Sunday, February 11, 2007

Haeckel's Embryos

Art, in a comment, links to PZ Myers' blog, containing analysis of whether textbooks really do use Haeckel's drawings in a misleading way. Unsurprisingly, the conclusion presented is that they aren't widely so used.

I don't have access to 15 biology text books. However ...

Miller and Levine have written one of the standard biology textbooks. On their website, they say:
British embryologist Michael Richardson and his colleages published an important paper in the August 1997 issue of Anatomy & Embryology showing that Haeckel had fudged his drawings to make the early stages of embryos appear more alike than they actually are! As it turns out, Haeckel's contemporaries had spotted the fraud during his lifetime, and got him to admit it. However, his drawings nonetheless became the source material for diagrams of comparative embryology in nearly every biology textbook, including ours! So, what have we done? Well, we fixed it! In 1998 we rewrote page 283 of the 5th edition to better reflect the scientific evidence. Our books now contain accurate drawings of the embryos made from detailed photomicrographs
So there is an acknowledgement here that the drawings were used by them, and were in widespread use in "nearly every biology textbook" (contra PZ's website, which implies of textbooks generally by reference to the sample examined: "only a minority used Haeckel's figure at all.").

I also have a copy of Alberts et al. "Molecular Biology of the Cell" from 1983. Obviously this predates the Richardson paper, but it is within the 1923-1997 range talked about on PZ Myers' blog. It says:
The Vertebrate Body Plan is First Formed in Miniature and Then maintained as the Embryo Grows
The embryo at the stage when the somites are forming is typically a few millimetres long and consists of about 105 cells. While we have been speaking thus far of Xenopus, the scale and general form are much the same for a salamander, a fish, a chick, or a human (Figure 15-15). Later these species of embryo will grow to be very different in size and shape, but for the moment they can all be seen to share the basic vertebrate body plan. The details will be filled in later as the embryo grows.

Alberts et al., "Molecular Biology of the Cell", p.824, 1983
The text for Figure 15-15 says:
Comparison of the embryonic development of a fish, an amphibian, a bird, and a mammal. The early stages (above) are closely similar; the later stages (below) are more divergent. The earliest stages are drawn roughly to scale; the later stages are not. (After E. Haeckel, The Evolution of Man, London, 1879)

Alberts et al., "Molecular Biology of the Cell", p.825, 1983
The pictures of the earliest embryos are basically simplified versions of Haeckel's drawings, and have little in common with the "actual appearance of vertebrate embryos" which Wells gives on "Icons of Evolution", p.92.

Douglas Futuyma has also written one of the definitive textbooks on evolutionary biology. According to Wells, the 1998 edition used Haeckel's drawings - and in 2000, Futuyma "explained that before reading the critic's accusation he had been unaware of the discrepancies between Haeckel's drawings and actual vertebrate embryos... So Futuyma, a professional evolutionary biologist and author of a graduate-level textbook, did not know about Haeckel's faked drawings."

How strong are the claims made against Haeckel's drawings by proponents of ID? Are they saying, as PZ implies on his blog, that textbooks aren't critical of Haeckel's proposition that "ontogeny recapitulates phylogeny"? No. Neither do they dispute that there are similarities between the two. ISCID (Intelligent Design website) says:
There are indeed similarities between ontogeny and phylogeny. However, Haeckel's embryo drawings produced to support his theory overemphasized certain similarities and de-emphasized dissimilarities.
The thrust of the charge in this case is that the case for evolution is being supported with evidence that is known to be discredited. There is no dispute that there are developmental similarities in embryos - just that the hand is being overplayed, and misrepresented - as Wells says,
It was Futuyma who mindlessly recycled Haeckel's embryos in several editions of his textbook, until a "creationist" criticized him for it. And it was Gould who (despite having known the truth for over twenty years) kept his mouth shut until a "creationist" (actually, a fellow biologist) exposed the problem.

"Icons of Evolution", p.109
So the post on PZ Myers' blog is factually doubtful, and also misses the point.