Does Ontogeny Recapitulate Phylogeny?

Of course, there's not a one of us who hasn't heard this old, debunked chestnut (I even used it to pull off a win at a Knowledge Bowl meet in high school.) But is it really not true? Certainly the field of evo-devo attempts (to my understanding) to analyze developmental pathways as potential clues to the evolution of a species. Furthermore phenomenon such as neoteny suggest that evolutionary histories and an organisms development are related.Now, I'm not suggesting that an organism literally recapitulates its evolutionary history prenatally. But maybe it's time to be a little less dirisive of the idea that ontogeny recapitulates phylogeny? Thoughts?

When I first heard "ontology recapitulate phylogeny" it was explicitly said that this means that the early embryos of vertebrate species are similar, that many features that are clearly the same in the embryos of different species will develop into adult structures that are homologous - i.e. the pharyngeal pouches developing into gills in fish but into the jaws of mammals. This is true.I did hear the claim that the embyo supposedly passes through the entire evolutionary history of the particular species, but it was always pointed out that this stronger statement is false. So when I hear that this is a controversey in the evolution/creation argument, I, for one, don't understand what the fuss is all about. The truth is, ontology does recapitulate phylogeny, in the weaker but well-supported sense. I don't know of anyone who claims the stronger statement.

for anyone that wants to see the Carnegie Stages from 7 to 23 (click here)

---

we are limited in our ability to understand
by our ability to understand RebelAAmerican.Zen[Deist

I think strictly speaking, ontogeny recapitulates phylogeny does mean that the embryo will pass through stages similar to the adult stages of its ancestors, and I think this is what Haeckel proposed. But the weaker claim is absolutely true. I hate in when creationists say "ontogeny doesn't recapitulate phylogeny" when you make the weaker claim , as if that is a rebuttle.A good site for videos and pictures of embryology and discussions on this subject is NOVA (as always).NOVA Online/Odyssey of Life/Timing is EverythingOrganisms with a recent common ancestry are going to have similar developmental pathways. Here's a picture of a chimp and human embryo.[This message has been edited by JustinCy, 03-25-2004]

Ontogeny doesn't recapitulate at least cartilaginous fish phylogeny.
In the best case, we could observe a reduced insight of the immediatly primitive form. Nothing more.
As far as I know, I'm not creationist.Denesha

Hi crash.As Chiro pointed out, Haeckel's strong claim, which he stated as the "Biogenetic Law", is that phylogentically new traits are "added" to the ancestral version. IOW, that during development an individual embryo successively passes through all the adult forms of its ancestors - from the origin of a single cell to the modern organism. This was quite patently wrong, and even at the end of the 19th Century it was being called (loudly) into question. The only bit that remains valid is the observation that most vertebrate classes share many common features really early in development. Things start to diverge fairly quickly however. The other major problem with Haeckel was that he appears to have over-emphasized certain traits in his famous drawings that were not valid in order to prove his point. (Well, that and the fact that later he founded Monism, which says a lot about the person, although nothing about the "law" itself). I don't think anyone is derisive of him beyond that - except for creationists - and he stimulated a great deal of new research, which is a good thing for science. I think overall he advanced the field, but was mostly wrong.

Q do you have a "homogenous" idea of "adult" for both plant and animal? It appeared that when trying on hoxology for size Gould was able to get away with TWO ideas of modern maturity.

If I understand what you're asking, then my answer would be "not really". I'm not up on evo-devo, focusing more on ecology and conservation biology (so much to read, so little time). I know that there are several major problems with the ontogeny recapitulates phylogeny thingy, especially in relation to plants (e.g., selfing), heterochrony and paedomorphs (like some of the Ambystoma spp). IOW, the Biogenetic Law doesn't hold very often - if at all.In any event, IIRC Gould used hox to show that Goldschmitt might have been on to something, not Haeckel.

That sounds correct. I only wonder what to make of Mayr's ambivalence in ONE LONG ARGUMENT as to H(aeckel) and G(ould)later in WHAT EVOLUTION IS then but again relating Mendel and Darwin is still but a chore rather than a pay stub.

Ont. does not recapitulate Phyl. in the strictest meaning of the phrase. However, various steps in overall phylogeny are present in embryonic development, and there are eerie similarities between the development of most vertebrates. This includes ossification centers, patterns of ennervation, and development of organs. Haeckel proposed that each step in embryo development EXACTLY copied the evolutionary history of that species. This is false. But there are important clues about genetic heritage and evolutionary pathways hiddden in embryo dev. In fact, embryo dev. is sometimes used to construct phylogenetic trees, especially with closely related species. Ont recap. Phyl. is still useful, but nonetheless falsified as a biologic law.

The Creationist dispute of whether ontogeny recapitulates phylogeny has never seemed one of any merit to me. Maybe my education is lacking, but I've always understood "ontogeny recapitulates phylogeny " to be more of a general principle rather than a strict law. Embryo development in the more recent orders quite obviously passes through stages closely resembling older orders, such as the oft mentioned gill stage in mammals. Since evolution takes a make-do approach, I assumed that features of earlier orders manifested themselves in a variety of ways, some developing fully and then being reabsorbed, like the tail for tailless mammals like ourselves, and others developing less fully or even just barely before making a turn toward something more mammalian, like the gill slits.I've never read Haeckel, but if he actually claimed this general principle was an invariant law, and if he claimed the gill slits were actual gills, then I guess he was wrong.About the accuracy of Haeckel's drawings, I think it was Gould who made a very interesting point. He showed drawings by professional artists who accompanied Napolean's early 19th century campaign in Egype side-by-side with modern photographs of the same objects. Just as striking as the similarities (those artists were *good*) were the differences. For example, one common difference was the number of and expression of scroll lines. Gould (if it was Gould) argued that when faced with the problem of making many drawings quickly that artists were often forced to capture as much as possible the essence of the object rather than every particular detail. I tend not to accept this argument, because from what others have said I gather Haeckel's own words indicate he thought his drawings very accurate.But whether Haeckel was right or wrong at the level of detail anyone cares to evaluate his work, the fact of the matter is that in general ontogeny absolutely does recapitulate phylogeny. Quite clearly, embryo development follows a course similar to evolutionary ancestors until a certain point is reached, and the particular degree of the similarity will vary from one characteristic to the next as the vagaries of evolution having to make do with what's available are felt.--Percy

Comeon LM do you really think they are "eerie" or is that only meant for deep shaking in the online community?

quote:

---

Comeon LM do you really think they are "eerie" or is that only meant for deep shaking in the online community?

---

From the stand point of special creation, the patterns in development are eerie. Perhaps "eerie" harkens back to the days when this information was still new (my favorite was cranial nerve development between vertebrates). Just to get a little more life out of my Behe thread, the movement of jawbones into the middle ear during mammalian development is also quite striking given the evolutionary history of those bones. Ontogeny is not like watching the film "Evolution over the last 100 million years" but it does have some nice highlights. If you like I could change "eerie" to "curiously intriguing".

No need to change. I am waitng for the day that heirarchy theory explains those nerves interms of data from different levels of organization for that is how I think through the different number of nerves of salamanders and frogs but as long as levels of selection philosophy is working more on emergent fitness it is unlikely that Behe's notions will break the current understanding or less of it in biophysical genetics. take care.

I have read (some of) Haeckel - he sadly mixed a true statement of the relation with what he called (IIRC) The Fundamental law of Ontogeny which is a literal and strong statement of Ontogeny recapitulates Phylogeny and is false.Haeckels admits (in response to his critics) in the forward to the second edition that his drawings are not photographically accurate. But maintains that they are diagramatically correct in a manner equal and similar to the manner in which any diagram is correct.I think he is broadly correct in this claim; while his diagrams do omit some details and emphasise others they do not do so to an unacceptable degree and the features he draws attention to do exist.