There seems to be new interest in the blogosphere regarding what Stephen Jay Gould had to say about evolution, invigorated, at least in part, by Jerry Coyne’s post on The Loom. This appears to have grown into the creation of a “ScienceBlogs Book Club” which will discuss Gould’s massive book, The Structure of Evolutionary Theory. I read it when it came out. I am certain that Larry Moran has read it. But we’re not on ScienceBlogs (he declined, and I was never approached). I also am fairly sure that PZ Myers has read it, so maybe he can provide some perspective.

My last post dealt briefly with one aspect of this discussion, namely a misinterpretation of punctuated equilibria as representing a saltatationist mechanism. In no small part, this has been based on cherry picking quotes from Gould’s diverse writings, which did indeed cover mutations of substantial effect in addition to patterns of speciation in geological timescales.

This time I want to revisit one of Gould’s most famous quotes, and certainly his most infamous. The version that is most familiar, I believe, is the one cited in Charlesworth et al. (1982), who quote Gould thus:

I have been watching it [neo-Darwinism] slowly unravel as a universal description of evolution … I have been reluctant to admit it … but … that theory, as a general proposition, is effectively dead, despite its persistence as a text-book orthodoxy.

Strong claims, to be sure. But evolutionary biologists, I should hope, are always wary of ellipses, and that passage has several.

Here is Gould’s (1980) quote in full (emphasis added):

I well remember how the synthetic theory beguiled me with its unifying power when I was a graduate student in the mid-1960’s. Since then I have been watching it slowly unravel as a universal description of evolution. The molecular assault came first, followed quickly by renewed attention to unorthodox theories of speciation and by challenges at the level of macroevolution itself. I have been reluctant to admit it — since beguiling is often forever — but if Mayr’s characterization of the synthetic theory is accurate, then that theory, as a general proposition, is effectively dead, despite its persistence as textbook orthodoxy.

The question is, what was Mayr’s characterization that Gould considered effectively dead as a general proposition?

Ernst Mayr (1963) (emphasis added):

The proponents of the synthetic theory maintain that all evolution is due to the accumulation of small genetic changes, guided by natural selection, and that transspecific evolution is nothing but an extrapolation and magnification of the events that take place within populations and species.

Polyploidy. Genetic drift. Mass extinction. Gould said many controversial things, but his claim, without ellipses, that the modern synthesis so defined had perished was pretty neutral.

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References

Charlesworth, B., R. Lande, and M. Slatkin. 1982. A neo-Darwinian commentary on macroevolution. Evolution 36: 474-498.

Gould, S.J. 1980. Is a new and general theory of evolution emerging? Paleobiology 6: 119-130.

Mayr, E. 1963. Animal Species and Evolution. Harvard University Press, Cambridge, MA.

If I get more time, I may weigh in on the debate that has erupted of late on several blogs, namely regarding saltationism in evolution. This was sparked by Olivia Judson’s post, and fanned by Jerry Coyne’s guest critique on Carl Zimmer’s blog, The Loom.

For the moment, I will sidestep the issue of small mutations of large effect (and the additional issue of large mutations, like genome duplications) and will focus briefly on the claim that Coyne makes in the post and in various articles that Eldredge and Gould’s idea of punctuated equilibria is, or at least was, saltationist in mechanism.

It isn’t. It never was. Gould did maintain an interest in macromutations in his discussion of development in the 1970s and 80s, but this was separate from punk eek. Linking them just because the same author discussed them would be like calling natural selection a Lamarckian theory because Darwin considered the inheritance of acquired characteristics in the Origin.

I am pleased to note that Niles Eldredge will provide an article entitled “The early evolution of punctuated equilibria” as his Editor’s Corner of the forthcoming issue of Evolution: Education and Outreach, so look for that in the spring and for additional discussions in future issues of the journal.

You can also consult Gould’s The Structure of Evolutionary Theory, or the chapter on the topic that was published alone as Punctuated Equilibrium.

Meanwhile, I will simply direct you to the summary of punctuated equilbria by Bruce Lieberman and Niles Eldredge at Scholarpedia:

Punctuated equilibria actually comprises several different and related observations. These include:

1. the fossil record contains a rich source of data useful for developing important evolutionary hypotheses;
2. speciation typically happens allopatrically, in narrow and geographically restricted populations containing relatively few individuals;
3. species are not slowly and gradually adapting and evolving over long stretches of geological time;
4. species lineages that show stasis – or an absence of morphological change – dominate the fossil record and provide useful information about the tempo and mode of evolution;
5. the first appearance of a new species in the fossil record usually does not represent its point of evolutionary origin but rather the migration of a new geographically isolated species back into its ancestral range, with concomitant expansion in abundance; and
6. speciation typically takes on the order of 5,000 to 50,000 years to occur – far shorter than the average duration of species in the fossil record.

This is, in essence, an extrapolation into deep evolutionary time, of Ernst Mayr’s ideas regarding allopatric speciation. Mayr himself thought so:

I believe I was the first author to develop a detailed model of the connection between speciation, evolutionary rates, and macroevolution (Mayr, 1954). Although long ignored, my new theory of the importance of peripatric speciation in macroevolution is now widely recognized. “Mayr’s hypothesis of peripheral isolates and genetic revolution must of necessity be a centerpiece of the punctuated equilibria theory; it is the theory, for all practical purposes” (Levinton, 1983:113). I once more presented my theory in great detail (Mayr, 1963:527-555). Under these circumstances it is most curious that the theory was completely ignored by paleontologists until brought to light by Eldredge and Gould (1972).

Mayr, E. 1992. Speciational evolution or punctuated equilibria. In: The Dynamics of Evolution (eds. A. Somit and S.A. Peterson), pp. 21-53. Cornell University Press, Ithaca, NY.

Indeed, here is what he said in the 1954 paper:

…rapidly evolving peripherally isolated populations may be the place of origin of many evolutionary novelties. Their isolation and comparatively small size may explain phenomena of rapid evolution and lack of documentation in the fossil record, hitherto puzzling to the palaeontologist.

Mayr, E. 1954. Change of genetic environment and evolution. In: Evolution as a Process (eds. J.S. Huxley A.C. Hardy, and E.B. Ford), pp. 157-180. George Allen & Unwin, London.

Several bloggers have discussed Coyne’s critique, and you can find summaries here and here. The one to which I most enthusiastically direct you is by Larry Moran. Larry puts it clearly, and points out that even one of Gould’s major detractors agreed that Gould never proposed punctuated equilibria as a saltationist process. Incidentally, I am not the only person to endorse that post. As Niles Eldredge told me when I mentioned the blog discussions, “PS: Larry Moran says it all!”.