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)
This is illustrated by Figure 1. No source is given for Figure 1, so I assume that it is the construction of Luskin, the author of the description.
Language in the description attributes the gently sloping ascents of the lines in Figure 1 to Darwin, using phrases like “Darwin’s predicted slow and gradual evolution” and “Darwin saved his gradual theory of evolution by claiming …”. But Darwin was not, to use Dawkins’ felicitous phrase, a “constant speedist.” In OoS (6th Edition), Darwin wrote:
These several facts accord well with our theory, which includes no fixed law of development, causing all the inhabitants of an area to change abruptly, or simultaneously, or to an equal degree. The process of modification must be slow, and will generally affect only a few species at the same time; for the variability of each species is independent of that of all others. Whether such variations or individual differences as may arise will be accumulated through natural selection in a greater or less degree, thus causing a greater or less amount of permanent modification, will depend on many complex contingencies–on the variations being of a beneficial nature, on the freedom of intercrossing, on the slowly changing physical conditions of the country, on the immigration of new colonists, and on the nature of the other inhabitants with which the varying species come into competition. Hence it is by no means surprising that one species should retain the same identical form much longer than others; or, if changing, should change in a less degree. We find similar relations between the existing inhabitants of distinct countries; for instance, the land-shells and coleopterous insects of Madeira have come to differ considerably from their nearest allies on the continent of Europe, whereas the marine shells and birds have remained unaltered. (p. 291)
There are several references to rates and amounts of change in that one paragraph. Most important is the “no fixed law of development” phrase. While Darwin certainly held evolution to be gradual, in the sense of incremental, he did not hold that evolution proceeded at a constant rate, and in fact discussed some variables he thought would affect evolutionary rates of change.
Compare the IDEA Club figure above with the illustration in OoS:
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.
Edited 6/1/04 to remove an incorrect reference to extinction.