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dinosaur behaviour: other aspects
cf. Julia Parrish & William Hamner, eds., 1997. Animal
groups in three dimensions: how species aggregate
(Cambridge University Press), 378pp
I highly recommend, as a basis for discussion in this
forum, these chapters:
Kevin Warbuton, Social forces in animal congregation:
interactive, motivational, and sensory aspects
Frank Heppner, Three-dimensional structure and
dynamics of bird flocks
L.M. Dill, C.S. Holling, L.H. Palmer, Predicting the
three-dimensional structure of animal aggregations
from functional consideration: the role of information
Herds/flocks as information centres is my
Another interesting springboard for discussion in this
forum: Richard Lewontin, 2000, The triple helix
(Harvard University Press), 136pp, which I have
finally read at the urging of Alan Brush. A
fascinating exegesis of various concepts, although his
knowledge of dinosaurs is somewhat hampered. He writes
on page 65: Indeed, the largest dinosaurs mitigated
the effects of gravity by living partly submerged in
water, another consequence of the genes they carried.
He is speaking of sauropods and hadrosaurs...and the
scenario is one I find no evidence for, contra Henry
He does, however, offer gems of concise observations:
All species that exist are the result of a unique
historical process from the origins of life, a process
that might have taken many paths other than the one it
actually took. Evolution is not an unfolding but an
historically contingent wandering pathway through the
space of possibilities. Part of the historical
contingency arises because the physical conditions in
which life has evolved also have a contingent history,
but much of the uncertainty of evolution arises from
the existence of multiple possible pathways even when
external conditions are fixed. ...Populations subject
to identical selective conditions may arrive at quite
different evolutionary endpoints, so that the
observation that two species differ is not prima
faciae evidence that they were adaptively
differentiated. There are many cases in which related
groups of species have a variety of forms of the same
basic basic feature, but in which there seems no way
to provide a special story of selection for each form.
This leads to a discussion of ceratopsians.
He further writes (page 91):
Selection cannot occur for a particular characteristic
if some genetic variation in the direction of that
characteristic is not present in the population. It is
useless to argue that natural selection would favor a
vertebrate with two wings in addition to its four
limbs, because no such variation in the genes
controlling early segmentation has occurred, or if it
has it has not been of a kind that would allow regular
development to proceed.
I would also like to emphasize his cogent redefinition
of evolutionary processes as being not "adaptation"
etc., which would divorce a taxon from its
environment, but as "the process of construction"
(page 48). He writes (pages 54-55):
...organisms not only determine what aspects of the
outside world are relevant to them by peculiarities of
their shape and metabolism, but they actively
construct, in the literal sense of the word, a world
around themselves....organisms not only determine what
is relevant and create a set of physical relations
among the relevant aspects of the outer world, but
they are in a constant process of altering their environment.
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