[Taxacom] Molecular evidence (in 2017) supports my 2014 theory about rafting killifish

[John Grehan]

  Hi Ken,

I never said "there is a constant molecular clock over long periods of
time."

OK, but it seemed that way to me when you objected to the idea that a
molecular clock placing origins so far back using a tectonic calibration.
All I pointed out was that if the molecular divergence rates are not
constant then the extended extrapolation could be erroneous.

"However, I do think it is ridiculous to imagine fluctuations so extremely
wild that they could support the idea that a taxon 10 million years old (or
perhaps slightly older) could have arisen in the Mesozoic. "

But HOW do you know it is only 10 million years old in the first place? If
it's a fossil calibrated estimate then the age is a minimum that sets no
maximums. That is the basic point. Why don't you get that?

"Panbiogeographers seem to be far too quick to challenge the many cases of
long-range dispersal, and imagining over and over again that there are
fossils out there just waiting to vindicate their skepticism."

Actually that is quite incorrect. Fossils are not required to vindicate the
'skepticism'. And it's not just a matter of skepticism. It is based on a
huge amount of studies over the last 70 years, and much of the more recent
work using molecular systematics results. If you wish to contest, with very
specific reference, any particular studies or the studies in general please
feel free to do so. Happy to comment on that.

 Most people view it as wishful thinking, obsessive, and very annoying.

Not applicable. You misrepresent (perhaps unintentionally)
panbiogeographic analysis. And whether or not is annoying - that is your
call. All of us can be annoyed by a different viewpoint.  I'm annoyed at
the insistence of molecular systematists misrepresenting fossil calibrated
ages as actual or maximal. But so what? What one feels personally has
nothing to do with scientific merit.

Cheers, John Grehan



On Fri, Jan 1, 2021 at 4:01 PM Kenneth Kinman via Taxacom <
taxacom at mailman.nhm.ku.edu> wrote:

>           I never said "there is a constant molecular clock over long
> periods of time."  There could well be fluctuations.  However, I do think
> it is ridiculous to imagine fluctuations so extremely wild that they could
> support the idea that a taxon 10 million years old (or perhaps slightly
> older) could have arisen in the Mesozoic.  I assume this is just one reason
> Smissen et al. challenged Heads' critique in 2005.
>         Panbiogeographers seem to be far too quick to challenge the many
> cases of long-range dispersal, and imagining over and over again that there
> are fossils out there just waiting to vindicate their skepticism.  Most
> people view it as wishful thinking, obsessive, and very annoying.
>
> ________________________________
> From: John Grehan <calabar.john at gmail.com>
> Sent: Friday, January 1, 2021 10:56 AM
> To: Kenneth Kinman <kinman at hotmail.com>
> Cc: taxacom at mailman.nhm.ku.edu <taxacom at mailman.nhm.ku.edu>; Rob Smissen <
> SmissenR at landcareresearch.co.nz>
> Subject: Re: [Taxacom] Molecular evidence (in 2017) supports my 2014
> theory about rafting killifish
>
> Hi Ken,
>
> The idea that there has to be a constant molecular clock throughout the
> phylogenetic history of a group is not an empirical finding. It is a model
> of evolution that may not be true. We see this in the morphological aspect
> of molecular genetics where different groups separated or dislocated by a
> tectonic feature show different levels of morphological divergence (for
> example with the NZ Alpine fault dislocation where correlated distributions
> may be conspecific or species level differences even after more than 20
> million years. So the panbiogeographic implication of tectonic correlation
> is that this provides an approximation of age for the correlated groups. It
> has no necessary implication for the upper limits of their phylogenetic
> origins involving other sister taxa. If molecular clock models
> incorporating a tectonic correlation result in unacceptable results that
> does not invalidate the tectonic correlation. But it does raise questions
> about the molecular model.  Nothing ridiculous about it at all. This has
> been commented on in the panbiogeography literature.
>
> Whether or not the acceptance of geological correlations as an empirical
> source of evidence for vicariance is 'extreme obsession' or not is neither
> here nor there. Fact is that fossil calibrated divergence estimates are
> minimums and no one, including yourself, has demonstrated anything to the
> contrary. And now what has been drawn to attention is the larger and more
> problematic issue as to whether there is a constant molecular clock over
> long periods of time. Like priors, molecular clocks are also theoretical
> models (and there are different models) and open to question or refutation.
> I would like to see you, Ken, show how a constant molecular clock is
> substantiated as empirical evidence (I guess you won't based on your past
> reluctance concerning fossil calibration, but I might as well ask).
>
> Cheers, John Grehan
>
>
> On Fri, Jan 1, 2021 at 10:59 AM Kenneth Kinman via Taxacom <
> taxacom at mailman.nhm.ku.edu<mailto:taxacom at mailman.nhm.ku.edu>> wrote:
> Hi Rob,
>         Thank you for the work you have done on this subject in spite of
> panbiogeographer's criticisms.  I just read your critique of Heads, 2005
> (Smissen et al., 2005 "Dating nodes on molecular phylogenies: older or
> younger than the Earth itself?"
>         The following is certainly a valid criticism of Heads: "If this
> was then extrapolated to the tribal‐level divergences (around 0.4
> substitutions per site) within the Caryophyllaceae that we used as a
> calibration for our dating, then the Caryophyllaceae are projected to be in
> excess of 10 billion years old."
>        It would take an extremely wild fluctuating molecular clock for
> panbiogeographers to explain this away.  And yet all Grehan could suggest
> in his latest post was:  "Only if the 'clock' was constant throughout.
> Maybe it's not."  That is a rather ridiculous statement, and certainly
> provides none of the "empirical evidence" that he is always demanding.  It
> only provides yet another example of their extreme obsession with
> vicariance.
>
> https://onlinelibrary.wiley.com/doi/10.1111/j.1096-0031.2005.00077.x
>
>
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