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How Did We Get Here?
Letter 3
Kenneth R. Miller, November 23, 1996
Dear Phillip,
I agree it would be great fun to debate your book, Behe's book, or my books,
but if we can, I'd like to keep discussion here focused on evolution itself.
As you note, the splendid Nilsson photographs show striking similarities in
embryonic development between humans and other vertebrates. However, I was
surprised to see you knock down Ernst Haeckel's "Ontogeny recapitulates
Phylogeny" argument as a straw man for evolution. Haeckel was wrong, as the Life magazine article carefully points
out. But it is an even greater mistake to maintain that development teaches us
nothing about evolution.
The development of any animal is controlled by the unfolding of an internal
genetic program. Haeckel believed that changes could only be added at the end
of that program, the source of his well-understood mistake. Mutations that
affect structure or timing can in fact occur at any part of the program,
including the beginning. Because of this, there is no reason to be surprised
at the fact that adaptations to the vastly different sizes of mammalian and
avian eggs have produced "radically dissimilar" patterns of cell division in
the early embryo. The chicken embryo develops on top of a huge store of
nutritional yolk, which it gradually surrounds with an egg sac. The human
embryo has no such store, and must implant in the uterine wall to obtain
nourishment. Once both embryos surmount these early challenges, the rest of
their development is remarkably similar, and that's precisely the point.
There is a marvelous consistency to the evidence for evolution. Mammals
possess a developmental pattern clearly modified from earlier forms, their
fossil history abundantly documents their evolution from a group of reptiles
more than 100 million years ago, and DNA sequence comparisons show the very
same relationships suggested by the fossil and developmental evidence. I
challenge you to present an alternative explanation consistent with this
interlocking set of facts from so many completely different sources.
Curiously, you claim the fossil record is "pervasively anti-Darwinian," and
demand "common ancestors of the animal phyla." Demanding specific ancestral
forms from the oldest and rarest fossil formations is good strategy, but poor
science. In fact, if evolution were incorrect, I should not be able to name
any ancestors for modern animals. But, as you know, had you asked for the
ancestors of horses, elephants, or whales the fossil record provides them in
expanding abundance. Isn't this exactly the evidence you claim is lacking?
I'm not sure what you mean by "anti-Darwinian," but the fossil record certainly
isn't anti-evolution!
Finally, I'd like to ask you a specific question on human origins. The New
York Times this week (11/19/96) reported an important hominid fossil that helps
to complete the picture of human evolution. If you reject evolution, how do
you interpret this and the scores of other hominid fossil finds? The facts of
fossil morphology persuasively argue that these organisms were indeed human
ancestors. I look forward to your response.
With Best Wishes,
Ken
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