Haeckel in Biology Textbooks

You know this stuff pretty well, so can you do what I would have liked to have done, which is to post chick, mouse and human embryo pictures from the same stage side-by-side, annotated with the number of days *and* the percentage of full term?--Percy

Well maybe not, but saying it don't make it so. This is just one piece of evidence in favour of the idea. There are others. I don't see what's not clear about that. The similarity does provide one piece of evidence indicating that rabbits are more closely related to humans than they are to fish. You highlight 'ARE' as if it sounds definitive.It is no different than saying 'the fingerprints on the weapon is one piece of evidence that indicates that John Smith is the murderer'. It isn't subtly asserting that Mr Smith did the killing, it's just saying that we have one piece of evidence that indicates that this is the case. Nothing specifically (other than 'fishes' which really should be 'fish' ), it's the kind of language you are more likely to find in a primary paper. However, there is nothing wrong with the wording as is so I guess if they thought about it at all it was a stylistic decision. The wording isn't 'this single piece of evidence proves...' but 'this is one piece of evidence that indicates'. And it is. That you are reading things into the sentence that simply aren't there is more an indication of your own indoctrination than an attempt by the textbook authors to do so. It is not the role of the textbook authors to provide an education, just present the course materials. The teacher actually supplies the lesson, using the textbook as a common reference.Indeed, we'd need to see the whole evolution section of the book to know how it handles it. If it presents several pieces of evidence and says that each provides 'one piece of evidence', before ending on a note like 'on their own, these pieces of evidence are interesting but mostly inconclusive and goes on to say that together, they all point in one direction, they are converging lines of evidence - all indicating that evolution did indeed happen and continues to do so...seems to me to a be a fair way of handling the situation. Well, unfortunately for you evolution is as close to unassailable fact as you are likely to come across. Nevertheless, nothing in the wording in question leads to that conclusion.

If you follow my original link you'll see they're examples from a lesson on teaching people how to extract and prepare embryos for study.It was chosen simply as the best examples I could quickly find on the web of actual embryo photos.

I'll give it a shot when I get home from work, it has to be noted though there isn't really a 'same stage' here. You can choose specific criteria, such as somite number, but there are significant differences in the timing of a number of features making any 'same stage' call an educated guess at best. Its not that the embryos don't look similar but that specific features look most similar at different times in the development of each embryo.For a detailed analysis of this problem, specifically mentioning its context in terms of Haeckel's work, see Bininda-Edmonds et al.(2002). This paper is also interesting as the last author is Michael Richardson who is at the same time responsible for perhaps the most detailed scientific critique of Haeckel's work, in specific reference to fraudulent/misleading diagrams, and the best defense of the importance of Haeckel's work in general in the wider context of evo-devo.TTFN,WK

I presume you are referring to the following, which I don't think has been previously posted in this topic: Haeckel's ABC of evolution and development.pdfMK Rich Ardson - MK Blog Rich: The pdf is not currently available, but hopefully will come back.Moose

That was one of the paper's but the paper I originally referenced and several others by Richardson also make similar points.The PDF for that paper, and many others relevant to this subject including those previously referenced upthread, are still available through the wayback machine's cache of the old version of Richardson's site.A particularly relevant illustration which I don't think has been linked to yet is Richardson's alternative embryo series illustration set out like Haeckels but with micrographs instead of drawings. Sadly that one doesn't have the mouse on it. TTFN,WKP.S. Haven't got around to that diagram yet, sorry folks.Edited by Wounded King, : No reason given.Edited by Admin, : Reduce image width.

About Richardson's embryo series, a couple questions.In the top row, what are the large bulbous masses attached to some embryos? Are these a yolk or some equivalent?About the top two human embryos, they're unrecognizable, not only as human but even as embryos. Shown these micrographs out of context I probably wouldn't guess they were embryos, let alone human embryos. In the top one there's no discernable head or tail, while in the middle one I might guess that the bottom structure is a tail, but more likely if someone just handed me that picture and asked me what it was I'd answer, "I have no idea." Primitive sonograms look more human than those micrographs. I guess I'm just very surprised that these two micrographs are so unrecognizable. Something seems very "off" about them.I have to be honest and say that my untrained eye could not use the Richardson series to argue that embryos are more similar at earlier rather than later stages. In fact, the fish seem more similar late than early. I assume a trained eye is necessary to identify the relevant features and note the ways in which they are similar early and describe their growing dissimilarity with development, so maybe someone would like to attempt this?--Percy

Yes, they are yolk sacs. Hmm, I disagree, but I've probably looked at more embryos, human or otherwise. Do you still find this the case with the hi-res version? They are certainly extremely contrasty, the large pools of black look like shadows in most cases but I'm not sure where they are all coming from. One problem is that the human embryos are probably smaller than most of the other ones so the resolution in the original image was probably poorer. Were you confused by the extraembryonic tissues still present in the top row? They are the stuff that looks like a triangular spray of tissue coming from the middle of the embryo.TTFN,WK

Regarding the human embryos, yes, the hi-res version helps a little. The top human embryo now looks like an embryo, though if presented to me out of context I would have guessed a grasshopper after being pulled from an acid bath. The middle embryo just looks like a muddle to me, though.But the more important issue for me is how one would use the Richardson micrographs to argue that embryological development indicates a shared evolutionary history.--Percy

In Message 56 Beretta repeats his claim that Haeckel used artistic license to make embryos across different species appear to have shared characteristics at early stages of development when they do not. He further believes that this is the foundation for much modern acceptance of evolution. He makes a couple other claims that border on the tendentious and even silly, and I'll leave those aside.Haeckel's theory that embryos pass through the adult stages of evolutionary ancestors was false (and sounds incredibly weird to modern ears anyway), and there is evidence that some of his diagrams brought out certain features more clearly than visual evidence would support, but at early stages embryos do possess many common features and development paths that strongly support the conclusion of a common evolutionary history. However, we're finding it very difficult to support this position in an Internet discussion board environment.So I thought I'd see what photographic evidence existed on the web for just one feature, gill slits. Here's the Richardson photograph series that Wounded King posted: I could find no gill slits, but Wounded King supplied a high-res version, and looking at this I think I can discern gill slits in the salmon, the bat and the cat in the photographs in the top row. That's only three out of thirteen. And it does seem somewhat odd to me that I thought I could make out gill slits in more mammal embryos than fish.So is there any photographic evidence on the web that all, or at least most, embryos have gill slits at a very early stage? Demonstrating this seems the minimum requirement for embarking on a rebuttal of Beretta's claim.But even if we find the gill slit evidence on the web, or make it available on the web, a single line of evidence does not a successful theory make. Is there any photographic evidence of other common features? The fish jaw bones that eventually become mammalian middle ear bones perhaps?--Percy

You've already posted an image clearly showing pharangeal arches (aka gill slits) in humans. Labelled 2 & 3. If you'd gone on to the next carnegie stage you can see the 4th arch.

Beretta seems to be on sabbatical, so let me try to argue things from his side.The photographs of chick, mouse and human embryos in my Message 52 do not seem to contain any similarity at the location of the pharyngeal arches. For the human embryo, at the location where these would be are three small bulbous masses (labeled 1b, 2 and 3). At no stage does the chick have any such bulbous masses, and at stage 9.5 the mouse has one. Regarding this one feature I see only slight circumstantial evidence of a similarity between mouse and human, and no similarity at all of the chick with the mouse or human.If I were Beretta I might say that biologists are seeing what they want to see, and I also detect strong hints of a desire to just declare the battle won on this front so they can move on to other less embarrassing evidence.--Percy