Gradualism versus Punctuationism
Although modern evolutionists are thought to be divided on the issues
surrounding evolutionary theory, a close look at the evidence suggests that
both the gradualist school of thought and the punctuationist school of thought
share many characteristics in common. This is especially true when evaluating
their beliefs about the fossil record, disagreement with the theory of
saltation, and the misinterpretation of the word “rapid” in terms of
punctuationist theory. Although this may be the case, the two theories do
diverge on one important point, the notion of periods of stasis, but when taken
as a whole, the evidence suggests that punctuationism is not as radical as it
has been hyped up to be.
In terms of evaluating both arguments, it is important to dispel the some
common myths about punctuationist theory. First, there appear to be many large
gaps in the fossil record (Dawkins, 1986). Both gradualists and punctuationists
agree that the only explanation for these apparent gaps, besides the notion
that there are gaps in the record, would be creationism. Creationism holds that
the reason for the appearance of largely different organisms in the fossil
record, without organisms that display intermediate amounts of change is the presence
of a divine creator. Neither gradualists nor punctuationists agree with this
assumption.
In addition, when comparing the theories of gradualism with punctuationism, it
is important to evaluate the theory of saltationism. Although punctuationists
have often been confused with saltationists, this is a huge mistake.
Saltationism holds that macromutations are the cause of evolutionary change
(Dawkins, 1986). This could make sense when viewed in the context of the fossil
record. Saltationists would argue that there really are no gaps in the fossil
record. The dramatic changes noted in the fossil record would be products of
macromutations which are signs of natural selection. This cannot be the case
for two distinct reasons. First, large macromutations are considerably
maladaptive for an organism. In this sense, the size of a mutation will
determine whether the organism will survive and pass on the mutated gene.
Larger mutations will be less likely to be selected, because they will produce
large behavioral abnormalities in the organism, which will significantly impair
the organism in carrying out normal species-typical behaviors for survival. In
turn, the organism will probably die before it is able to successfully
reproduce. In addition, some mutations that are termed macromutations are not
really macromutations at all, but instead small changes in the genetic
instructions that produce large changes in the individual.
It has also been argued, that gradualists believe that evolution proceeds in a
constant fashion. This is also a myth. Both gradualists and punctuationists
believe that evolution proceeds in a somewhat jerky fashion with periods of
evolutionary change being mixed with periods of stasis, or no change (Dawkins,
1986). The main point at which the two theories diverge is on the issue of
stasis. Although both believe that periods of stasis do in fact occur,
punctuationists take this a step further. Punctuationists argue that during
periods of stasis, “There are genetic forces in large populations that actively
resist evolutionary change” (Dawkins, 1986) During these periods of stasis, no
evolutionary change can occur. Eventually though, after a long period of
stasis, the resistant genetic forces are weakened by the forces of evolution,
and a brief period of rapid evolutionary change is allowed to occur. It is also
important to note, that “rapid” in terms of evolution is often misinterpreted.
Even in terms of punctuationist theory, changes are really not rapid in the
general sense of the term. Evolutionary changes are rapid in terms of
geological standards, but by normal standards these changes are very gradual.
In this sense, punctuationists really are arguing from a gradualist
perspective. As Richard Dawkins (1986) put it, punctuationism should be characterized
as “’gradualistic, but with long periods of “stasis” (evolutionary stagnation)
punctuating brief episodes of rapid gradual change’.
Therefore, the theories of gradualism and punctuationism share many elements in
common with one major issue on which they diverge. First, both agree that there
are gaps in the fossil record, and in doing so, they reject the theory of
creationism. Second, neither gradualists nor punctuationists agree with the
tenets of saltationism, because scientific evidence refutes the major premises
of this theory. In addition, both gradualists and punctuationists agree that
evolutionary change does not proceed in a constant and smooth fashion. Both
theories assert that evolutionary change is followed by a period of stasis, but
the punctuationists believe, that this period of stasis is marked by an active
resistance against evolutionary change. Thus, theorists of the punctuationist
school should quit looking to completely discredit the gradualist school of
thought, because they share many premises in common with each other. Instead,
the focus should be placed on identifying the strengths and weaknesses of both
arguments in terms of the fundamental difference concerning periods of stasis.
Reference
Dawkins, R. (1986). The Blind Watchmaker. New York: W. W. Norton.