This is a genuine question, not a rhetorical one.
From the mid-70s up to about 1990, there was controversy about the punctuated equilibrium theory of evolution. You could hardly open a scientific magazine like New Scientist or Scientific American without finding some new argument.
But from 1990 onwards interest in the subject seems to have declined. Am I right about this, or have I just developed a blind spot?
I’m aware that shortly before his death Stephen Jay Gould published a vast book on The Structure of Evolutionary Theory, which I haven’t read, but judging from the reviews it was just a rehash of everything he’d said before. The general lack of excitement at its publication suggests a loss of interest in the controversy.
If I am right about this, what is the explanation? Have biologists reached a consensus on the merits of the case? Or have they just got bored with it?
I have no strong view on the issue myself. What I found annoying about Eldredge and Gould’s approach is the way they exaggerated the novelty of their theory. In particular their treatment of George Gaylord Simpson was outrageous. Their own theory could well have been presented as an extension of Simpson’s idea of quantum evolution, but instead they chose either to ignore him or to mention only their disagreements with him. Of course, the controversy also got entangled with Gould’s crusade against adaptationism, and his flirtation with macromutation.
But on the substance of the issues, I think there is quite a lot to be said for punctuated equilibrium. I could even live with a bit of macromutation if necessary.
Ultimately the prevalence of a punctuational mode of evolution is an empirical matter. The controversy dragged on for so long because the fossil record is seldom good enough to trace in detail the transition from one species to another.
But it strikes me that the controversy took place in the era before DNA sequencing. Surely the new technology should transform the terms of the debate? By comparing the genes of closely related species, isn’t it possible in principle to reconstruct the course and timing of the genetic divergence between them? On a broader scale one could do the same with genera, families, etc.
Maybe a lot of work like this is going on, but if so I don’t think it has yet filtered through to the general scientific public. There has been a good deal of work aimed at resolving disputes in phylogeny (like the relationships of the various invertebrate phyla), but this is not quite the same issue. What I have in mind are questions like: how long did it take for (e.g.) lions to diverge from leopards and tigers? How many gene substitutions were involved? Were they genes with major phenotypic effects, or were there a large number of small changes? Is it possible to estimate the size of the populations during the transition? Were the changes concentrated in the period when the species became reproductively isolated from each other, or were they spread out over a longer period?
As always, I hope someone can point me to relevant work that I wasn’t aware of.
DAVID BURBRIDGE
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