CAN PUNCTUATED EQUILIBRIUM EXPLAIN THE CAMBRIAN EXPLOSION?
Punctuated equilibrium predicts the biological change we see over millions of years will occur in large jumps as a result of natural selection. It focuses on the species as a whole. Whereas Darwinian evolution predicts slow change over time, punctuated equilibrium proposes massive changes acting upon the species. The theory actually came about because of what the fossil record reveals. In the geological strata under the ocean scientists, like Stephen Gould and Niles Eldridge, found fully formed creatures with little to no precursors. These findings needed an explanation, hence punctuated equilibrium. However, this theory still needs transitional forms.
Punctuated equilibrium suffers from the same fossil problem as Neo-Darwinian evolution. Both are missing transitional forms in the fossil record. Plus punctuated equilibrium is in need of a mechanism to account for organisms making sudden jumps of complexity to produce macro-evolutionary change. Neither Michael Foote nor Stephen J. Gould nor anyone else has identified such a mechanism with any genetic or developmental plausibility.
The first premise needed to demonstrate the truth of the theory, was the fossil record would reveal a movement from simple to complex. The Cambrian fossil record failed to show this and lacked multiple transitional forms leading to new phylum-level body plans. For this reason the first premise of both theories suffer from the absence of needed evidence.
The second premise was that we should see small-scale morphological diversity coming before large-scale morphological disparity. Diversity describes the small scale variations that correspond to the lower levels of the biological classifications of genus and species. Disparity refers to the major differences in morphology or body structure corresponding to the higher levels of the biological classifications such as phyla and kingdom.
According to both evolutionary theories we should see gradual low level speciation events leading upwards cumulatively and gradually, to novel body plans that define different phyla. Diversity must precede disparity. The fossil record should demonstrate the biological classifications beginning at the lowest level species and working upward through phyla onto kingdom. So what do we see in the fossil record?
We see a contradiction of these predictions in the Cambrian fossil record. The evidence shows a “top-down” pattern in which large-scale morphological disparity precedes diversity. Instead of the gradual step-by-step process moving upward that both Neo-Darwinian evolution and punctuated equilibrium predict (a bottom-up model), we find multiple separate body plans emerging suddenly and prior to any species-level diversification. Erwin, Valentine, and Sepkoski in their study of marine invertebrates wrote:
“Most higher taxa were built from the top down, rather than from the bottom up. The fossil record suggests that the major pulse of diversification of phyla occurs before that of classes, classes before that of orders, orders before that of families. The higher taxa do not seem to have diverged through an accumulation of lower taxa.”
These findings are the complete opposite of what both evolutionary theories would expect. Higher level complex body plans appear first in the fossil record and then later the lower-level taxonomic differences appear, from order, families, genus, and so on. Neither theory shows small-scale morphological diversity coming before large-scale morphological disparity. Thus the second premise is false.
Finally, according to both evolutionary theories we should observe a steady increase in the number of phyla over time (accounting for extinctions along the way). Is this the conclusion of the fossil record?
Instead of discovering a steadily increasing number of phyla over time we see a sudden explosion of phyla first appearing in the Cambrian strata followed by either a few small bursts or as some scientists contend no new phyla appearing after the Cambrian geological time period. When looking at the millions of years before and after the Cambrian, the fossil record does not demonstrate a steadily increasing number of new phyla as Neo-Darwinian evolution and punctuated equilibrium predict. Instead we find a sudden appearance of 19 or more phyla followed by stasis; opposite of both evolutionary predictions. According to Darwin and Gould we should have discovered the fossil evidence to support both these theories. What we discover is completely opposite their predictions rendering the third premise is false.
 John Angus Campbell and Stephen Meyer, eds., Darwinism, Design, and Public Education (MichiganStateUniversity Press, 2003) pg. 343
 Douglas Erwin, James Valentine, and J. J. Sepkoski A Comparative Study of Diversification Events: The Early Paleozoic versus the Mesozoic (Evolution 41 1987) pgs. 1177-86
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