On the Origins of New Forms of Life

6: The Fossil Record


Experiments show, that after repeated failures, the union of two recognized species may at last, under very favourable circumstances, give birth to fertile progeny. Such circumstances, therefore, the naturalist may conceive to have occurred again and again, in the course of the great lapse of ages.
——Charles Lyell,
Principles of Geology

The fossil record provides the best and most convincing evidence for the prevalence of stabilization processes. Obviously, the origin of a new type of organism through a stabilization process would have two expected features:

  1. abruptness, the new form would come into being suddenly; and
  2. stability, subsequent to its initial appearance it would remain stable with respect to its characteristic traits indefinitely.

For example, a new polyploid comes into being very rapidly, in one or two generations usually, and is stable thereafter. And, in fact, as this chapter will show, the typical fossil form does conform to the pattern expected for stabilization processes — and, in so doing, fails to conform to the sort of pattern predicted by neo-Darwinian theory. Usually, when a given fossil form is traced down through the geological strata, it remains the same, all the way to the lowermost stratum in which it occurs; the strata below contain different, similarly stable types.

Looking at fossils, then, leads to the conclusion that there is typically a discontinuity in the origin of new forms of life. For the origin of a fossil form usually seems quite abrupt and there is little change thereafter, that is, the typical fossil form appears to arise via saltation. Stabilization theory offers a simple genetic explanation of this finding: Fossil forms that appear to have a saltational origin are assumed to be the products of stabilization processes. In the past, however, saltation has never been accounted for in terms of well-understood genetic processes. Instead, it has merely been set forward as an observation inconsistent with the gradualistic processes posited by neo-Darwinian theory. Many paleontologists have emphasized saltation is the dominant pattern seen in fossils. Georges Cuvier was the first. NEXT PAGE >>