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Quotations
Ernst Mayr on Gould
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What is particularly delightful about Steve's
writing is the virtuosity with which he connects seemingly unrelated subjects to
illuminate and strengthen his arguments. Whether right or wrong, Steve is always
stimulating, and this is perhaps where he has made his greatest contribution—in
awakening in thousands, if not millions, of his readers an enthusiasm for the secrets
of this wonderful world of ours.
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The widespread neglect of the role of speciation in macroevolution
continued until Niles Eldredge and Stephen Jay Gould (1972)
proposed their theory of punctuated equilibria. Whether one accepts this theory, rejects
it, or greatly modifies it, there can be no doubt that it had a major impact on
paleontology and evolutionary biology.
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The adaptationist program has recently been vigorously attacked
by Gould and Lewontin (1979) in an
analysis which in many ways greatly pleases me, not only because they attack the same
things that I questioned in my "bean bag genetics" paper (Mayr 1959), but also because
they emphasize the holistic aspects of the genotype (Mayr 1970, chap. 10; Essay 24).
Yet I consider their analysis incomplete because they fail to make a clear distinction
between the pitfalls of the adaptationist program as such and those resulting from a
reductionist or atomistic approach in its implementation. I will try to show that
basically there is nothing wrong with the adaptationist program, if properly executed,
and that the weaknesses and deficiencies quite rightly pointed out by Gould and
Lewontin are the result of atomistic and deterministic approaches.
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As a consequence of the adaptationist dilemma, when one
selectionist explanation of a feature has been discredited, the evolutionist must
test other possible adaptationist solutions before he can resign to say: This
phenomenon must be a product of chance. Gould and Lewontin ridicule this research
strategy: 'If one adaptive argument fails, try another one.' Yet this strategy to
try another hypothesis when the first fails is a traditional methodology in all
branches of science.
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The importance of such contraints was, however,
neglected after 1900, when the geneticists thought of evolution as a matter of genes
rather than of whole organisms. And for this reason it has been whloesome that authors
such as Gould and Lewontin (1979) have again called attention to the power of the
constraints on selection.
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I published that theory [of speciational evolution] in a 1954
paper…and I clearly related it to paleontology. Darwin argued that the fossil
record is very incomplete because some species fossilize better than others.…I
noted that you are never going to find evidence of a small local populatlon that
changed very rapidly in the fossil record.…Gould was my course assistant at
Harvard where I presented this theory again and again for three years. So he knew
it thoroughly. So did Eldredge. In fact, in his 1971 paper Eldredge credited me
with it. But that was lost over time.
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Of all the claims made in the punctuationalist theory of Eldredge
and Gould, the one that encountered the greatest opposition was that of
'pronounced stasis as the usual fate of most species,' after having completed the
phase of origination. . . . I agree with Gould that the frequency of stasis in fossil
species revealed by the recent analysis was unexpected by most evolutionary
biologists.
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Quotations
Science and Evolution
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Rapidly evolving peripherally isolated populations may be the
place of origin of many evolutionary novelties. Their isolation and comparatively
small size may explain phenomena of rapid evolution and lack of documentation in the
fossil record, hitherto puzzling to the palaeontologist.
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What is usually forgotten is the important role chance plays
even during the process of selection. In a group of sibs it is by no means
necessarily only those with the most superior genotypes that will reproduce.
Predators mostly take weak or sick prey individuals but not exclusively, nor do
localized natural catastrophes (storms, avalanches, floods) kill only inferior
individuals. Every founder population is largely a chance aggregate of individuals,
and the outcome of genetic revolutions, initiating new evolutionary departures, may
depend on chance constellations of genetic factors. There is a large element of
chance in every successful colonization. When multiple pathways toward the
acquisition of a new adaptive trait are possible, it is often a matter of a
momentary constellation of chance factors as to which one will be taken.
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It is often asked why we do science? Or, what is science good for?
. . . The insatiable curiosity of human beings, and the desire for a better
understanding of the world they live in, is the primary reason for an interest in
science by most scientists. It is based on the conviction that none of the
philosophical or purely ideological theories of the world can compete in the long run
with the understanding of the world produced by science.
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A species consists of a group of populations which replace each
other geographically or ecologically and of which the neighboring ones intergrade or
hybridize wherever they are in contact or which are potentially capable of doing so
(with one or more of the populations) in those cases where contact is prevented by
geographical or ecological barriers.
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Naturalists have known for a long time that island populations
tend to have aberrant characteristics. Wright (1931)(1932, and elsewhere) found the
theoretical basis for this by showing that in small populations the accidental
elimination of genes may be a more successful process than selection. Furthermore,
recessive mutations have a much better chance to become homozygous than in a large
panmictic population. It is therefore very important to learn something about the
actual size of distributional islands and of their populations.
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- Systematics and the Origin of Species. New York: Columbia
University Press, 1942, p. 234.
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An exact determination of the size of an isolated population is
of importance, in view of Sewall Wright's work on gene loss in small populations.
Owing to 'accidents of sampling,' small populations have a trend toward genetic
homogeneity or at least toward a much-reduced variability. This is quite apparent
in taxonomic work, although only a few systematists have taken the trouble to make
careful measurements and to work out the coefficients of variation.
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- Systematics and the Origin of Species. New York: Columbia
University Press, 1942, p. 235.
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