Seattle, July 10, 2023 Dear MorphMetters,
This is a followup to my email of January 15, which directed
you to a preprint posting on arXiv of a manuscript I had
just submitted to my favorite journal, Evolutionary Biology.
The text has changed somewhat since then, mainly in
response to a very constructive journal review.
The revision was accepted and has just been posted to the internet
on the journal's website as
https://doi.org/10.1007/s11692-023-09607-2
The article is Open Access, so you are free to download it if you want.
The title remains "Reworking geometric morphometrics
into a methodology of transformation grids."
Its basic thrust is that now is the
time to totally rethink the combination of Procrustes analysis
and thin-plate splines, the two foundations of today's most
common GMM toolkit, as we apply them in studies of shape differences at
large scale (growth gradients, for example, or the kind of
processes that used to be called "orthogenesis").
This requires three major changes of method,
each one reanimating the spirit of contributions far earlier than
my own. A first change, echoing D'Arcy Thompson (1917), restores
the reading of the deformation grid per se -- the bending
and spacing of its collection of curves -- to the report of a
morphometric contrast, cause, or effect. For that purpose (this is
the second change), the rotation steps in the Procrustes procedure
should be set aside in favor of
the two-point shape coordinates of Francis Galton (1907).
And the third change, echoing Peter Sneath (1967),
complements the thin-plate spline with polynomial regression grids
and the residuals from them, in order to expedite our understanding
of the deformations these diagrams are intended to illustrate.
A fourth stage in this methodological metamorphosis,
a novel and (by me, at least) unanticipated multivariate analysis for
large-scale features of landmark configurations,
is the topic of a later preprint of mine,
DOI:10.1101/2023.03.23.533997, that I announced in an email to
you all on March 25. A revised version of _that_ has
just been submitted to this same journal, Evolutionary Biology,
and of course if it is published I'll let you know.
As always, I welcome any comments you may have, positive
or negative, on these ideas. You may send them to me
at either of my academic addresses (below) or post them to
this Google group.
For the abstract of the paper, please see the accompanying .pdf.
Thanks for reading this.
Fred Bookstein
[email protected], [email protected]
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to.morphmet.7.10.23.pdf
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