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Re: Cladistics (was Sci. Am. - present)



Christopher Brochu <cbrochu@fmppr.fmnh.org> wrote:
> I'm not sure why this is.  In the vast majority of cases, DNA sequence
data
> and morphology tell  you more or less the same thing.  Molecular data are
> no less subject to selective pressures, and levels of homoplasy given
data
> sets of the same size are no different.
> 
> 10 years ago, the question was "should it be molecules or morphology?"
> Today, the answer is "yes!"

Yes, but there are certainly examples where our morphologically-based
phylogenies have been disproven by DNA sequence data.  For example, recent
DNA research has shown today's elephants to share a common ancestor with
hyraxes, manatees, dugongs, aardvarks, golden moles, and (I love this one)
elephant shrews.  Nobody predicted such a family.

It would appear that we will never get the DNA sequence data required to
put our morphologically-based dinosaur phylogenies to a proper test. 
Perhaps the comparison of preserved proteins in dinosaur bone (if such can
be confirmed) will provide us with some much-needed additional data.  In
lieu of this, paleontologists and paleo enthusiasts must be aware that we
can only do our best to interpret an incomplete puzzle, and our present
methods are not infallible.

Having said this, I still cast my lot with the cladists, but I am mindful
that some things are (at least for the time being) unknown and unknowable.

 Ralph Miller III <gbabcock@best.com>

"Trust in Allah, but tie up your camel."