A review of PZ Myers' review of Chapter 3 of Wells' new book
This post is a follow-up to PZ Myers, the Ann Coulter of Darwinism". Here I will make some specific criticisms of Myers' review of Chapter 3 of Jonathan Wells' new book, "A Politically Incorrect Guide to Darwinism and Intelligent Design." His review was posted in two places, here and here.
I wrote this review because I wanted to see for myself if Chapter 3 of Wells' book is really as bad as PZ said it is. I found serious flaws in the book, but I also found flaws in PZ's review and in a scientific paper written by W.W. Ballard.
This review of PZ's review is divided into three parts: "Obsession with Darwin," "Ernst Haeckel's influence on Darwin," and "Recapitulation theory and vertebrate embryology."
Obsession with Darwin:
PZ's review says,
Another feature of Wells' book, and creationists in general, is the obsession with Charles Darwin.
No one is more obsessed with Charles Darwin than the Darwinists themselves. Just look at the huge Darwin Day Celebration -- I think it's disgusting. They are even linking Darwin and Lincoln just because the two happen to have the same official birthdates -- the two men have virtually nothing else in common. And though Darwinists celebrate Darwin's birthday, many Darwinists feel offended when they are called "Darwinists."
Ernst Haeckel's influence on Darwin:
Wikipedia says of "recapitulation theory,"
First espoused in 1866 by German zoologist Ernst Haeckel, a contemporary of Charles Darwin, the theory has been discredited in its absolute form, although recognized as being partly accurate . . . . The theory claims that the development of the embryo of every species repeats the evolutionary development of that species fully. Or otherwise put: each successive stage in the development of an individual represents one of the adult forms that appeared in its evolutionary history.
PZ quotes from Wells' book:
"…von Baer’s view 'was confounded with and then transformed into' the evolutionary doctrine that the embryos of higher organisms pass through the adult forms of lower organisms in the course of their development. It was this evolutionary distortion of von Baer’s work that Darwin considered the strongest evidence for his theory."
PZ then comments,
There’s that Wells sleight of hand again. Haeckel’s ideas about recapitulation (this idea of embryos passing through the adult forms of ‘lower’ organisms, which even Haeckel did not hold as simple-mindedly as Wells pretends) would be very difficult to find in the Origin of Species, which was published in 1859…note the date of Haeckel’s work.
Probably the best indication that Haeckel did not "simple-mindedly" hold those ideas about recapitulation is that he probably faked the embryo drawings to support those ideas. Wikipedia says,
Haeckel advanced the "recapitulation theory" which proposed a link between ontogeny (development of form) and phylogeny (evolutionary descent), summed up in the phrase "ontogeny recapitulates phylogeny". He supported the theory with embryo drawings that have since been shown to be oversimplified and in part inaccurate, and the theory is now considered an oversimplification of quite complicated relationships. It is thought that Haeckel deliberately faked the images to get more support for his ideas.
PZ also quotes from Wells' book,
"In the 1860’s, German Darwinist Ernst Haeckel (pronounced “heckle”) made some drawings to illustrate this distorted view, and Darwin relied on the drawings in later editions of The Origin of Species and in The Descent of Man (1871)."(my emphasis added)
PZ then comments,
Pore through the Origin, and you won’t find reference to Haeckel’s theory (later editions cite him once), and you certainly won’t find any reliance on his drawings.
PZ quoted the later editions' citation of Haeckel:
Professor Haeckel in his Generelle Morphologie and in other works, has recently brought his great knowledge and abilities to bear on what he calls phylogeny, or the lines of descent of all organic beings. In drawing up the several series he trusts chiefly to embryological characters, but receives aid from homologous and rudimentary organs, as well as from the successive periods at which the various forms of life are believed to have first appeared in our geological formations. He has thus boldly made a great beginning, and shows us how classification will in the future be treated.
PZ asserts that the above paragraph does not mention recapitulation theory, but the statement that in drawing the embryos Haeckel received aid from "homologous and rudimentary organs, as well as from the successive periods at which the various forms of life are believed to have first appeared in our geological formations" might have been a reference to recapitulation theory. Anyway, Darwin does not elaborate here, and if PZ is correct that this is Darwin's only reference to Haeckel, then Wells must have been wrong when he said that Darwin considered recapitulation theory to be the strongest evidence for his own theory of evolution.
As for Wells' claim that Haeckel's faked data is still used in biology textbooks, I have no idea about that.
Recapitulation theory and vertebrate embryology
Here I agree with PZ that Wells quote-mined a scientific paper. However, I think that the paper itself was not accurate and created a lot of confusion.
Here is the quote mine in Wells' book,
It is “only by semantic tricks and subjective selection of evidence,” by “bending the facts of nature,” that one can argue that the early embryo stages of vertebrates “are more alike than their adults.”
And here is the result that Wells' apparently concluded from that quote mine:
The strongest evidence for Darwin’s theory was embryology, but Karl Ernst von Baer, who laid out the laws of development, did not think they supported evolution, and Ernst Haeckel twisted and distorted von Baer’s laws and faked his data to support Darwinism. He was wrong, and the earliest stages of vertebrate embryos do not resemble one another at all, so Darwinism was built on a false foundation, and they’re still using Haeckel’s faked data in our textbooks (emphasis added)
Here is the quote-mined section of the scientific paper, "Problems of gastrulation: real and verbal," by WW Ballard, (1976) Bioscience 26(1):36-39 -- words that I added for clarity are shown in bold:
In the gastrula stage, which comes before the pharyngula stage, we can only say that the embryos of different species within a single taxonomic class are more alike than their parents. However, only by semantic tricks and subjective selection of evidence can we claim that "gastrulas" of species in different taxonomic classes -- e.g., a shark, salmon, frog, and bird -- are more alike than their adults.(words in bold are words that I added for clarity)
It is clear that Wells quote-mined Ballard's scientific paper. The paper said that the gastrula-stage embryos of different species either tend to be more alike or less alike than their parents, depending on whether or not the species are of the same taxonomic class. Wells misinterpreted this as meaning that all early stage embryos of different species are less alike than their parents and that therefore the "earliest stages of vertebrate embryos do not resemble one another at all" (he didn't define what he meant by "earliest"). Wells did not mention the observation that embryos of different species of vertebrates tend to become similar at the pharyngula stage before diverging again. Also, Wells did not explain what all of this has to do with "recapitulation theory." And Wells, Ballard, and PZ often did not make it clear that they were talking just about vertebrates.
However, because the structures of the adult forms and early embryo forms of organisms are radically different, statements that the early embryos of two species are "more alike than their parents" or "less alike than their parents" are often meaningless. I assert that Ballard created tremendous confusion here by speaking in those terms.
I think that Wikipedia has come to the rescue. On a webpage titled "Embryogenesis", Wikipedia says about a very early stage in embryo development,
The zygote undergoes rapid cell cycles with no significant growth, producing a cluster of cells that is the same size as the original zygote. Depending mostly on the amount of yolk in the egg, the cleavage can be holoblastic (total) or meroblastic (partial).
Holoblastic cleavage occurs in animals with little yolk in their eggs, such as humans and other mammals who receive nourishment as embryos from the mother via placenta or milk. On the other hand meroblastic cleavage occurs in animals whose eggs have more yolk; i.e. birds and reptiles. Cleavage thus creates a very uneven distribution of cells concentrating at the animal pole of the zygote.
The different cells derived from cleavage (up to the blastula stage) are called blastomeres.
So according to Wikipedia, the main deciding factor in development at this stage is the amount of yolk in the egg and not -- as Ballard claimed -- the taxonomic class of the species. This webpage describes other differences in embryo development in the very earliest stages.
Finally, Wikipedia says of the pharyngula stage in vertebrates,
The embryonic development of all vertebrates shows remarkable similarities at the embryonic stage called the pharyngula. At this stage they all contain a:
dorsal hollow nerve cord
post-anal tail, and
a series of paired branchial grooves.
So Wells was wrong or misleading here, but I feel that PZ Myers and Ballard were less than clear. As for Wells' claim that recapitulation theory is wrong and therefore does not support evolution theory, Wikipedia says -- as I noted -- that recapitulation theory is now considered to be only partly true. So Wells apparently was partly right, but for the wrong reasons. Also, as noted above, Wells was apparently wrong about Darwin considering recapitulation theory to be the strongest evidence for his theory (assuming that Darwin made no references to Haeckel other than the one PZ reported).
I have often been accused of over-relying on Wikipedia, but what else can I do? I need to get answers quickly in subjects about which I know nothing or almost nothing, and I have generally found Wikipedia to be objective, fair, comprehensive, and accurate.
Labels: PZ Myers