Index to Creationist Claims,  edited by Mark Isaak,    Copyright © 2004

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Claim CC201:

Source:

Response:

1. The idea that gradual change should appear throughout the fossil record is called phyletic gradualism. It is based on the following tenets:
   1. New species arise by the transformation of an ancestral population into its modified descendants.
   2. The transformation is even and slow.
   3. The transformation involves most or all of the ancestral population.
   4. The transformation occurs over most or all of the ancestral species' geographic range.
   
   However, all but the first of these is false far more often that not. Studies of modern populations and incipient species show that new species arise mostly from the splitting of a small part of the original species into a new geographical area. The population genetics of small populations allow this new species to evolve relatively quickly. Its evolution may allow it to spread into new geographical areas. Since the actual transitions occur relatively quickly and in a relatively small area, the transitions do not often show up in the fossil record. Sudden appearance in the fossil record often simply reflects that an existing species moved into a new region.
   
   Once species are well adapted to an environment, selective pressures tend to keep them that way. A change in the environment that alters the selective pressure would then end the "stasis" (or lead to extinction).
   
   It should be noted that even Darwin did not expect the rate of evolutionary change to be constant.

   [N]atural selection will generally act very slowly, only at long intervals of time, and only on a few of the inhabitants of the same region. I further believe that these slow, intermittent results accord well with what geology tells us of the rate and manner at which the inhabitants of the world have changed (Darwin 1872, 140-141, chap. 4).

   "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 (Darwin 1872, 152).

   It is a more important consideration . . . that the period during which each species underwent modification, though long as measured by years, was probably short in comparison with that during which it remained without undergoing any change (Darwin 1872, 428, chap. 10).

   "it might require a long succession of ages to adapt an organism to some new and peculiar line of life, for instance, to fly through the air; and consequently that the transitional forms would often long remain confined to some one region; but that, when this adaptation had once been effected, and a few species had thus acquired a great advantage over other organisms, a comparatively short time would be necessary to produce many divergent forms, which would spread rapidly and widely throughout the world (Darwin 1872, 433).
   
   
2. The imperfection of the fossil record (due to erosion and periods unfavorable to fossil preservation) also causes gaps, although it probably cannot account for all of them.
   
   
3. Some transitional sequences exist, which, despite an uneven rate of change, still show a gradual continuum of forms.
   
   
4. The fossil record still shows a great deal of change over time. The creationists who make note of the many gaps almost never admit the logical conclusion: If they are due to creation, then there have been hundreds, perhaps even millions, of separate creation events scattered through time.

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