age of a clade hypothesizing that there is no
> fossil of taxon A that is older that the oldest known fossil of taxon A,
Yes, and even then its just a guess
> or using molecular dating to provide a credible interval for the maximal
> age of the clade given the calibrations (minimal ages) and prior
> distributions for the node ages (to model the maximal age).
> Most authors agree that fossils provide only minimal ages, I don't think
> they ignore this but they base their conclusions on the credible region
> obtained from the analysis, and treat this credible region as an
> approximation to the maximal age of the clade.
Transforming a minimal date maximal according to some 'credible region' sounds more like voodoo.
> Of course some authors really want to have The Date of cladogenesis, but
> with bayesian methods this is getting less common.
A minimum is a minimum is a minimum.
Sergio Vargas R., M.Sc.
Dept. of Earth& Environmental Sciences
tel. +49 89 2180 17929
s.vargas at lrz.uni-muenchen.de
sevra at marinemolecularevolution.org
check my webpage:
check my research ID:
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