Posted by Richard B. Hoppe on May 30, 2004 04:13 PM

In response to postings on The Panda’s Thumb criticizing the IDEA Club’s description of punctuated equilibirum, Casey Luskin invited corrections.  I have one or two suggestions.  This is not exhaustive; I treat just one aspect of the FAQ.

The IDEA Club description first sets the problem by describing what it represents to be the ‘orthodox’ view of evolution, quoting Gould

Is long, slow, “gradual” evolution (see Figure 1) an inference from the evidence, or was it assumed simply because of naturalism and what was predicted by Darwin’s theory? Gould explains it is inference:

“The extreme rarity of transitional forms in the fossil record persists as the trade secret of paleontology. The evolutionary trees that adorn our textbooks have data only at the tips and nodes of their branches; the rest is inference, however reasonable, not the evidence of fossils.”

(Internal quotation referenced to Gould, S. J., “Evolution’s erratic pace,” Natural History, Vol. 86, No. 5, pp.12-16, (May 1977; Emphasis added by Luskin, the author of the description)

The IDEA Club Figure gets Darwin’s view of the ‘tree of life’ wrong.  In OoS there is just this one illustration, on page 90, which shows Darwin’s conception of a segment (one genus) of the structure of the tree of life, and the IDEA Club Figure misrepresents it.  Describing the illustration, Darwin wrote

The accompanying diagram will aid us in understanding this rather perplexing subject. Let A to L represent the species of a genus large in its own country; these species are supposed to resemble each other in unequal degrees, as is so generally the case in nature, and as is represented in the diagram by the letters standing at unequal distances. … The variations are supposed to be extremely slight, but of the most diversified nature; they are not supposed all to appear simultaneously, but often after long intervals of time; nor are they all supposed to endure for equal periods.

[…]

But I must here remark that I do not suppose that the process ever goes on so regularly as 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; for natural selection will always act according to the nature of the places which are either unoccupied or not perfectly occupied by other beings; and this will depend on infinitely complex relations. But as a general rule, the more diversified in structure the descendants from any one species can be rendered, the more places they will be enabled to seize on, and the more their modified progeny will increase. In our diagram the line of succession is broken at regular intervals by small numbered letters marking the successive forms which have become sufficiently distinct to be recorded as varieties. But these breaks are imaginary, and might have been inserted anywhere, after intervals long enough to allow the accumulation of a considerable amount of divergent variation.  (pp 90-91, emphasis added)

Nowhere does Darwin succumb to the simplistic notion that evolution proceeds at a slow, gradual, constant rate; he explicitly and repeatedly mentions variation in rates of change.  His repeated use of “gradual” and “slow” must be understood in historical context.  An important competitor to his view of evolution as the incremental accumulation of favorable variations due to natural selection was saltationism.  Even Darwin’s bulldog, Thomas Huxley, believed that large sudden changes from one generation to another were necessary to account for at least some biological change.  Darwin firmly resisted saltationism — witness his famous assertion Nature non facit saltum — and he emphasized the incremental nature of evolution in opposition.  (See Edward J. Larson, Evolution: The Remarkable History of a Scientific Theory, The Modern Library, 2004, pp. 86-87.)  In every case I have found where Darwin uses “gradual” in OoS one could substitute “incremental” with no change in Darwin’s meaning.

Finally, the IDEA Club description has a short section entitled “Is Punctuated Equilibrium a Scientific Theory?”  In that section Luskin makes a ludicrous assertion:

But what hard evidence does punctuated equilibrium predict? Macroevolution by punctuated equilibrium predicts that transitional forms will not be found. With respect to finding fossil evidence of the stages of evolutionary change, punctuated equilibrium predicts that evidence of these changes will not be found. (Emphasis added)

That’s complete glop.  Punctuated equilibrum makes a very specific prediction about the kind of corroborating evidence it expects, and as Wes Elsberry pointed out (May 27, 2004 01:36 PM posting),

The FAQ claims that PE predicts that no data will be found to support it, yet Eldredge and Gould presented two transitional sequences supporting transitions via PE in their original essay, and cited further examples in their 1977 paper.

I look forward to corrections in the IDEA Club’s Punctuated Equilibrium FAQ.

RBH

Edited 6/1/04 to remove an incorrect reference to extinction.