NOVA Online: Odyssey of Life (see bottom of page for navigation)
see bottom of page for navigation

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,

(go to next letter)
(go to previous letter)
(go to Debate contents)

Odyssey Home | How? | Morphing | Lens
Timing | Creepy Crawlies | Table of Contents

NOVA Home | WGBH Home | PBS Home
Search | Feedback | Shop
© 1996 WGBH