Darwin-L Message Log 45: 11–22 — May 1997
Academic Discussion on the History and Theory of the Historical Sciences
Darwin-L was an international discussion group on the history and theory of the historical sciences, active from 1993–1997. Darwin-L was established to promote the reintegration of a range of fields all of which are concerned with reconstructing the past from evidence in the present, and to encourage communication among scholars, scientists, and researchers in these fields. The group had more than 600 members from 35 countries, and produced a consistently high level of discussion over its several years of operation. Darwin-L was not restricted to evolutionary biology nor to the work of Charles Darwin, but instead addressed the entire range of historical sciences from an explicitly comparative perspective, including evolutionary biology, historical linguistics, textual transmission and stemmatics, historical geology, systematics and phylogeny, archeology, paleontology, cosmology, historical geography, historical anthropology, and related “palaetiological” fields.
This log contains public messages posted to the Darwin-L discussion group during May 1997. It has been lightly edited for format: message numbers have been added for ease of reference, message headers have been trimmed, some irregular lines have been reformatted, and error messages and personal messages accidentally posted to the group as a whole have been deleted. No genuine editorial changes have been made to the content of any of the posts. This log is provided for personal reference and research purposes only, and none of the material contained herein should be published or quoted without the permission of the original poster.
The master copy of this log is maintained in the Darwin-L Archives (rjohara.net/darwin) by Dr. Robert J. O’Hara. The Darwin-L Archives also contain additional information about the Darwin-L discussion group, the complete Today in the Historical Sciences calendar for every month of the year, a collection of recommended readings on the historical sciences, and an account of William Whewell’s concept of “palaetiology.”
------------------------------------------ DARWIN-L MESSAGE LOG 45: 11-22 -- MAY 1997 ------------------------------------------ DARWIN-L A Network Discussion Group on the History and Theory of the Historical Sciences Darwin-L@raven.cc.ukans.edu is an international network discussion group on the history and theory of the historical sciences. Darwin-L was established in September 1993 to promote the reintegration of a range of fields all of which are concerned with reconstructing the past from evidence in the present, and to encourage communication among academic professionals in these fields. Darwin-L is not restricted to evolutionary biology nor to the work of Charles Darwin but instead addresses the entire range of historical sciences from an interdisciplinary perspective, including evolutionary biology, historical linguistics, textual transmission and stemmatics, historical geology, systematics and phylogeny, archeology, paleontology, cosmology, historical anthropology, historical geography, and related "palaetiological" fields. This log contains public messages posted to Darwin-L during May 1997. It has been lightly edited for format: message numbers have been added for ease of reference, message headers have been trimmed, some irregular lines have been reformatted, and some administrative messages and personal messages posted to the group as a whole have been deleted. No genuine editorial changes have been made to the content of any of the posts. This log is provided for personal reference and research purposes only, and none of the material contained herein should be published or quoted without the permission of the original poster. The master copy of this log is maintained on the Darwin-L Web Server at http://rjohara.uncg.edu. For instructions on how to retrieve copies of this and other log files, and for additional information about Darwin-L and the historical sciences, connect to the Darwin-L Web Server or send the e-mail message INFO DARWIN-L to firstname.lastname@example.org. Darwin-L is administered by Robert J. O'Hara (email@example.com), Center for Critical Inquiry in the Liberal Arts and Department of Biology, University of North Carolina at Greensboro, Greensboro, North Carolina 27412 U.S.A., and it is supported by the Center for Critical Inquiry, University of North Carolina at Greensboro, and the Department of History and the Academic Computing Center, University of Kansas. _______________________________________________________________________________ <45:11>From firstname.lastname@example.org Fri May 23 12:35:09 1997 From: "Neil Haave" <email@example.com> To: firstname.lastname@example.org Date: Fri, 23 May 1997 11:28:45 +0000 Subject: Re: Ontogeny recapitulates... > Tzvi Langermann > email@example.com > I would be very interested to learn about the current standing of Ernst > Haeckel's dictum, "Ontogeny recapitulates phylogeny." > More specifically, then, I would like to know (1)how the rule is judged > today--true, false, useful, irrelevant, etc., and (2)the basis for this > judgment--a consensus of scientists, particular experimental or observational > evidence, or something else. From what I understand, the biogenetic law is not accepted as Haeckel defined it; that is that organisms go through the adult stages of their evolutionary ancestors during their development (ontogeny). However, a revision of this is coming into vogue in biology. Organisms share stages of ontogeny with their phylogenetic ancestors up until the point they diverge evolutionarily. Hence, they share developmental stages but do not progress through the adult stage of every one of their evolutionary ancestors. The references that J. Ahouse refers to regarding heterochrony is a theory which attempts to explain this process through differential timing of when (& therefore where) different developmental stages occur in the embryo and also the duration of the developmental stage. Many (eg. reviewed in Gilbert et al 1996, see especially pp 362-363) see this as ONE way of bringing developmental biology into the modern evolutionary synthesis of genetics and natural history which occured earlier this century. S.F. Gilbert, J.M. Opitz, & R.A. Raff. 1996. Resynthesizing evolutionary and developmental biology. Dev. Biol. 173:357-372. Cheers Neil ************************************************** Neil Haave, Ph.D., Associate Professor Division of BIO/CHE, Augustana University College Camrose, AB, Canada, T4V 2R3 voice: (403) 679 1100, fax: (403) 679 1129 mailto:firstname.lastname@example.org http://www.augustana.ab.ca/ ************************************************** _______________________________________________________________________________ <45:12>From email@example.com Fri May 23 14:23:04 1997 Date: Fri, 23 May 1997 12:22:55 -0700 From: firstname.lastname@example.org Subject: Re: Ontogeny recapitulates... To: email@example.com, firstname.lastname@example.org The shortest and sharpest analysis of the biogenetic law is, probably, S.J.Gould's chapter "Heterochrony" in "Keywords in Evolutionary Biology" edited by Evelyn Fox Keller and Elizabeth LLoyd. The 1982. book "Embryos, Genes and Evolution" by R.Raff and T.Kauffmann has a nice introductory historical chapter. Also, Haeckel is analyzed at length in Adrian Desmond's "Archetypes and Ancestors"(1982), and in chapters 5-9 in M.Ruse (1996) "Monad to Man". There is an interesting chapter by Sue Taylor Parker, "Anthropomorphism is the null hypothesis and recapitulationism is the Bogeyman in Comparative Developmental Evolutionary Studies" in R.W.Mitchell, N.S.Thompson, H.Lyn Miles (Eds.) "Anthropomorphism, Anecdotes, and Animals", SUNY Press, 1997. To see how embryologists differ from evolutionary biologists, just open an introductory embryology textbook to see how, albeit slightly reworded, Haeckel's biogenetic law still lives. In science-fiction, this theme has been explored in: Burroughs, E.R. - Land That Time Forgot Huxley, A. - After Many a Summer Dies a Swan Capek, K. - War with the Newts Beljajev, A. - Man-Amphibian Blish, J. - A Case of Conscience Sturgeon, T. - The Golden Helix and the new Kessel's "Corrupting Dr.Nice" (1997) has as he main character a paleontologist who studies dinosaur heterochrony directly, by travelling to the Jurassic... I hope this helps. Bora Zivkovic North Carolina State University _______________________________________________________________________________ <45:13>From email@example.com Fri May 23 09:25:14 1997 Date: Fri, 23 May 1997 07:22:54 +0000 To: firstname.lastname@example.org From: "Phillip E. Johnson" <email@example.com> Subject: Ontogeny recapitulates... Tzvi Langermann began this discussion by saying: >>I would be very interested to learn about the current standing of Ernst >>Haeckel's dictum, "Ontogeny recapitulates phylogeny." To which Jeremy Ahouse responded: >A fine place to start is Gould, S. J. (1977) Ontogeny and Phylogeny. >Harvard Univ. Press: Cambridge * * * Gould opens that book by reminiscing that he was taught in school that "ontogeny recapitulates phylogeny" -- several decades after that formula had been discarded by science. He continues with this observation: "I have had the same, most curious experience more than twenty times: I tell a colleague that I am writing a book about the parallels between ontogeny and phylogeny. He takes me aside, makes sure that no one is looking, checks for bugging devices, and admits in markedly lowered voice: 'You know, just between you, me, and that wall, I think that there really is something to it after all." Last year the U.S. Public Broadcasting System did one of its "Nova" TV programs featuring Lennart Nilsson's photographs of the developing human embryo, comparing human embryos with embryos from other vertebrate species. Although the PBS program did not use words like "Haeckel" or "recapitulation," the whole thrust of the program was to suggest to viewers that human embryology is a kind of re-run of human evolution. A Life Magazine story on the Nilsson photos said that, although science has repudiated recapitulationism, features like human embryonic "gill slits" provide a "hazy" picture of evolutionary history. The web site of the Paleontology Museum at the University of California (Berkeley) has a page on Haeckel (http://www.ucmp.berkeley.edu/history/haeckel.html), which concludes: >The "law of recapitulation" has been discredited since the beginning of >the twentieth century. Experimental morphologists and biologists have >shown that there is not a one-to-one correspondence between phylogeny >and ontogeny. Although a strong form of recapitulation is not correct, >phylogeny and ontogeny are intertwined, and many biologists are beginning >to both explore and understand the basis for this connection. That last sentence is pretty murky, but the public may reasonably take it to mean that a "weak" form of recapitulation is gaining ground among biologists, and so "there really is something to it after all." Phillip Johnson Professor of Law University of California, Berkeley _______________________________________________________________________________ <45:14>From firstname.lastname@example.org Fri May 23 16:22:43 1997 Date: Fri, 23 May 97 17:23:02 -0400 To: email@example.com From: "Jeremy C. Ahouse" <firstname.lastname@example.org> Subject: Re: You shall know them Ah... the list is back... Any of you who take Joshua Lederberg's suggestion; "Let's start a discussion some months downstream of Vercors' main propositions - but wait till more folks have had a chance to catch up" will have to find a used copy. I found mine at an internet used book store. Make sure that you look for either the title "You Shall Know Them" or "Borderline" (the British title). cheers, - Jeremy _______________________________________________________________________________ <45:15>From email@example.com Sat May 24 17:27:39 1997 Date: Sat, 24 May 1997 17:27:34 -0500 (CDT) From: firstname.lastname@example.org (Paul A. Nelson) Subject: Re: Ontogeny recapitulates... To: email@example.com Neil Haave wrote: >Organisms share stages of ontogeny with their phylogenetic ancestors >up until the point they diverge evolutionarily. Hence, they share >developmental stages but do not progress through the adult stage of >every one of their evolutionary ancestors. In the literature, this postulate is often referred to as "von Baerian," as opposed to "Haeckelian," recapitulation, and -- in general, following the authority of Gould (1977) -- is held by many authors to be a reliable generalization. It is not. It is just as false as Haeckelian recapitulation. (I don't like the role of curmudgeon, but I've been waiting for the evolutionary developmental biologists on this list, if any, to speak up.) Indeed, von Baerian recapitulation is completely misnamed, and, as a summary of developmental patterns, would be unrecognizable to von Baer himself. As Raff (1996, 6-8) notes: Von Baer intended his 'laws' to make the theory of recapitulation untenable. His results showed that fancied resemblances across phyla, such as those proposed by Serres, were unfounded. The body plans revealed by development were clearly specific to each of the great 'embranchments' defined in 1812 by Georges Cuvier....Von Baer provided no support for homologies between body plans because to him, development represented a common theme within each embranchment. Unfortunately, after it was misnamed, von Baerian recapitulation found a comfortable living in the secondary literature as a misrepresentation of metazoan development, and thus will probably be with us as a biological myth indefinitely. Take, for instance, early embryonic similarity in the vertebrates. Ayala -- in the _Encyclopedia Britannica_, alas -- sketches the received view as follows (1988, 987): Vertebrates, from fishes through lizards to humans, develop in ways that are remarkably similar during early stages, but they become more and more differentiated as the embryos approach maturity. The similarities persist longer between organisms that are more closely related (man and monkey) than between those less closely related (man and shark). Common developmental patterns reflect evolutionary kinship. But this is simply not the case. The earliest developmental patterns in vertebrates are actually very diverse: Indeed, X. laevis [frog], G. domesticus [chicken], and M. musculus [mouse] are radically different in such fundamental properties as egg size, fertilization mechanisms, cleavage patterns, and morphogenetic movements. This presents us with a conundrum: If early embryogenesis is conservative, how did such major changes in the earliest events of embryogenesis occur? (Elinson 1987, 3) In fact, the most obvious structural characteristics of either the eggs or the cleavage stages of a shark, a salmon, a frog, a bird, or a mammal are unique each to its own class, not generally shared. We would not consider them very much alike unless we had been taught so at a very early age. ... Each class of vertebrates (in mammals we might almost say each particular order) develops and then loses its own set of temporary structures -- like the parade ground "formations of maneuver" -- during this period. The plain fact is that evolutionary divergence has taken place at every stage in the life history, the earliest no less than the latest. (Ballard 1976, 36) Empirically speaking these embryologists are not even in hailing distance of Ayala. Nor is this unusual. The status of the evolutionary interpretation of von Baer's laws of embryonic similarity [*] (the received view; see Haave and Ayala, above) remains unresolved more than a century after the embryologist Adam Sedgwick (1894, 38) urged that the interpretation "falls to the ground." Interesting raw material, I would say, for philosophers of biology. Gould (1977, 59), for instance, writes of "von Baer's triumph," claiming that "his laws, in refurbished evolutionary dress, are now more widely accepted than ever before." Peter Medawar (1983, 50) argues that the laws (which he thinks are true) were important to the general acceptance of descent: There *is* an element of truth in the so-called law of recapitulation, and it's embodied in Von Baer's law. This affirms that the embryos and young of related animals resemble each other more closely than the adults into which they develop. ... Similarities between mammalian embryos generally and fish embryos in such things as the possession of yolk membranes by the human egg were thought by Thomas Hunt Morgan, and also Thomas Henry Huxley, to be evidence sufficient in itself to justify the acceptance of the evolutionary hypothesis. Properly restated, Lovtrup (1987, 378) argues, von Baer's laws are not only true, but are "the most parsimonious generalisation ever stated in biology." Others, including nearly any developmental biologist who looks at more than his own model system, are unpersuaded. "We see the reality of von Baerian recapitulation," Wake and Roth (1989, 363) demur, "as an open research question." Michael Ghiselin (1988, 84) is less politic. "Von Baer's (1828) laws, which are false," he writes, "were replaced by historical formulae of equally dubious status." Lewis Wolpert (1990, 120) waves von Baer aside, stating that, of the laws, "both the first and third are just wrong: general characters, as we have seen, do not, in early development, necessarily appear before special characters, and neither does an animal depart more and more, during development from the form of other animals." Reviewing what Lovtrup (1987, 378) calls "von Baer's theorem" -- "during their ontogenies the members of twin taxa follow the same course up to the stage where they diverge into separate taxa" -- note the agreement with Ayala's argument above -- Dohle (1988, 285) complains: Everybody who is even slightly acquainted with ontogenetic facts knows that there are hundreds of examples to which this theorem does not apply. In many polychaete and prosobranch genera one species develops through a planktonic larva, whereas another species has direct development. The telolecithal cephalopod eggs cleave in a bilateral manner without any similarity to the spiral cleavage of other related Mollusca. Triclad eggs have a blastomeric anarchy, whereas the adults very closely resemble the polyclads which show spiral cleavage. This list could easily be elongated. This uncertainty pales, however, next to the effect the flood of molecular (homeoprotein) data is having on the standard neo-Darwinian conception of homology. [See, e.g., Panganiban et al. in the latest _PNAS_, 94:5162-66.] But that's a subject for another post. Paul Nelson University of Chicago *As stated by von Baer, these are: a. The general features of a large group of animals appear earlier in the embryo than the special features. b. Less general characters are developed from the most general, and so forth, until finally the most specialized appear. c. Each embryo of a given species [literally <Thierform>], instead of passing through the stages of other animals, departs more and more from them. d. Fundamentally, therefore, the embryo of a higher animal is never like [the adult of] a lower animal, but only like its embryo. (From _Entwicklungsgeschichte der Thiere_ [Borntrager, Konigsberg, 1828], 224; trans. S.J. Gould, _Ontogeny and Phylogeny_ [Cambridge, Mass: Harvard University Press, 1977], p. 56.) Ayala, Francisco. 1988. The Theory of Evolution, _Encyclopedia Britannica_ 15th ed., Vol. 18, p. 987. Ballard, William. 1976. Problems of Gastrulation: Real and Verbal. _BioScience_ 26: 36-39. Dohle, Wolfgang. 1988. Review of Darwinism: The Refutation of a Myth, by Soren Lovtrup. _Journal of Evolutionary Biology_ 1: 283-85. Elinson, Richard P. 1987. Change in Developmental Patterns: Embryos of Amphibians with Large Eggs. In _Development as an Evolutionary Process_, eds. R.A. Raff and E.C. Raff. New York: Alan R. Liss, 1987. Ghiselin, Michael. 1988. The origin of molluscs in the light of molecular evidence. _Oxford Surveys in Evolutionary Biology_, Vol. 5, eds. P. Harvey and L. Partridge (Oxford: Oxford University Press, 1988). Gould, S.J. 1977. _Ontogeny and Phylogeny_ Cambridge, Mass.: Harvard University Press. Lovtrup, Soren. _Darwinism, the Refutation of a Myth_. London: Croom Helm, 1987). Medawar, Peter. 1983. The Evidences of Evolution. In _Darwin's Legacy_, ed. C.L. Hamrum. San Francisco: Harper & Row, 1983, Nobel Conference XVIII. Raff, Rudolf. 1996. _The Shape of Life_. Chicago: University of Chicago Press. Sedgwick, Adam. 1894. On the Law of Development commonly known as von Baer's Law; and on the Significance of Ancestral Rudiments in Embryonic Development. _Quarterly Journal of Microscopial Science_ 36 ([New Series] 1894): 35-52. Wake, David and Roth, Gerhard. 1989. The Linkage between Ontogeny and Phylogeny. In _Complex Organismal Functions_, eds. D.B. Wake and G. Roth. New York: John Wiley, 1989. Wolpert, Lewis. 1990. The evolution of development. _Biological Journal of the Linnean Society_ 39 (1990): 109-124. _______________________________________________________________________________ <45:16>From firstname.lastname@example.org Sat May 24 15:11:56 1997 Date: Sat, 24 May 1997 13:11:49 -0700 From: email@example.com Subject: Re: Ontogeny recapitulates... To: firstname.lastname@example.org, email@example.com Phillip Johnson wrote: >>The "law of recapitulation" has been discredited since the beginning of >>the twentieth century. Experimental morphologists and biologists have >>shown that there is not a one-to-one correspondence between phylogeny >>and ontogeny. Although a strong form of recapitulation is not correct, >>phylogeny and ontogeny are intertwined, and many biologists are beginning >>to both explore and understand the basis for this connection. > >That last sentence is pretty murky, but the public may reasonably take it to >mean that a "weak" form of recapitulation is gaining ground among >biologists, and so "there really is something to it after all." I recently read a similar kind of statement, in Peter Bowler's "Life Splendid Drama"(1996., U.of Chicago Press), p. 83. (the last paragraph of an excellent sub-chapter on the fate of recapitulation law, pp.74-83.): "...In recent years, however, molecular biologists have begun to suspect that genetic mechanisms might sometimes be additive in a way that allows the manifestation of phylogenetically ancient characters before recent ones in ontogeny." Can somebody explain? Bora Zivkovic Department of Zoology North Carolina State University Raleigh, NC _______________________________________________________________________________ <45:17>From firstname.lastname@example.org Sun May 25 10:16:58 1997 Date: Sun, 25 May 1997 11:09:13 -0400 From: email@example.com To: firstname.lastname@example.org Subject: Re: Ontogeny recapitulates... It is very interesting that discussions of the relationship between embryology and evolution, especially among the generally educated public, resolves to Haeckel instead of the other Ernie: i.e., von Baer. How does Haeckel deal with the lack of detailed anatomical correspondence between a specific embyo and a specific adult of the proposed ancestor? This seems to me to be the greatest weakness of Haeckel, one has to do a great deal of filling in and of imagining structures that are not there. Is there anyone who really believes that a fish can be recognized in any stage of human development? spencer turkel nyit email@example.com 516 686 7622 _______________________________________________________________________________ <45:18>From firstname.lastname@example.org Mon May 26 04:53:00 1997 Date: Mon, 26 May 1997 11:52:54 +0200 To: email@example.com From: Michael Schmitt <firstname.lastname@example.org> Subject: Re: Ontogeny recapitulates... At 11:28 23.05.1997 +0000, you wrote: >> Tzvi Langermann >> email@example.com >> >> I would be very interested to learn about the current standing of Ernst >> Haeckel's dictum, "Ontogeny recapitulates phylogeny." >> More specifically, then, I would like to know (1)how the rule is judged >> today--true, false, useful, irrelevant, etc., and (2)the basis for this >> judgment--a consensus of scientists, particular experimental or >> observational evidence, or something else. Whoever is able (and willing) to read German may profit from reading the proceedings of the 24th Phylogenetic Symposium held at Freiburg im Breisgau in 1979 on RECAPITULATION, published in Verhandlungen des naturwissenschaftlichen Vereins Hamburg NF vol. 25, especially Guenther Osche=B4s contribution *Rekapitulationsentwicklungen und ihre Bedeutung fuer die Phylogenetik - wann gilt die Biogenetische Grundregel?* (pp. 5-31). Osche makes the crucial point that, of course, no living organism develops entirely through a stage that resembles another but adult living organism in every respect. Instead, he distinguishes transitional characters in ontogenetic development (interphaen in his terminology) from definitive characters of adults (metaphaen - obviously, these terms were coined by Riedl). Only in cases where homology between an interphaen in question to a metaphaen in another taxon can be established it makes sense to accept the hypothesis of recapitulation. So, the basis for the whole procedure is the concept of homology. Greetings! Michael Schmitt **************************************************************** * Dr. Michael Schmitt (Zoologischer Anzeiger) * * Zoologisches Forschungsinstitut und Museum Alexander Koenig * * Adenauerallee 160, D-53113 Bonn, Germany * * Phone/Fax +49 228-9122 286, e-mail: firstname.lastname@example.org * **************************************************************** _______________________________________________________________________________ <45:19>From email@example.com Mon May 26 10:15:25 1997 Date: Mon, 26 May 1997 10:15:22 -0500 (CDT) From: Gregory Mayer <firstname.lastname@example.org> Subject: Re: Ontogeny recapitulates... To: email@example.com On Fri, 23 May 1997, Neil Haave wrote: > From what I understand, the biogenetic law is not accepted as Haeckel > defined it; that is that organisms go through the adult stages of > their evolutionary ancestors during their development (ontogeny). > However, a revision of this is coming into vogue in biology. The revision referred to is von Baer's law, which is not really a revision since von Baer preceded Haeckel by many years. The real revision is that von Baer's law has been recast in evolutionary terms. (Although their dates overlap, von Baer is largely pre-Darwinian.) Although Haeckel's law has not been accepted by evolutionary biologists for several decades, my personal experience is that it continues to be taught in high schools and freshman college biology courses in the US. "Ontogeny recapitulates phylogeny" seems to be too irresistible a catch phrase for those not versed in the subject. Gregory C. Mayer firstname.lastname@example.org _______________________________________________________________________________ <45:20>From email@example.com Mon May 26 08:25:02 1997 Date: Mon, 26 May 97 09:25:26 -0400 To: firstname.lastname@example.org From: "Jeremy C. Ahouse" <email@example.com> Subject: Re: Ontogeny recapitulates... Paul Nelson in "the role of curmudgeon" has done us a service. Embryological divergence early in development followed by similar structures later in embryogenesis (homologies?!) and then diverging adult forms is visualized by Duboule (in Development 1994 - Supplement p135-142) as an hour glass. Shared and reused developmental regulatory genes will put a lot of pressure on classical notions of homology and analogy. Burian (1997) addresses this. This discussion always returns us to the sticky issue of "genes." I just came across a clear-eyed (and introductory) discussion of this problem that I would like to recommend; Robbins (1996). - Jeremy Burian, R. M. (1997) "On conflicts betweeen genetic and developmental viewpoints - and their attempted resolution in molecular biology." in Structures and Norms in Science. M. L. Dalla Chiara et al. eds. Kluwer Academic Publishers: Netherlands. p 243-264. Robbins, R. J. (1996) "Comparative Genomics: A New Integrative Biology," Ch 4 in Integrative Approaches to Molecular Biology. Julio Collado-Vides et al. eds. MIT Press: Cambridge. p 63-90. -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- Jeremy C. Ahouse Biology Department Brandeis University Waltham, MA 02254-9110 ph: (617) 736-4954 fax: (617) 736-2405 email: firstname.lastname@example.org web: http://www.rose.brandeis.edu/users/simister/pages/Ahouse _______________________________________________________________________________ <45:21>From WirtAtmar@aol.com Tue May 27 14:52:27 1997 Date: Tue, 27 May 1997 15:52:15 -0400 (EDT) From: WirtAtmar@aol.com To: email@example.com Subject: Re: Ontogeny recapitulates... Paul Nelson, serving as curmudgeon-pro-tem, lists a number of people who "wrongly" support either the acceptance in full of the idea of recapitulation or a lesser form of the notion, as embodied by Von Baer's law. One of these people is Peter Medawar. Paul writes: > Peter Medawar (1983, 50) argues that the > laws (which he thinks are true) were important to the general acceptance > of descent: > > There *is* an element of truth in the so-called law of > recapitulation, and it's embodied in Von Baer's law. > This affirms that the embryos and young of related > animals resemble each other more closely than the > adults into which they develop. ... All philosophy aside, it is worth noting that it is standard practice in entomology, especially for those insects that undergo complete metamorphosis (most especially for a great number of fly and beetle species) to not bother trying to identify the larvae but rather merely culture the immature animals until they become adults. It's only then that specialized attributes that truly define the species do develop and become readily apparent and can be used as diagnostic characters. Anyone who has ever attempted taxonomic identification on fly or beetle larvae is more than willing to admit to Medawar's "element of truth" to Von Baer's law. In the absence of any other information, if you are presented with an unknown larva, generally the best that can be hoped for is to get it to family -- and sometimes genus -- but almost never species. The animals are simply too much alike as larvae, no matter how easily distinguishable they become as adults. None of this is to say, of course, that Paul presents a misleading picture. Nonetheless, please allow me to assume an equally curmudgeonly stance, but one that more or less depicts the opposite conclusion. Clearly, evolution is an opportunistic process. Modifications to the code that defines a phyletic lineage -- and its read-out -- can occur at any point, in any manner possible. But it's also clear that terminal modifications to a body of code are easier to accomplish, with greater likelihood of both viability and competitiveness, than those that involve processes that have become deeply ingrained into the development of the phyletic lineage. Profoundly evolved dependencies become the problem associated with any evolving informational structure -- and Bill Gates faces exactly the same problems. When you turn on your Windows 95-based PC, the bootup process (which could easily be declared to be an "embryological development" sequence) fairly directly recapitulates the evolutionary history of the PC as a progressive lineage. Windows 95 is constructed as a shell on top of Windows 3.x, which is itself a shell on top of MS-DOS. If you're still running Windows 3.x, you can see this recapitulation directly. It's better hidden in Windows 95, but it's still there. The reason is fairly straightforward. Bill had no choice but to make it so. Most APIs (application program interfaces) that were developed for MS-DOS came to be supported under Windows 1.0, simply because reusing that code was the simplest and easiest (thermodynamically "cheapest") way to rapidly build new code. Indeed, code re-use lies at the heart of the philosophy of the object-oriented programming model -- and the discovery of such a design philosophy as cell-differentiated colonial metamerism by biological evolution predates Bill's use by about half a billion years. However, once the APIs (system subroutines) were made known to the general software development community with Windows 1.0, they became essentially cast in stone, immutable, although the ones and zeros that comprise these routines in the computer are easily modifidied as any other one or zero. The great problem is that the smallest change in any API presents the opportunity to "break" (render inviable) an unknown number of programs that have become functionally dependent upon that API to operate in the manner that it always has in the past. That dependency only grows more intense with time as more programs come to rely on the presence and the constancy of behavior of every subroutine in the system. To a degree, this simple fact contributes to phenomenon of "software bloat", where every release is twice as big as the one prior. In rather stark contrast, adding new functionality ("terminal" modifications) to a system is easy. You are guaranteed of affecting no existing processes. However, modifying existing code is almost certainly guaranteed of rendering something unexpected and unanticipated non-working -- and thus cannot easily be tolerated. Von Baer's laws could be easily recapitulated themselves in a relatively simple experiment by Mr. Gates, if he wished to do so. If he were to take the programmers at his Redmond, Washington campus and separate them into a thousand geographically isolated locations -- and not let them talk to each other (genetically isolated populations) -- and each were given the mandate to improve the current version of Windows 95, I would wholly anticipate that very little modification would occur to the ancient code that rides with every PC now. Rather, what I would expect is that a thousand new "species" of operating systems would appear, each meant to be aggressively more competitive than the next, but each slightly-to-significantly different than all of the others, where almost all of the modifications were achieved through terminal modifications (new code/new functionalities). In this simple manner, the end result of the process would be quite Von Baerian -- and very reminiscent of the "bootup" processes associated with the development of an insect larva into an adult. The mechanism that essentially predestines such a result is the constant pressure to produce high reliability (high viability) solutions that are aggressively competitive at every point in time throughout the lineage's history. Deep root mutations greatly lessen the probability that such a modification to code can easily exist (or persist). Terminal mutations, on the other hand, don't carry such an extreme penalty. Wirt Atmar The Center for Evolutionary & Environmental Biology The Field Museum of Natural History, Chicago firstname.lastname@example.org _______________________________________________________________________________ <45:22>From email@example.com Tue May 27 15:09:11 1997 Date: Tue, 27 May 1997 16:11:56 -0400 (EDT) From: William Montgomery <firstname.lastname@example.org> To: email@example.com Subject: Re: Ontogeny recapitulates... It is perhaps useful to note that Ernst Haeckel's formulation of the "biogenetic law" (ontogeny recapulates phylogeny) was rather ambiguous. He frequently applied the law to cases in which it appears that he was talking about the recapitulation of adult ancestor forms in the ontogeny of modern embryos. However, he does not seem to have rigorously defined the law in that way. Furthermore, he maintained that his own formulation amounted to little more than the extension of Baer's theory of development to evolutionary cases. Baer, of course, did not see it that way and insisted that Haeckel's notion of the recapitulation of more primitive adult forms was more akin to Meckel's idea, which he (Baer) had explicitly rejected. The business is not easy to sort out. Haeckel clearly did not intend to endorse Meckel's formulation, which did not refer to evolutionary ancestors but simply to more primitive forms in the modern environment. Haeckel described recapitulation as a consequences of additional stages added to the developmental processes of an ancestral form. By itself, this would imply that the ancestral adult form would be incorporated into the developmental stages of some modern from. However, he also explained that natural selection could remove stages from the process, suggesting that the adult ancestral form might not necessarily appear. This made sense from the perspective of a selectionist, but it made it tough to test the proposition empirically. It is worth noting that in Haeckel's day, biologists had only a limited knowledge of the developmental forms for most species. In his monogarph on medusae, Haeckel was unable to describe the life cycle for many of the families he included. He assumed that the polyp form was the original ancestral form (i.e. an adult that has now been superceeded by the evolutionary addition of the medusa), but he was confronted by medusae that reproduced directly without passing through a polyp stage. He concluded that the earlier form had been removed as an evolutionary adaptation, a "just so" story that probably left a lot of biologists unconvinced. Bill Montgomery firstname.lastname@example.org _______________________________________________________________________________ Darwin-L Message Log 45: 11-22 -- May 1997 End
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