Evolution: The Pleasures of Pluralism

Charles Darwin began the last paragraph of The Origin of Species (1859) with a famous metaphor about life’s diversity and ecological complexity:

It is interesting to contemplate an entangled bank, clothed with many plants of many kinds, with birds singing on the bushes, with various insects flitting about, and with worms crawling through the damp earth, and to reflect that these elaborately constructed forms, so different from each other, and dependent on each other in so complex a manner, have all been produced by laws acting around us.

He then begins the final sentence of the book with an equally famous statement: “There is grandeur in this view of life….”

For Darwin, as for any scientist, a kind of ultimate satisfaction (Darwin’s “grandeur”) must reside in the prospect that so much variety and complexity might be generated from natural regularities—the “laws acting around us”—accessible to our intellect and empirical probing. But what is the proper relationship between underlying laws and explicit results? The “fundamentalists” among evolutionary theorists revel in the belief that one overarching law—Darwin’s central principle of natural selection—can render the full complexity of outcomes (by working in conjunction with auxiliary principles, like sexual reproduction, that enhance its rate and power).

The “pluralists,” on the other hand—a long line of thinkers including Darwin himself, however ironic this may seem since the fundamentalists use the cloak of his name for their distortion of his position—accept natural selection as a paramount principle (truly primus inter pares), but then argue that a set of additional laws, as well as a large role for history’s unpredictable contingencies, must also be invoked to explain the basic patterns and regularities of the evolutionary pathways of life. Both sides locate the “grandeur” of “this view of life” in the explanation of complex and particular outcomes by general principles, but ultra-Darwinian fundamentalists pursue one true way, while pluralists seek to identify a set of interacting explanatory modes, all fully intelligible, although not reducible to a single grand principle like natural selection.

The first part of this article outlined the general fallacies of ultra-Darwinian fundamentalism, especially in the light of new theories and discoveries in the core disciplines of developmental biology, paleontology, and population genetics. In this second and concluding part, I shall analyze a prominent philosopher’s influential but misguided ultra-Darwinian manifesto—Darwin’s Dangerous Idea, by Daniel Dennett. I shall also take upthe meth-odology of so-called “evolutionary psychology”—a field now in vogue as a marketplace for ultra-Darwinian explanatory doctrine. Evolutionary psychology could, in my view, become a fruitful science by replacing its current penchant for narrow, and often barren, speculation with respect for the pluralistic range of available alternatives that are just as evolutionary in status, more probable in actual occurrence, and not limited to the blinkered view that evolutionary explanations must identify adaptations produced by natural selection.

Daniel Dennett devotes the longest chapter in Darwin’s Dangerous Idea to an excoriating caricature of …

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Letters

Darwinian Fundamentalism’: An Exchange August 14, 1997