By Carl Zimmer:
[Hat tip to Brian Switek.]
A commenter named Brad, who is apparently a creationist, left a comment to one of my recent posts. In that post, “Creationist foists “fraudulent” embryo picture on his readers“, I talked about how creationist Brian Thomas ironically used a biologically inaccurate picture of a human embryo to illustrate his article in which he denies the evidence for evolution from developmental biology and implies that all such evidence is based on the supposedly fraudulent embryo drawings 19th century biologist Ernst Haeckel.
Not wanting it to be neglected in the comments section, I have moved my response to Brad up to a full post.
Brad: Wow, evolution is like magic. It turns gills into ears, tonsils, and glands (and part of the larynx).
There is no magic involved in evolution, you’re thinking of creationism, the very heart of which is the claim that living things are the miraculous creations of a supernatural being.
Brad: Calculate the odds…
Since by all available evidence it did in fact happen, the odds are 100%
Brad: Granted, it was a bad choice with the stock photo; however, that’s possibly an oversight vs. the intentional use of known fraudulent drawings for decades in school textbooks.
I would suggest that it was an “oversight” brought on by ignorance of the subject and a lack of curiosity to even check. As for the recycling of Haeckel’s embryo illustrations in textbooks (as illustrations of evidence rather than as a historical reference) this due to the regrettable and all too common laziness on the part of textbook publishers who often recycle not just images but even language as well. See: Stephen Jay Gould’s essay “The Case of the Creeping Fox Terrier Clone” (Gould 1991).
I agree that some* of Haeckel’s drawings exaggerated overall similarity of the embryos they depict and that more accurate illustrations should be used. However, I am unaware of any fundamental anatomical inventions in the illustrations that if corrected would affect the evidence from comparative embryology for evolution.
So, please explain in your own words exactly what anatomical details were altered in Haeckel’s drawings that created evidence for evolution where none exists in actual vertebrate embryos.
Remember, specific anatomical details and in your own words. I don’t want quotes of vague generalities from other people. You’ll note that in my post on pharyngeal clefts at no point did simply I quote some scientists opinion that the pharyngeal apparatus of amniote embryos are homologous to the pharyngeal apparatus of “fish”. Instead I pointed to the anatomical and genetic evidence for this.
If you are going to argue against this, then you are going to have to do likewise. And if you want to present an alternative scientific explanation you are going to have to present something that is logical, coherent, makes reference to the empirical evidence at hand and does not rely on untestable miracles or divine fiat.
Brad: O’Rahilly and Müller stated that ‘the pharyngeal clefts of vertebrate embryos … are neither gills nor slits’.1
I don’t have this reference handy and I don’t know when I’ll get a chance to get to my local university’s science library (whose website says they have it) I was able to find a later edition on Amazon with a free preview which allowed me to get what seems like the relevant section. If the older edition has any important differences please let me know (assuming you have the book and didn’t just cut and past the quote from a creationist and/or anti-abortion website).
Here is the the section which seem to contain Brad’s quote with the part Brad quoted in red:
Recapitulation, the So-Called Biogenetic Law.
The theory that successive stages of individual development (ontogeny) correspond with (“recapitulate”) successive adult ancestors in the line of evolutionary descent (phylogeny) became popular in the nineteenth century as the so-called biogenetic law. This theory of recapitulation, however, has had a “regrettable influence on the progress of embryology” (G. de Beer). The work of Carl Ernst von Baer in 1828 was much closer to the mark. According to the “laws” of von Baer, general characters (e.g., brain, notochord) appear in development earlier than special characters (e.g., limbs, hair). Furthermore, during its development an animal departs more and more from the form of other animals. Indeed, the early stages in the development of an animal are not like the adult stages of other forms but resemble only the early stages of those animals. The pharyngeal clefts of vertebrate embryos, for example, are neither gills nor slits. Although a fish elaborates this region into gill slits, in reptiles, birds, and mammals it is converted into such structures as the tonsils and the thymus. According to the hourglass model of evolutionary development, a conserved pattern of developmental gene expression is linked with considerable resemblance among embryos of different species at a constricted phase, whereas divergence is found earlier and later. Morphological evidence for such a phase, however, is unconvincing (Richardson et al., 1997). (O’Rahilly & Müller 2001, p. 16)
Although there are issues I could take with their description of recapitulation as necessarily being about a strict correspondence between embryos and the adult forms of ancestors or with the short shrift they give the concept of the phylotypic stage (at least in this paragraph), however those are really nuanced points that are not necessary to get into here.
One point I will quibble with regards the presence of slits in certain amniote embryos.
Everything I have seen on the subject indicates that the pharyngeal clefts of some “reptiles” and birds do normally perforate during development and are therefore technically “slits” for a short time before they re-close. This also sometimes occurs in mammals, including humans, though it is not a normal condition. (see my earlier article for links). Also they’ve left out any reference to the larvae of amphibians some of which do develop functional gill slits.
Beyond that, they are absolutely correct, the pharyngeal apparatus of amniotes never function as gills and as I said in one of my earlier posts, I don’t know of any biologist who has ever claimed that they do, save one, the creationist Louis Agassiz.
The Great Satan, Ernst Haeckel, stated in no uncertain terms in his writings that these structures never function as respiratory organs in amniote embryos.
It is not required that the pharyngeal apparatus of amniote embryo function as gills for them to be evidence—not absolute, stand alone proof, but evidence—of their ancestors aquatic nature any more than it is necessary for the hind limb buds of whale embryos to function as working legs for them to be evidence that their ancestors once walked on land.
Brad: Blechschmidt is more forceful, concluding that ‘the so-called basic law of biogenetics is wrong.
The late Erich Blechschmidt (1904-1992) was a scientific outlier (as are some of his followers, i.e. Brian Freeman). That is his views were not representative of developmental biologists as a whole. Creationists love to quote Blechschmidt and other outliers such as Alan Feduccia (who denies that birds are descended from dinosaurs) and Charles Oxnard (who denies that australopithecines are human ancestors) in an attempt to make it seem as if they are tapping into some real controversy amongst scientists. In reality they are just quoting people who are only slightly less on the fringe of science than themselves.
You can find someone with an advanced degree that will say just about anything. For example there is PhD astronomer (and creationist) Gerardus Bouw who argues that the Earth is the center of the solar system.
In this case Blechschmidt (and Freeman) seem to be the source for creationists absurd argument that pharyngeal clefts are merely “flexion folds” caused by the bending of the embryonic neck (Freeman 2001).
As for the biogenetic law, no one is arguing for that. If you read the article you were commenting under you would have seen that I quoted Michael Richardson (a critic of Haeckel) as saying that there are studies which support the recapitulation of individual character transformations, just not whole ancestral stages (Richardson & Keuck 2002, p. 522)
Brad: ” ‘No buts or ifs can mitigate this fact.’ He adds that the gill stage myth is ‘not even a tiny bit correct or correct in a different form…It is totally wrong’. 2 This view is shared by many mainstream embryologists.
No, it is not.
Although among the strongest opponents to Haeckel in recent years, and favourably differing from him by a paramount respect for detail, Blechschmidt resembled Haeckel in several respects: they both were intrepid and very persuasive defenders of their views, they were both artists at heart – witness Haeckel’s illustrations and Blechschmidt’s giantsized models of human embryos – and, most importantly in the present context, they both stuck to some outdated ideas not shared by the majority of contemporaneous biologists: Haeckel remained Lamarckist, defending the inheritance of acquired characters throughout his life, and Blechschmidt strove to maintain the special status of Man by condemning any embryological interpretation or terminology suggesting his descent from other vertebrates. (Sander 2002, p. 531, emphasis mine)
So Blechschmidt apparently had issues with accepting the evolutionary development of humans from other animals. As I said an outlier with an extreme minority view.
Brad: in the end, this is probably an argument evolutionists should give up on.
You’ll understand, I hope, that this evolutionist will not be taking advice on what is or is not valid evidence from a creationist.
Brad: But keep right on with it if you insist, it just makes dogmatic evolutionists sound nuts.
Only to those too ignorant to know better and/or too intellectually lazy to look up the evidence for themselves.
*Note: I am thinking primarily of the first stage shown in the comparative embryo illustration in the 3rd edition of his Anthropogenie (1874)
Freeman, Brian (2001) “The Myth of the “Biogenetic Law”", The American Biology Teacher 63(2):84
Gould, Stephen Jay (1991) “The Case of the Creeping Fox Terrier Clone”, in: Bully for Brontosaurus: Reflections in Natural History, W.W. Norton & Co., pp. 155-167
O’Rahilly, Ronan & Müller, Fabiola (2001) Human Embryology & Teratology, 3rd Edition, Wiley-Liss
Richardson, Michael & Keuck, Gerhard (2002) “Haeckel’s ABC of evolution and development“, Biological Reviews, 77: 495-528
Sander, Klaus (2002) “Ernst Haeckel’s ontogenetic recapitulation: irritation and incentive from 1866 to our time”, Annals of Anatomy 184:523-533
Casey Luskin, the Discoveryless Institute’s resident attack chihuahua, is on a roll. This time he’s gone off on a tangent about a recent find of yet another dinosaur fossil with evidence of protofeathers, Sciurumimus albersdoerferi and dinosaur evolution in general.
Luskin: The media that loyally serve Big Science are at it again, overstating the finds of a scientific paper to promote an evolutionary icon. This time, the icon is feathered dinosaurs, representing the purported ancestral relationship between dinos and birds. (Luskin 2012)
Ah, if only. If only Mr. Luskin’s conspiratorial fantasy were true and the media was that on the ball. The fact of the matter is that defenders of science education like me often cringe at the mischaracterizations and overstatements that come out of the popular media regarding evolution. I am constantly shaking my head and yelling at the TV or radio “no, that’s not what that means at all”, or words to that effect.
I wish I had a nickel (because being underemployed I could really use the money) for every time a silly reporter, while talking about some fossil discovery, described it as “overthrowing everything we thought we knew about the evolution of X”.
That is absolute bollocks, 99% of the time.
If creationists keep spewing nonsense about horses and horse evolution, there may come a day when I run out of literary references and idioms involving horses to play off of in my post titles. But today is not that day.
Before I start I want to promise any regular readers of this blog that despite this being yet another post that is (in part) about creationists and horses, I promise there will be no mention of Hyracotherium this time. No quotes of Richard Owen. No references to hyraxes whatsoever, you have my word.
Once again the source of my ire is the Institute for Creation Research (ICR) who sent forth one of their minions, Christine Dao, to dutifully report what the institute’s “creation scientists” had to say about the recent news that the South Korea is going to be altering their school textbooks to pander to creationists in that country.
Science gained a victory when South Korea’s Ministry of Education, Science and Technology announced last month that textbook publishers will correct editions that contain misinformation regarding evolution.
Yes, absolutely, if there is misinformation in the textbooks we would certainly want to weed that out. The problem is, to a creationist, any of the data that makes up the mountain of empirical evidence supporting evolutionary theory is “misinformation”. Let us examine the two examples of supposed misinformation the South Korean “Ministry of Education, Science and Technology” is planning of removing from textbooks and the “scientific” reasons why the ICR agrees that they should be removed; starting in reverses order with “feathers” (figuratively speaking):
However it is not merely a pigeon that has shuffled off its mortal coil, tis a late pigeon that was once studied by Charles Darwin (Natural History Museum at Tring, Hertfordshire, England), making its image being shared here a matter of course. Photograph by Annie Leibovitz.
[Hat tip to Michael Barton at The Dispersal of Darwin.]
Charles Darwin once said that he thought the evidence from the comparative anatomy of embryos “by far the strongest single class of facts” in favor of common descent (Darwin, 1860) and while it has since been eclipsed by genetics, it remains one of most compelling subsets of evidence for evolution. And perhaps the single most striking detail of the comparative embryology in vertebrates, are the structures colloquially known as “gill slits”.
Embryonic “gill slits” or “branchial clefts” (branchia is Greek for gill) or more properly pharyngeal clefts (grooves, folds, etc.) are part of what is called the “pharyngeal apparatus” found in front (ventral) and sides (lateral) of the head/neck region of all vertebrates in the “pharyngula stage” of development. In “fish”, and the larva of amphibians, these develop into respiratory organs used to extract oxygen from water while in amniotes (“reptiles”, birds and mammals) they are modified into other structures.
Before I go on, a brief digression about “fish”. Throughout this article I will often use “fish” in the generic sense; but it should be noted that the term as it is commonly used—to refer to any vertebrate that swims in the water, has fins and gills—is not a valid scientific classification. This is because the three main types of animals commonly called “fish” —the Chondrichthyes (sharks, rays, skates and chimaeras), the Actinopterygii (ray fined fish, which constitutes the majority of living fishes), and the Sarcopterygii (lobe fined fish, the group from which four legged land animals, i.e. tetrapods, evolved)—are not a monophyletic group. That is they are not very closely related to each other despite some of their outward similarities (like gills). For example the living Sarcopterygii, lung fish and coelacanths share a more recent common ancestor with us (and all tetrapods) than with the other “fishes”.
OK, so the “pharyngeal apparatus” consists of a series of paired pharyngeal arches and fissures which develop on the exterior with a corresponding set of pharyngeal pouches on the inside of the throat, separated from the external fissures by a thin membrane (more on the details in a moment). And in fact the possession of these structures at some point in development, along with a hollow dorsal nerve cord, a notochord and a post anal tail, are the defining characteristics of the phylum chordata to which we and all other vertebrates belong.
Please note that the above illustration is diagrammatic and not intended to be photographically accurate (I have to say that lest I be accused of by creationists of conveying a fraud). Below are actual photographs of both a skate embryo and a human embryo for comparison. Also note: the gill structures in the embryos of Elasmobranch fishes—the subdivision of Chondrichthyes which contains sharks, rays and skates—are much less derived that in other “fishes” and therefore generally more similar to those of amniote embryos than the corresponding structures in the bony “fishes” (which are significantly modified).
The first of the arches, the mandibular arch, forms the jaw in all jawed vertebrates (Gnathostomes). Most vertebrates develop a total of six arches but the full complement is usually only retained into adulthood by hexanchiform sharks. Hexanchiformes are very plesiomorphic which means that they are more like earlier types of sharks. Some species of hexanchiformes even develop a seventh arch. Likewise the extant jaw-less vertebrate, the lamprey, also have seven gill openings.
Please email me your response if possible. I don’t want to categorize myself as a evolutionist or creationist. I was visiting the other website I think it was creationist or similar, your guys arch enemies; anyways I was trying to find proof to support modern man evolving from ape, and they had an extensive article written about the human knee and how it has sixteen parts and minus just one and its useless. Apes have non locking knees and because of their makeup you aparently can’t evolve it into a locking one you have to start from scratch. Evolution and mutations from what I’ve read only allow for small changes no mutation can allow for the formation of a complex organism with sixteen moving parts? The knee would have to be built all at once it couldn’t evolve or it would have no use. How do you suggest that apes dumped their knees and immediately mutated new ones with sixteen brand new parts? I would like to believe it could happen just seems far fetched?
This argument originates from an article (Critical Characteristics and the Irreducible Knee Joint) published in the Creation Ex Nihilo Technical Journal (Vol. 13, No. 2, 1999) by a British engineer named Stuart Burgess.
From my reading of the article it seems to be highly flawed, especially in its almost total lack of discussion on the comparative anatomies of living non-human apes (gorillas & chimps etc.), extinct hominins (australopithecines, early Homo) and modern humans. This lack of attention to comparative anatomy (and physiology) is typical of anti-evolutionists and it leads them to continually talk about the anatomy/physiology of various organisms as if they exist in a vacuum (examples: The woodpecker or The bombardier beetle). They focus on some extreme example of organ or system in a particular species as if it is totally unique to that species. The fact is that when one looks at other closely related species one usually finds that there are variations on the extreme example that the anti-evolutionists have focused upon.
For instance the bombardier beetle that anti-evolutionists often cite is just one species of a whole group of beetles (“Ground beetles”, Family Carabidae) many of which have some variation on a chemical defense mechanism, using the same basic chemicals (which exist in many beetles in varying amounts), but used in differing ways. The specific example that anti-evolutionists cite sprays an explosive mixture out of its abdomen in a fairly well aimed stream at its attackers, however there are other Carabid beetles that spray with less accurate aim, and others that merely excrete bad tasting chemicals out of their abdomens when attacked. There is a whole spectrum from fairly simple to fairly complex defense mechanisms. Anti-evolutionists only talk about the more complex variant.
This discussion of the human knee is another example of this sort of argument in a vacuum.
While I am not an expert in the comparative anatomies of the living non-human apes and humans, as far as I am aware there is no material difference between them. That is, every bone, muscle, ligament, tendon, and cartilage in the human knee has its corresponding representative in the knee of chimpanzees and the other great apes (and presumably in the knee of their concestor). Yes they are shaped somewhat differently. Yes they are proportioned differently. But as far as I know all the same parts are there (if there are any primatologists or physical anthropologists out there, please correct me if I am wrong). [Note: see the 2nd Lovejoy quote provided by Adam Benton in the comments section below.]
As for fossil hominins, the knees of more derived types like Homo erectus (which are either “fully human” or “just apes” depending on what anti-evolutionist you talk to) seem to be virtually identical to those of H. sapiens. As for the knees of the more basal species of Homo (H. habilis) and the australopithecines these become increasingly like those of living non-human apes the farther back in time one goes. Exactly the sort of thing one would predict if humans evolved from an “ape-like” ancestor. The knee of Australopithecus afarensis (which most anti-evolutionists say is “just an ape”) retains a number of “ape-like” features but also has characteristics like those of later hominins including H. sapiens. In other words it is an intermediate form in this regard.
See The ICR and Lucy: Bearing False Witness Against Thy Neighbor for more comparative photos, or refer to any good text on human evolution for comparative illustrations.
Burgess does mention living apes briefly but only to dismiss them as being poor bipedal walkers. However this is a problem for his argument for irreducible complexity (IC), at least as I understand Michael Behe‘s (the person responsible for the recent popularity of this term) definition of the term, in that while the knees of living non-human apes are slightly different in form, and are not as efficient for use in bipedal walking as those of humans, they do work, and they can walk bipedally.
So, assuming that knee joints of the ancestor of later hominins was essentially the same as those of the living non-human apes and could, like them, walk in a bipedal manner at all, then it would be possible for there to be a selective advantage for any slight modifications in their descendants which lead towards an increase in efficiency of bipedalism.
The human knee seems to me to be a poor example of an IC structure.
Some of Burgess’ other arguments just seem nonsensical to me. For example he states:
The knee joint presents a major challenge to the evolutionist because it is unique, and because there are no intermediate forms of joint between a condylar joint and the other two limb joints found in animals and humans – the ball and socket joint and the pivot joint. (Burgess, 1999)
I fail to understand Mr. Burgess’ challenge here. Knee joints did not evolve from elbow, shoulder, or hip joints. Rather knee joints have been knee joints since their origin in the first tetrapods. The same applies to the other types of joints. So why would we expect to find “intermediate forms” between them? That Burgess even posses this as a supposed problem for evolution demonstrates a significant lack of understanding about evolutionary theory and the fossil record.
It is a curious thing that Behe’s principle of IC as an argument for design turns the traditional argument from design on its head. It used to be argued that those features of organisms that seem perfectly sculpted to suit their needs, or seem well designed from an engineering point was evidence for design. Now, under Behe’s IC principle of design, it doesn’t matter how clunky, ungainly, and poorly designed from an engineering point of view something is, it only matters that it is supposedly irreducibly complex.
Apparently the “Designer” under this new design “theory” is a (supernatural) cosmic Rube Goldberg.
Ken Ham, president/CEO of Answers in Genesis (USA), which is headquartered in Kentucky has attacked an exhibit at the Kentucky Horse Park on horse evolution in a recent post to his blog “Around the World with Ken Ham” and it is yet another glittering example of creationist scholarship.
“The Lord hath delivered him into mine hands”.
The reason this came to mind was that it is clear from his comments that he has not bothered to educate himself on the subject and is just mindlessly repeating tired, long refuted creationist clichés on the subject of horse evolution. In other words, he’s lobbing softballs at defenders of science like me.
Alright, without further ado let’s saddle up and ride forth into the mind of Ham:
I am going to give another wag of the finger, this time to Scientific American. They posted a number of paintings of reconstructions of various extinct “horses” in a picture gallery titled “Ancient Miniature Horses”, which includes an entry for the famous “dawn horse”, Hyracotherium.
However, the problems lies not in the painting, which is probably a reasonable guesstimate of what Hyracotherium might have looked like in life but rather with the blurb of information included with the painting:
Hyracotherium This genus of small early horse roamed the early woodlands of Asia, Europe and North America some 55 million to 45 million years ago. It was already larger than Sifrhippus, weighing about 22.7 kilograms. But when Richard Owen first discovered Hyracotherium in 1876, it was so diminutive that he thought it was some unknown hyrax species, a group of extant mammals that live in Africa and the Middle East.
No, no, no, a thousand times no! It is bad enough when creationists claim that Hyracotherium is merely a hyrax (rather than a ancestral horse) and claim that Richard Owen thought so as well but to have a venerable science publication like Scientific American falling into the same pit of misinformation is extremely vexing.
This seemed apropos:
[Hat tip to the WhyEvolutionIsTrue channel on YouTube.]