The Talk.Origins Archive Post of the Month: February 1999

Subject:    Re: Behe visits Columbia
Newsgroups: talk.origins
Date:       February 7, 1999
Message-ID: 79k6hv$tkv$1@nnrp1.dejanews.com

In article <79f1mb$7ts$1@pale-rider.INS.CWRU.Edu>, iz028@cleveland.Freenet.Edu (Julie Thomas) wrote:
>
> In a previous article, matts2@ix.netcom.com (Matt Silberstein) says:
>
> >In talk.origins I read this message from nyikos@math.sc.edu:
> >
> >>In article <grovesa-0402990952120001@131.215.121.119>,
> >> grovesa@spam-me-not.cco.caltech.edu (Andy Groves) wrote:
> >>> In article <799o7n$f6t$1@nnrp1.dejanews.com>, nyikos@math.sc.edu wrote:
> >>>
> >>> > Behe also showed a transparency from the journal
> >>> > Molecular Biology of the Cell, by Bruce Alberts and
> >>> > James Watson--NAS President and Nobel Laureate, respectively,
> >>> > in which they repeated uncritically Haeckel's claims about
> >>> > the embryos. This was in 1994, hardly a hundred years ago.
> >>>
> >>> Well, in my 1994 edition of Alberts the figure is there all right, but
> >>> no mention of ontogeny recapitulating phylogeny.
> >>
> >>Of course not. Not every use made of those fraudulent
> >>drawings of Haeckel's has to do with that little theme.
> >>
> >So which is the claim, that there was fraud over 100 years ago or that
> >there is fraud now?
>
> This whole issue of Haeckel's drawings in the texts (some as
> recent as 1998) and Richardson's article is not, and has never been,
> about "ontogeny recapitulates phylogeny." The issue has always
> been about whether these embryos are indeed as similar as portrayed
> by Haeckel and in many texts.

I admit that I'm not too impressed by the brief treatment of Haeckel's drawing by Alberts et al. (1994) in Molecular Biology of the Cell. They discuss the early similarities of early embryos and write (p. 32-3): "...it takes an expert eye to distinguish, for example, a young chick embryo from a young human embryo (Figure 1-36)". Then you glance up at that drawing of Haeckel's and get a false impression. The main focus of the Alberts et al text is molecular biology not comparative embryology. William Ballard's text Comparative Anatomy and Embryology has an entire chapter devoted exclusively to the anatomy of the pharyngula (aka vertebrate phylotypic stage). Ballard emphasizes similarities in the idealized stage, but does discuss variability (1964, p. 69): "Some of these actual pharyngulas have a tailfin and some do not. Those which are tetrapods have lung buds, the fish pharyngulas lack them. They all have a liver, to mention an organ at random, but the livers of fishes, birds and mammals are interestingly different in detail even at the pharyngula stage. Arteries can be compared easily but there is little uniformity in the veins. Most conspicuously, the circumstances and needs for respiration, nutrition, and excretion at this stage have been met by a good many structures of a temporary nature, aptly referred to as scaffolding tissues, which are in bold contrast in the different classes of vertebrates."

Ballard's text came out in 1964. His drawings are cartoonish, but there is quite a bit more variability implied than in Haeckel's drawings that you see in the Alberts et al 1994 text. I've seen some questionable allusions to the biogenetic law though, so your point of bringing this drawing up is well taken. Muller (1997, p. 124-5) discusses Haeckel's "serious mistakes", such as comparison of descendent embryo stages with ancestral adult stages. Muller discusses the differences in mammalian early development as being at odds with the biogenetic law, then outlines the processes of palingenesis (recapitulation) and cenogenesis (embryonic adaptation). Muller then modifies the biogenetic law, in the context of a conserved body plan by writing: "Therefore, the biogenetic law is valid if it is modified by stating that all vertebrates recapitulate certain embryonic traits of their ancestors--in particular, a common phylotypic stage." I do not find this to be very palatable. Why invoke recapitulation?

Gerhart and Kirschner (1997, p. 607) in Cell, Embryos and Evolution take a brief stop at Haeckel's door in their chapter "Evolution and Evolvability". Their context is "a succession of embedded evolutionary processes". They discuss modifications to Haeckel's law. The "unipolar Haeckel" model involves only terminal addition where the modifications occur at the end of ontogeny. The "bipolar Haeckel" model is not too different than the "developmental hourglass" model diagrammed by Raff (1996, p. 208) with "prephylotypic developmental trajectories" converging on the phylotypic bottleneck, after which occur divergent "von Baerian developmental trajectories". Notice that Raff has placed this model in the context of von Baer's laws of conservation, not Haeckel's law of recapitulation. The "bipolar Haeckel" model of Gerhart and Kirschner shares the variabilty of early and late ontogeny with the "hourglass". Further modification by Gerhart and Kirschner involves a "two-dimensional" Haeckel model allowing modification of any stage, also allowed for by opening up the "developmental hourglass". This is where Gerhart and Kirschner bring extraembryonic membranes into the picture (aka the scaffolding tissues mentioned by Ballard). One last modification is the "three-dimensional Haeckel" model that incorporates "signal pathways" at the molecular level. Why did Gerhart and Kirschner need to invoke Haeckel in this? Why not von Baer? They seem to have modified Haeckel to the point of absurdity.

Mayr (1994) details the history of the biogenetic law from JF Meckel to Ernst Haeckel. He comments that Haeckel had too much experience as an embryologist to have really thought that a "gill arch" stage mammal embryo actually resembled an adult fish. He modifies the concept of recapitulation by introducing the notion of a "somatic program". Mayr in the 1994 paper, seems to be wearing kid gloves when it comes to Haeckel, as opposed to von Baer, who refuted recapitulation in 1828 with his four laws (see Gould, 1977, p. 56).

In his book This is Biology (1997, p. 171) Mayr maintains that recapitulation proponents such as Haeckel were actually proposing that descendent embryos resembled the "permanent", not "adult", stages of ancestors. His treatment of Haeckel aside, Mayr's concept of the "somatic program" could be valuable as it is probably not far removed from the continental Bauplan or epigenetics.

> From the Science article that
> reviewed Richardson's work:
>
> After taking careful photographs of embryos that roughly match the
> species and age used in Haeckel's drawings, Richardson found they
> "often looked surprisingly different."
>
> In order to make the different vertebrate embryos look so similar,
> Haeckel's drawings contain things not seen, omit things that are there,
> fudge the scale even when there is a 10-fold difference in size, and
> create the impression that there are no significant variations within
> groups. Richardson notes, "it looks like it's turning out to be one of the
> most famous fakes in biology."

Haeckel's drawings were wrong and outdated, but does this eliminate the possibility of a conserved phylotypic stage or period altogether? I haven't received the Richardson et al 1997 paper in Anatomy and Embryology yet. Hall (1997) discusses the work of Richardson and colleagues. The big dispute might be over whether phylotypy occurs in a "stage" or a "period". Hall acknowledges the importance of their work but disputes replacement of the term "stage" with "period". Hall describes Ballard's (1976, 1981) pharyngula as a "visceral animal". He argues that Richardson and colleagues focus on embryonic adaptations rather than the defining criteria used by Ballard. Richardson (1998a) has replied to Hall's article arguing that the pharyngula is an archetype (in the morphological idealistic spirit of Richard Owen) and adding that heterochrony obscures the conservation, making it hard to define a stage that is shared. Richardson (1998b) discusses variation in somite number as a "dissociation" that disrupts the neatness of the "developmental hourglass" model.

So I agree that Haeckel's drawings are dated, inaccurate, and inappropriate for use in textbooks, because they help perpetuate a bad idea. Recapitulation (aka the biogenetic law) should probably be put to rest, no matter how elaborately phrased or modified. Conservation of developmental stage, period, or process, on the other hand, is a topic that is open for debate.

Alberts B, Bray D, Lewis J, Raff M, Roberts K, Watson JD. 1994. Molecular Biology of the Cell (3rd edition). Garland Publishing, Inc. New York.

Ballard WW. 1976. Problems of gastrulation: real and verbal. Bioscience (26): 36-9.

Ballard WW. 1981. Morphogenetic movements and fate maps of vertebrates. Amer. Zoo. (21): 391-9.

Ballard WW. 1964. Comparative Anatomy and Embryology. The Ronald Press Company. New York.

Gerhart J and Kirschner M. 1997. Cells, Embryos, and Evolution: Toward a Cellular and Developmental Understanding of Phenotypic Variation and Evolutionary Adaptability. Blackwell Science. Malden, Massachusetts.

Gould SJ. 1977. Ontogeny and Phylogeny. The Belknap Press of Harvard University Press. Cambridge, Massachusetts.

Hall BK. 1997. Phylotypic stage or phantom: is there a highly conserved embryonic stage in vertebrates? Trends in Ecology and Evolution(12): 461-3.

Mayr E. 1997. This is Biology: the Science of the Living World. The Belknap Press of Harvard University Press. Cambridge, Massachusetts.

Mayr E. 1994. Recapitulation reinterpreted: the somatic program. The Quarterly Review of Biology (69): 223-232.

Raff RA. 1996. The Shape of Life: Genes, Development, and the Evolution of Animal Form. The University of Chicago Press, Chicago.

Richardson MK. 1998a. Phylotypic stage theory. Trends in Ecology and Evolution (13): 158.

Richardson MK. 1998b. Somite number and vertebrate evolution. Development (125): 151-160.

Is Haeckel's law of recapitulation a problem?

Post of the Month: February 1999