Good Science Writers: Stephen Jay Gould

 
Stephen Jay Gould is far too good a writer to have been ignored by Richard Dawkins in his book: The Oxford Book of Modern Science Writing. According to Dawkins, he and Gould "... enjoyed—or suffered—a kind of love/hate relationship on opposite sides of the Atlantic and opposite sides of several schisms in the broad church of Darwinian theory."¹ Dawkins selected an essay by Gould on Charles Darwin's book on worms.

I think Gould deserves a better hearing so I've selected two excerpts that show where he differs from Dawkins. The first is from Wonderful Life (1989). Here Gould is discussing the Burgess Shale and notes that there were many diverse species, most of which have not left modern ancestors. If you represent this diversity—or disparity as Gould prefers—as a tree, it has a rapidly expanding bushiness and out of that wide base only a few branches extend upwards to modern times. This is very unlike the traditional tree that looks more like an inverted cone with steadily increasing diversity. Gould draws certain conclusions from this data—conclusions that have been widely misinterpreted. If you're going to engage in the "evolution wars" it's a good idea to get the views of your opponents right.

This inverted iconography, however interesting and radical in itself, need not imply a revised view of evolutionary predictability and direction. We can abandon the cone, and accept the inverted iconography, yet still maintain full allegiance to tradition if we adopt the following interpretation: all but a small percentage of Burgess possibilities succumbed, but the losers were chaff, and predictably doomed. Survivors won for cause—and cause includes a crucial edge in anatomical complexity and competitive ability.

But the Burgess pattern of elimination also suggests a truly radical alternative, precluded by the iconography of the cone. Suppose that winners have not prevailed for cause in the usual sense. Perhaps the grim reaper of anatomical designs is only Lady Luck in disguise. Or perhaps the actual reasons for survival do not support conventional ideas of cause as complexity, improvement, or anything at all humanward. Perhaps the rim reaper works during brief episodes of mass extinction, provoked by unpredictable envirnonmental catastrophes (often triggered by impacts of extraterrestrial bodies). Groups may prevail or die for reasons that bear no relationship to the Darwinian basis of success in normal times. Even if fishes hone their adaptations to peaks of aquatic perfection, they will all die if the ponds dry up. But grubby old Buster the Lungfish, former laughing stock of the piscine priesthood, may pull through—and not because a bunion on his great-grandfather's fin warned his ancestors about a coming comet. Buster and his kin may prevail because a feature evolved a long time ago for a different use has fortuitously permitted survival during a sudden and unpredictable change in rules. And if we are Buster's legacy, and the result of a thousand other similar happy accidents, how can we possible view our mentality as inevitable, or even probable?

We live, as our humorists proclaim, in a world of good news and bad news. The good news is that we can specify an experiment to decide between the conventional and the radical interpretations of extinction, thereby settling the most important question we can ask about the history of life. The bad news is that we can't possibly perform the experiment.

I call this experiment "replaying life's tape." You press the rewind button and, making sure you thoroughly erase everything that actually happened, go back to any time and place the past—say, to the seas of the Burgess Shale. Then let the tape run again and see if the repetition looks at all like the original. If each replay strongly resembles life's actual pathway, then we must conclude that what really happened pretty much had to occur. But suppose that the experimental versions all yield sensible results strikingly different from the actual history of life? What could we then say about the predictability of self-conscious intelligence? or of mammals? or of vertebrates? or of life on land? or simply multicellular persistence for 600 million years? (pp. 48-50)

Note the contrast between Gould's views and those of theistic evolutonists such as Ken Miller and Simon Conway Morris. Those writers emphasize that the replay of the tape of life would still produce intelligent beings with a soul. They claim that the evidence of convergence favors such a view.

The second excerpt comes from The Structure of Evolutonary Theory. Here Gould is discussing the demise of the hardened version of the Modern Synthesis. He claims that this version, entrenched in the 1950's, is no longer correct. It needs to be expanded to include other modes of evolution.

I choose this example to illustrate two things about Gould: first, the reason why he makes such a claim and, second, how he addresses his critics. The necessity of responding to other points of view is exactly what one expects from a scientist but, unfortunately, few scientists exhibit this characteristic.

Gould is referring to an article he published in Paleobiology back in 1980. In that article he quoted Ernst Mayr's definition of the Modern Synthesis² and then pronounced it "effectively dead."

Given the furor provoked, I would probably tone down—but not change in content—the quotation that has come to haunt me in continual miscitation and misunderstanding by critics: "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" (Gould, 1980). (I guess I should have written the blander and more conventional "due for a major reassessment" or "now subject to critical scrutiny and revision," rather than "effectively dead." But, as the great Persian poet said, "the moving finger writes, and having writ ..." and neither my evident piety nor obvious wit can call back the line—nor would tears serve as a good emulsifier for washing out anything I ever wrote!)

Yes, the rhetoric was too strong (if only because I should have anticipated the emotional reaction that would then preclude careful reading of what I actually said). But I will defend the content of the quotation as just and accurate. First of all, I do not claim that the synthetic theory of evolution is wrong, or headed for complete oblivion on the ashheap of history; rather, I contend that the synthesis can no longer assert full sufficiency to explain evolution at all scales (remember that my paper was published in a paleobiological journal dedicated to the studies of macroevolution). Two statements in the quotation should make this limitation clear. First of all, I advanced this opinion only with respect to a particular, but (I thought) quite authoritative, definition of the synthesis: "if Mayr's characterization of the synthetic theory is accurate." Moreover, I had quoted Mayr's definition just two paragraphs earlier. The definition begins Mayr's chapter on "species and transspecific evolution" from his 1963 classic—the definition that paleobiologists would accept as most applicable to their concerns. Mary wrote (as I explicitly quoted): "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."

Second, I talked about the theory being dead "as a general proposition," not dead period. In the full context of my commentary on Mayr's definition, and my qualification about death as a full generality, what is wrong with my statement? I did not proclaim the death of Darwinism, or even of the strictest form of the Modern Synthesis. I stated, for an audience interested in macroevolutionary theory, that Mayr's definition (not the extreme statement of a marginal figure, but an explicit characterization by the world's greatest expert in his most famous book)—with two restrictive claims for (1) "all evolution" due to natural selection of small genetic changes, and (2) transspecific evolution as "nothing but" the extrapolation of microevolutionary events.—must be firmly rejected if macroevolutionary theory merits any independent status, or features any phenomenology requiring causal explanation in its own domain. If we embrace Mayr's definition, then the synthesis is "effectively dead" "as a general proposition"—that is, as a theory capable of providing a full and exclusive explanation of macroevolutionary phenomena. Wouldn't most evolutionary biologists agree with my statement today?

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1. It's interesting that even when describing their differences, Dawkins puts it in the context of "Darwinian theory." Anyone familiar with the conflict knows that it was really about additions to, or conflicts with, strict "Darwinism."

2. Gould discuss this again in his 1980 Science article on "Darwinism and the Expansion of Evolutionary Theory." In that article he quotes Mayr's definition of the Modern Synthesis ...

The term "evolutionary synthesis" was introduced by Julian Huxley ... to designate the general acceptance of two conclusions: gradual evolution can be explained in terms of small genetic changes ("mutations") and recombination, and the ordering of this genetic variation by natural selection: and the observed evolutionary phenomena, particularly macroevolutionary processes and speciation, can be explained in a manner that is consistent with the known genetic mechanisms.

[Image Credit: Photograph of Stephen Jay Gould by Kathy Chapman from Lara Shirvinski at the Art Science Research Laboratory, New York (Wikipedia)]