Keith went on to say, "I think Bob does not understand my point. When I
refer to an upward branching tree I am referring to the splitting of lineages
through time. The top of the tree is the present, and the ends of the
branches are living taxa. Grouping taxa in such a tree beginning from the
top (the present living taxa) results in higher level taxonomic groups
reaching their peak diversity before the lower level taxa contained within
them. This is simply a function of classification procedure. This pattern
is in no way opposed to macroevolutionary theory Darwinian or otherwise."
It's not that I don't understand Keith's point. I just don't accept it.
Evolutionary authors publish paleontological studies of various animal
groups and, without hesitation, use higher level taxonomic categories to
describe their data. No one has told them, as far as I know that their
results are "simply a function of classification procedure." Let me
illustrate my point with several studies. These studies have been around for
a long time.
1. Erwin, Valentine, and Sepkoski, studied the origin and early
differentiation of phyletic lineages of durably skeletonized, invertebrate,
marine fossils found in the early Paleozoic. (_Evol._ 41 (1987):1177-86.)
They summarized their data as follows:
"Most higher taxa were built from the top down, rather than from the bottom
up. The fossil record suggests that the major pulse of diversification of
_phyla_ occurs before that of _classes_, classes before that of _orders_,
orders before that of familiesxthe _higher taxa_ do not seem to have diverged
through an accumulation of lower taxa." (p. 1183).
2. Valentine studied the progression of taxonomic forms in trilobites.
(_Evolution_ San Francisco: Freeman, 1977). His data show that _families_ of
trilobites peaked early in the Cambrian and _genera_ crested late in the
Cambrian. The proportion of _families_ to _genera_ is highest in the early
Cambrian. Later the proportion reverses itself and genera outnumber
families; there are roughly 7.5 times as many genera as families.
Discussing the data Valentine stated, "during the Devonian, although nearly a
hundred new _genera_ appear, only one new _family_ is described. Little or
no real evolutionary advance was taking place" (p. 335). He noted that the
elaboration of genera did not lead very often to novel families, but to mere
variations on an established family theme.
3. Padian and Clemens reviewed earlier studies of the sequence of appearance
of amphibia, reptiles, and mammals (Princeton University Press, 1985), In
discussing the data, they stated, "_Classes_ appeared in the fossil record
some 25 to 30 million years before they achieved maximum _ordinal_ diversity;
after a similar interval, the orders achieved maximum _generic_ diversity."
(pp. 45-6.)
4. About the appearance of birds Feduccia observed, "This explosive
evolution paralleled that of mammals, producing all the modern lineages of
birds within about 10 million years, yielding modern _orders_ by the
Paleocene and Eocene, modern _families_ by the late Eocene or early
Oligocene, and modern _genera_ by the Miocene." (_Science_, 267 (1995):638.)
How do these authors get away with using Linnaean taxonomic classification in
describing and interpreting their data without being criticized? Let me
hazard a guess. It's because they do not explicitly challenge the Darwinian
paradigm with their data. But let them or someone else claim that these
findings challenge the bottom-up hypothesis of Darwin, and they would not
escape disapproval.
Schindewolf, for instance, a highly regarded German paleontologist of the
middle of this century, was criticized by Simpson for "holding quite
literally that the higher categories of a group arise as such before the
lower." Simpson said this should be "taken as as a manner of speaking, a
broad and figurative view of the net result rather than a description of the
process." In another place Simpson said the top-down is "an artifact of
classification." (Simpson, 1953. p. 237)
Ernst Mayr criticized Goldschmidt for holding that, "logic as well as
historical fact tell us that the big categories existed first, and then in
time they split in the form of the genealogical tree into lower and still
lower cate gories" (Goldschmidt, 1952. 91-2). Mayr said "With this
interpretation Goldschmidt has fallen into the error of considering these
categories something natural rather than (particularly in the crucial area of
branch ing) a man-made artifact. Our recognition of a higher category and
its designation, delimitation, and placement in a hierarchy have a large
arbitrary component" (Mayr, 1963 pp. 600-1).
These criticisms are automatic, defensive reflexes. Rather than reexamining
their paradigm in the light of the objective data, these authors attack the
data and the straightforward interpretation of it in order to protect the
evolutionary paradigm. The stakes are high. If the top-down view prevails,
the Darwinian paradigm will suffer irreparable loss.
Peace,
Bob