[Taxacom] Darwin's experiments/Selection pressure (Large dicynodont fossil)

John Grehan calabar.john at gmail.com
Wed Nov 28 10:03:52 CST 2018


Ken,

It was not obvious to me and until Jason says what he means I do not know.

OK - As I said, I was unsure whether it was Darwin or not. But his duck
experiment did not demonstrate trans-oceanic dispersal to account for
different taxa in different regions. His experiment may have shown that it
was conceivable, but whether it was or not is another thing entirely.

Whether selection pressure is a 'perfectly reasonable explanation' is in
the mind of the beholder I guess.

You have not shown that my broad 'complaint' about selection pressure in
general seems problematic. You might see it that way and OK that is your
view.

John Grehan

On Wed, Nov 28, 2018 at 10:50 AM Kenneth Kinman <kinman at hotmail.com> wrote:

> John,
>            I thought it was quite obvious what Jason meant concerning your
> "strict adherence", especially with you bringing up Darwin's experiments
> regarding dispersal.  Trouble is that you seem to have gotten your "classic
> example" wrong.  Darwin actually tested to see if pond snails would adhere
> to the feet of ducks in an effort to demonstrate trans-oceanic dispersal by
> birds.  Seems like appropriate experimentation to me.
>           You seem to be confusing that with his experiments soaking
> garden seeds in salt-water.   And by the way, I believe that Darwin did
> show that some seeds could no doubt survive and germinate after oceanic
> dispersal.
>              ---------------Ken
> P.S.  As for the dicynodont, selection pressure is a perfectly reasonable
> explanation for its large size.  The real question is what type of
> selection pressure, which is why I suggested larger predators was only one
> possibility.  We obviously cannot experimentally test that question
> directly on an extinct taxon, but your broad complaint about selection
> pressure in general does seem problematic.
>
> ------------------------------
> *From:* Taxacom <taxacom-bounces at mailman.nhm.ku.edu> on behalf of John
> Grehan <calabar.john at gmail.com>
> *Sent:* Wednesday, November 28, 2018 8:12 AM
> *To:* JF Mate
> *Cc:* taxacom
> *Subject:* Re: [Taxacom] Selection pressure (Large dicynodont fossil)
>
> Jason,  unfortunately you did not specify how my 'strict adherence to
> orthodox (and you need to specify what that is also) panbiogeography' makes
> my examples problematic at best. Need that for your assertions to be
> informative.
>
> What is the evidence the the dycinodont size is the result of selection
> pressure? You assert that it is 'rooted in the available evidence'. What
> evidence? Need to back your assertions.
>
> Thanks. John Grehan
>
>
>
> On Wed, Nov 28, 2018 at 9:02 AM JF Mate <aphodiinaemate at gmail.com> wrote:
>
> > The fact that all your examples are coloured by your strict adherence to
> > orthodox panbiogeography is problematic at best. This particular example
> of
> > dycinodonts is rooted in the available evidence. Future fossils (or other
> > data) may disprove the hypothesis, but til then it is a perfectly
> > reasonable explanation.
> >
> > Best
> >
> > J
> >
> > On Wed, 28 Nov 2018, 14:09 John Grehan, <calabar.john at gmail.com> wrote:
> >
> > > Imagination is all well and good when grounded in some connected data.
> In
> > > the case of imagined selection pressures there is no testable option
> > that I
> > > know of. Testing itself is always a potentially problematic quality
> > > (falsification can be avoided by attributing incongruent results to
> > either
> > > poor data or to poor theory). And testing itself has to be appropriate.
> > > There is that classic example of Darwin (or someone else) testing
> > survival
> > > of snails in seawater as if their survival demonstrated anything about
> > > whether this was actually operable in the origin of trans-oceanic
> > > distributions involving divergent taxa.
> > >
> > > On Sat, Nov 24, 2018 at 2:13 PM Richard Zander <
> Richard.Zander at mobot.org
> > >
> > > wrote:
> > >
> > > > Hah. Imagination is the groundwork of science. Then you test it.
> > Theories
> > > > derived from tested hypotheses, in the Bayesian sense, are
> predictions
> > so
> > > > well supported that you can bet on such being true with small chance
> of
> > > > failure.
> > > >
> > > >
> > > > -------
> > > > Richard H. Zander
> > > > Missouri Botanical Garden – 4344 Shaw Blvd. – St. Louis – Missouri –
> > > 63110
> > > > – USA
> > > > richard.zander at mobot.org Ofc: +1 314 577-0276
> > > > Web sites: http://www.mobot.org/plantscience/bfna/bfnamenu.htm and
> > > > http://www.mobot.org/plantscience/resbot/
> > > >
> > > > -----Original Message-----
> > > > From: Taxacom [mailto:taxacom-bounces at mailman.nhm.ku.edu
> <taxacom-bounces at mailman.nhm.ku.edu>] On Behalf Of
> > > > John Grehan
> > > > Sent: Saturday, November 24, 2018 10:22 AM
> > > > To: Ken Kinman
> > > > Cc: taxacom
> > > > Subject: Re: [Taxacom] Selection pressure (Large dicynodont fossil)
> > > >
> > > > Ken,
> > > >
> > > > My point was that it was all imaginary. Not science at all. Maybe
> there
> > > > were such selection pressures, maybe there wasn't. It would be like
> > > saying
> > > > that maybe dicynodonts got bigger because they wanted to. Before they
> > got
> > > > so big they obviously survived predation OK or would not have
> continued
> > > > their lineage. Selection pressures can be demonstrated to exist
> within
> > > > populations in the present as an empirical observation. Its another
> > thing
> > > > entirely to invoke its role for a historical change in the fossil
> > record
> > > > when there is not a shred of evidence either way. Its the stuff that
> > > makes
> > > > evolution such bad science (or not science at all) and great fodder
> for
> > > > anti-science folk (so far most of them don't realize how bad or they
> > > would
> > > > have had a field day with this sort of stuff).
> > > >
> > > > John Grehan
> > > >
> > > > On Sat, Nov 24, 2018 at 10:39 AM Kenneth Kinman <kinman at hotmail.com>
> > > > wrote:
> > > >
> > > > > John,
> > > > >        Yet another "fairy tale" complaint?  I'm not sure if your
> > > > > complaint is about the word "selection" or the word "pressure" or
> the
> > > > > word combination.
> > > > >         As for the large dicynodont, selection would not only have
> > > > > protected them from their predators getting larger (survival
> > > selection).
> > > > > It may have also been the result of bigger males having more
> > offspring
> > > > > (reproductive selection), either due to males fighting for females
> > (or
> > > > > possibly females choosing bigger males as mates).
> > > > >         This positive selection for larger size worked very well
> > > > > during the good times.  But when the end-Triassic extinction event
> > > > > came along negative selection would have been particularly hard on
> > the
> > > > > larger animals.  Volcanism and the resulting climate change could
> > have
> > > > > easily resulted in starvation (and perhaps increased disease) in
> many
> > > > taxa.
> > > > >                               --------------Ken
> > > > > ________________________________
> > > > > From: Taxacom <taxacom-bounces at mailman.nhm.ku.edu> on behalf of
> John
> > > > > Grehan <calabar.john at gmail.com>
> > > > > Sent: Thursday, November 22, 2018 6:22 PM
> > > > > To: taxacom
> > > > > Subject: [Taxacom] Large dicynodont fossil
> > > > >
> > > > > So they found a large herbiroous dicynodont fossil that walked in
> an
> > > > > upright manner, similar to large mammals like rhinos and hippos
> that
> > > > > lived between 210 and 205.
> > > > >
> > > > > So to the question of why it was so large it was said " Researchers
> > > > > believe selection pressures—potentially to protect themselves from
> > > > > larger predators—may have been the driver behind their giant size"
> > > > >
> > > > > Good grief. Why is something so large? - selection pressure. Why is
> > > > > something so small? - selection pressure. Why is something in
> > between?
> > > > > - selection pressure. Why do we have to rest science on such fairly
> > > > > tales? - selection pressure. What would we do without selection
> > > > > pressure? What would we do?
> > > > >
> > > > > John Grehan
> > > > >
> > > > > <
> > > > >
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