Ontogeny Recapitulates Phylogeny

I’m continuing to work my way through Jerry Coyne’s Why Evolution Is True

Coyne talks about how embryos from a variety of animals go through stages: a fish-like stage, a reptilian stage, etc.  According to Coyne and many evolutionists, this is because of the principle that “Ontogeny recapitulates phylogeny”—“that the development of an organism simply replays its evolutionary history” (78).  Coyne gives another example:

During development, the human embryo actually forms three different types of kidneys, one after the other, with the first two discarded before our final kidney appears.  And those transitory embryonic kidneys are similar to those we find in species that evolved before us in the fossil record—jawless fish and reptiles, respectively.

How do we make sense of embryos developing and discarding kidneys?  Would an Intelligent Designer create kidneys that sink into oblivion?  What’s the purpose of that?  Or are the embryos replaying their evolutionary history, demonstrating features of our ancestors, who “evolved before us in the fossil record—jawless fish and reptiles, respectively”? 

I looked for what Answers in Genesis had to say about “Ontogeny recapitulates phylogeny”, and I found this article by Elizabeth Mitchell (not Juliet from LOST), who graduated from the Vanderbilt University School of Medicine in 1984.   Mitchell’s argument is two-fold:

First, according to Mitchell, the idea that “Ontogeny recapitulates phylogeny” was the creation of nineteenth-century zoologist Ernst Haeckel, who “fabricated the embryologic evidence for evolution by fraudulently producing the diagrams to ‘prove’ the theory.”  Mitchell goes on to say that “Reputable German scientists immediately began refuting his evidence, demonstrating that Haeckel had falsified his pictures.”

Second, Mitchell argues that the “gill-slits” in human embryos are not gill-slits.  They don’t function as gills: Never in the course of development does a human embryo absorb oxygen from water as fish do with gills. (The human embryo is fully supplied with oxygen through the umbilical cord.)   And, according to Mitchell, there’s another explanation for what they are:  Actually, they are nothing more than folds in the region of the tiny embryo’s throat. By the 28th day of life, the embryo’s brain and spinal cord seem to be racing ahead of the rest of the body in growth. Therefore, for a time, the spinal cord is actually longer than the body, forcing the body to curl and flexing the neck area forward. (This curled embryo with the long spinal cord is mistakenly accused by some people of having a tail.) Just as many people develop a double chin when bending the neck forward, so the embryo has folds in its neck area due to this flexing.

And so, for Dr. Mitchell, so much for the so-called “gill-slits” and the tail in human embryos!  They’re explicable in light of the human embryos’ response to a rapidly growing spinal cord.

Coyne appears to be aware of certain creationist critiques of evolution.  On page 78, he expresses his own problems with Haeckel.  Coyne denies that embryonic stages “look like the adult forms of their ancestors, as Haeckel claimed”, maintaining instead that they look like the embryonic forms of ancestors.  For example, “Human fetuses…never resemble adult fish or reptiles, but in certain ways they do resemble embryonic fish and reptiles.” 

Coyne also denies that that recapitulation is “strict” or “inevitable”, for “not every feature of an ancestor’s embryo appears in its descendants, nor do all stages of development unfold in strict evolutionary order.”  Moreover, “some species, like plants, have dispensed with nearly all traces of their ancestry during development.”  So, with Coyne (if I’m understanding him correctly), recapitulation does not have absolute rules, but it does occur.

Coyne also dismisses the charge that Haeckel “fudged some drawings of early embryos to make them look more similar than they really are”, maintaining that Haeckel was merely lazy, and that he corrected his error when called to account.

I wonder how Coyne would respond to Mitchell’s other argument.  Would he say that it doesn’t matter that the embryo doesn’t breathe through its gills, since it doesn’t need every feature of its ancestor to show some form of recapitulation?  That it could have gills that it doesn’t use, but the very existence of its gills demonstrates that it’s recapitulating its ancestry?  How would Coyne (or other evolutionists) respond to Mitchell’s argument that the “tail” and the “gill slits” have to do with the embryo’s spinal cord, and are not a “tail” and “gill slits” at all?

On an unrelated note, on page 89, Coyne states: “On the Beagle voyage, Darwin himself discovered fossil seashells high in the Andes, proving that what is now mountain was once underwater.”  This caught my eye because an Adventist pastor once appealed to this as evidence for a global flood, even though he didn’t mention Darwin.  Coyne, however, says that “Lands could rise or sink”, and he expresses his reservations about the biblical Flood story in his book.

About jamesbradfordpate

My name is James Pate. This blog is about my journey. I read books. I watch movies and TV shows. I go to church. I try to find meaning. And, when I can’t do that, I just talk about stuff that I find interesting. I have degrees in fields of religious studies. I have an M.Phil. in the History of Biblical Interpretation from Hebrew Union College in Cincinnati, Ohio. I also have an M.A. in Hebrew Bible from Jewish Theological Seminary, an M.Div. from Harvard Divinity School, and a B.A. from DePauw University.
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2 Responses to Ontogeny Recapitulates Phylogeny

  1. Hi James! I just wanted to say that I’m enjoying your comments on Why Evolution Is True. I may check it out; it sounds very interesting and fairly readable, as are your thoughts about the issues!

    Thanks,

    Josiah

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  2. jamesbradfordpate says:

    Thanks for reading, Josiah! There’s actually more to the book than I’m writing about—for example, he writes a lot about bad design—which he doesn’t think is design, but is explicable in terms of evolution.

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