Punctuated equilibrium

[haggholm]

Perhaps influenced by Richard Dawkins, I find the concept of punctuated equilibrium in evolutionary biology to be irritatingly overhyped. Without going into extremely technical details, I will cite Wikipedia—very deliberately: Regardless of technicalities, this is the popular perception of the idea. Emphasised text highlights the P.E.-ists’ understanding of classic Darwinian theory.

Punctuated equilibrium is a theory of evolutionary biology which states that most sexually reproducing populations experience little change for most of their geological history, and that when phenotypic evolution does occur, it is localized in rare, rapid events of branching speciation (called cladogenesis).

Punctuated equilibrium is commonly contrasted against the theory of phyletic gradualism, which states that evolution generally occurs uniformly and by the steady and gradual transformation of whole lineages (anagenesis). In this view, evolution is seen as generally smooth and continuous.

In 1972 paleontologists Niles Eldredge and Stephen Jay Gould published a landmark paper developing this idea. Their paper was built upon Ernst Mayr's theory of geographic speciation, I. Michael Lerner's theories of developmental and genetic homeostasis, as well as their own empirical research. Eldredge and Gould proposed that the degree of gradualism championed by Charles Darwin was virtually nonexistent in the fossil record, and that stasis dominates the history of most fossil species.

Compare this to the following, where emphasised text marks Darwin’s understanding of his theory.

…I must here remark that I do not suppose that the process ever goes on so regularly as it is represented in the diagram, though in itself made somewhat irregular, nor that it goes on continuously; it is far more probable that each form remains for long periods unaltered, and then again undergoes modification. Nor do I suppose that the most divergent varieties are invariably preserved: a medium form may often long endure, and may or may not produce more than one modified descendant…

Charles Darwin, On the Origin of Species

I don’t know which edition of the Origin my copy reproduces. The first edition was published in 1859; the sixth (and final) edition that Darwin produced was published in 1872. By the most generous estimate, then, it seems to me that Darwin came up with a version of the idea a century before Gould and Eldredge—which makes the notion of punctuated equilibrium being a novel, revolutionary, or landmark idea seem fairly ridiculous. It may be—in fact, almost certainly is—correct, but doesn’t deserve the press it has received, and it’s Darwin, not Gould, who should get the credit.