Re: ORIGINS: Phyletic Change
Thu, 5 Sep 1996 06:54:06 -0400

Keith Miller objected to my thesis that phyletic lineages develop from the
"top down" and did not evolved from the "bottom up." He said that the
"pattern, however, is generated by the classification process itself." The
top-down pattern is the necessary result of applying a hierarchical
classification retrospectively to a diversifying evolutionary tree, he said.
Miller's response is completely in line with the way evolutionary authors
have attacked the top-down interpretation of the fossil record starting with
Simpson and Mayr, more than forty years ago.

The top-down, hierarchical pattern, however, is not forced upon the data. It
is not generated by the classification process as Miller claims. The pattern
is rather, a true and valid reflection of the hierarchical way that nature is
organized. The pattern starts 530 million years ago. Fifty modal body plans
suddenly appeared in the Cambrian explosion. They are the founders of all
the complex, animal groups of modern design that exist today or ever have
existed. They are classified at the top level, Phyla and Classes, the
highest taxonomic level in the animal kingdom by Briggs et. al (1994). No
fossil trail of increasingly higher taxonomic forms leading from the
Precambrian to the explosion of Cambrian animals has been found.

What happened after the Cambrian explosion? Here is an example of
post-Cambrian data that supports the top-down pattern that emerged. In a
study of a large sample of marine invertebrates, Erwin, Valentine and
Seposki, (1987) reported finding 11 different Phyla. The Phyla peaked 25
million years after their first appearance early in the Cambrian. The Phyla
differentiated into 62 Classes, which peaked 55 million years after the peak
of the Phyla. The Classes differentiated into 307 Orders, the next lower
taxonomic level, which peaked 110 million years after the Class peak.

Here is how the authors summarized their data: "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
families...The higher taxa do not seem to have diverged through an
accumulation of lower taxa." This conclusion is based on the fossil record,
as the authors stated, not on a hierarchical classification system. Their
conclusion is all the more significant in that they are committed to the
evolutionary paradigm, yet they were able to look at the data from the fossil
record and conclude that the top-down pattern prevailed.

There is no hint here that this conclusion is "simply an artifact of the
retrospective way in which the classification system was constructed
beginning with modern extant species" as Miller claims. Moreover, his claim
that the "origin of higher taxa [arose] through evolutionary processes at the
population and species level" is challenged by the authors' claim that "The
higher taxa do not seem to have diverged through an accumulation of lower

My paper (Bottom Up vs. Top Down) presents several additional studies that
show a similar pattern in the fossil record of trilobites, amphibians, birds,
mammals. Moreover, Rensch, an early Neo-Darwinian author, stated that
classes are twice as old as orders, which are twice as old as families, and
families are 1 1/2 times as old as genera (1959). These all support the
top-down direction of phyletic change.

Furthermore, after summarizing the top-down nature of fossil data,
Goldschmidt, as far back as 1952, went on to say, "Can this mean anything
but that the type of phylum was evolved first and later separated into the
types of the classes, then into orders, and so on down the line? This
natural, naive interpretation of the existing hierarchy of forms actually
agrees with the historical facts furnished by paleontology. The phyla
existing today can be followed farthest back into remote geological time.
Classes are a little younger, still younger are the orders, and so on until
we come to the recent species which appear only in the latest geological
epochs. Thus 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 categories."

I conclude from these studies that the top-down direction of phyletic
development is confirmed by paleontological data of the fossil record.

That is not the way, however, Darwin viewed the organization of nature. He
made a diagram of an evolutionary tree and explained it as follows: "Thus
the diagram illustrates the steps by which small differences distinguishing
varieties are increased into larger differences distinguishing species. By
continuing the process for a greater number of generationsxwe get eight
species marked by the letters between a14 and m14 all descended from (A).
Thus, as I believe, species are multiplied and genera are formed." (Origin,
p. 112.)

He continued, "I see no reason to limit the process of modification, as now
explained, to the formation of genera alone.xThese two groups of genera will
thus form two distinct families, or orders, according to the amount of
divergent modification supposed to be represented in the diagram. And the
two new families, or orders, are descended from two species of the original
genus, and these are supposed to be descended from some still more ancient
and unknown form" (Origin, p. 115).

Darwin's diagram betokens the origin of the bottom-up hypothesis, and has
been maintained without exception by all later evolutionary authors,
Goldschmidt excepted. It started out as a hypothesis. Darwin was rather
tentative about it. It has become, however, a central, non-negotiable
doctrine of the evolutionary paradigm. It is no wonder that evolutionary
authors from Simpson and Mayr through Eldredge and Gould challenge the
top-down thesis. The disconfirmation of Darwin's bottom-up hypothesis would
deal a crippling blow to the Darwinian paradigm. The hypothesis, however,
has never been confirmed by paleontological data. Miller's arguments along
with those of other evolutionary authors are abstract. They fail to support
them with paleontological data.

The empirical support given to the top-down direction of phyletic development
and the lack of paleontological data to support Darwin's hypothesis provides
a serious challenge to the Darwinian paradigm.


Bob DeHaan