Stephen Jay Gould

It was on this day, September 10, in 1941 that Stephen Jay Gould was born.

Gould was both a paleontologist and a popularizer of science, who died of lung cancer in May 2002.

Above all, IMHO, Gould was a fine writer, and he had the good fortune of leaving a Magnum Opus behind -- The Structure of Evolutionary Theory (2002)-- its publication date preceding his death by only two months.

In this work, Gould described evolutionary theory as a tripod. One leg is the agency of the individual organism. The second leg is the efficacy of natural selection in bringing about changes in form. The final leg is the full sufficiency of the first two legs, as a mode of explanation.

That third leg, Gould calls "scope." For critics of Darwin often make some concession to the effect that his theory has some value, but only if its scope is confined to "microevolution." Darwin's view, and Gould's, was that "extended through the immensity of geological time," natural selection and the agency of individuals make up a mechanism "fully capable of generating the entire pageant of life's history."

What is that "agency of the individual" thing, though? It is only worth listing this as a "leg" if there are other possible units of selection that might do some or all of the work. For example, Dawkins looks inside the individual, and speaks of individual genes are agents. The whole biological organism is too large a proposed "agent" on that view. Another point of view might be that the individual is too small an entity -- one ought to think of flocks or herds, social units, as the relevant agent.

Finally, let us note that Gould himself had a fairly complicated attitude toward both of those proposed agents -- the social unit and the gene. But as a historian of science, insisting on what Darwin thought, Gould wrote this: "Darwin insisted upon a virtually exceptionless, single-level theory, with organisms acting as the locus of selection."