The Case for a Creator, Chapter 3
Ernst Haeckel died
a hundred and fifty almost a hundred years ago [fixed - thanks, Alex!], but the creationists won’t let him rest in peace. In this section, Wells again exhumes these old bones and takes a few kicks at them, and imagines that by doing so he’s brought the entire edifice of modern evolutionary biology crashing down.
If you’re not familiar with Haeckel, here’s a bit of background. Ernst Haeckel was a nineteenth-century biologist, one who lived at about the same time as Charles Darwin. He’s best remembered for his dictum “ontogeny recapitulates phylogeny”, meaning that a developing embryo retraces the evolutionary history of its ancestors – i.e., a human fetus first passes through a fish-like stage, then an amphibian-like stage, then a reptile-like stage, and so on. Haeckel is also infamous for defending this claim by using his own drawings of developing embryos, which turned out to be faked to exaggerate the stages he claimed were there.
What makes this more than a hundred-year-old cautionary tale is that creationists claim that Haeckel’s drawings are still presented in textbooks as evidence for evolution. Here’s how Wells puts it:
“They’re still being used, even in upper-division textbooks on evolutionary biology. In fact, I analyzed and graded ten recent textbooks on how accurately they dealt with this topic. I had to give eight of them an F. Two others did only slightly better; I gave them a D.” [p.48]
Strobel chimes in, declaring that he too remembers being taught about these drawings as evidence for evolution, and that “anger was brewing inside of me” [p.48] as he realized that he had been duped.
I’ll give Strobel the benefit of the doubt and assume he’s confabulating memories. Wells, however, I don’t intend to treat so charitably: again, he is lying, making statements which he must know are false. P.Z. Myers quotes one of the books which Wells disparages by claiming that it is “resurrecting Haeckel”, Campbell’s Biology:
The theory of recapitulation is an overstatement. Although vertebrates share many features of embryonic development, it is not as though a mammal first goes through a ‘fish stage’, then an ‘amphibian stage’, and so on. Ontogeny can provide clues to phylogeny, but it is important to remember that all stages of development may become modified over the course of evolution.
Myers also cites a post listing a large number of other college textbooks that point out the problems with Haeckel’s hypothesis. Out of 15 books reviewed, only one presents recapitulation uncritically – and that one is from 1937!
All of Wells’ indignation is a smokescreen, intended to cover up an uncomfortable point: namely, vertebrate embryos do pass through a stage, called the phylotypic stage or the pharyngula, in which they all look very similar. Haeckel’s biogenetic law was a hypothesis intended to explain that observation. By criticizing one particular faulty hypothesis, Wells hopes to cast doubt on the observation itself.
Wells repeatedly attacks textbooks for making claims such as “the early embryos of most vertebrates closely resemble one another” [p.50], implying that this is an endorsement of Haeckel. In fact, this is a completely true statement, referring to the phylotypic stage. These patterns of embryological development are real, and they do not disappear just because one particular explanation of their origin is falsified.
To take the measure of Wells’ mendacity, realize that when he gives “grades” to textbooks, he lowers the grade if the book contains actual photos of embryos. He considers this a “misleading” tactic when it comes to making the case for evolution. Why, we wouldn’t want to show people what embryos actually look like, do we? It might give them the wrong idea!
This fact explains Wells’ great annoyance over the term “gill slits”, a lay term for branchial arches, which are a structure common to embryos at the phylotypic stage. Wells insists, despite the name, that these are not gills [p.51]. This is true, but unfortunately for him, he then goes on to undermine his own argument:
“In humans, the ridges become one thing; in fish, they become gills.” [p.51]
It’s correct to say that human embryos do not have gills. (That would be Haeckel’s biogenetic law.) But the more important point is one that Wells, unintentionally I’m sure, has illustrated: vertebrate embryos pass through a stage where they are very similar, and the same structures that exist in the embryonic forms of many species develop into completely different adaptations in the adult forms of those species. This is a phenomenon that evolution provides a good explanation for. How, or whether, ID can explain it is a question never raised in this book.
Other posts in this series: