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A Modern Unified Theory of Evolution 201
you with whom I really discussed my problems while I put them down on paper.
Perhaps you can read this between the lines of some of the passages” (24 January
1946).
Stresemann praised Mayr’s Systematics and the Origin of Species as “a synthesis
of taxonomic, genetic, and biological ways of viewing evolution, … [which] will
long remain a reliable guide for systematists working in the complicated labyrinth
of phenomena through which his predecessors had tried vainly to find their way
during the past 150 years” (1951: 281, 1975: 277–278).
The new systematics had a significant impact on the development of population
genetics, and genetics in turn profoundly influenced the ideas of new systematists.
Mayr (1948c) reviewed this progress in the field of systematics for the benefit of
geneticists (polytypic species and trinominal nomenclature, population thinking,
biological species concept). A majority of scientists now agreed on the following
seven statements (Mayr 1948c): (1) Animal species taxa have reality in nature
and are well delimited except in borderline cases; (2) The species concept is defined
biologically, using reproductive isolation as a criterion; (3) Species are composed
of distinct populations (subspecies or geographical races); (4) All characters
(morphological, ecological, physiological) are subject to geographical variation;
(5) Geographical separation results in genetic differentiation which varies among
species; (6) Isolating mechanisms will inhibit the interbreeding of the daughter
populations when they come in secondary contact; (7) Except in borderline cases,
“bridgeless gaps” in morphological and other phenotypical features separate sympatric
species. These considerations changed the entire field of animal taxonomy
(Huxley 1940, 1942; Mayr 1942e). A revolution had occurred—a change from
the static species concept of Linnaeus to the dynamic species concept of modern
systematics.
In the years since 1942 many North American systematists have told Mayr that
his book had entirely changed their professional lives. They had been conventional
taxonomists, had described new species and made generic revisions, but had never
risen above the essentially descriptive level. It was Mayr’s book that showed them
the immense potential of systematics and demonstrated to them that systematics
at the species level occupied an important realm that was inaccessible either
to the geneticist dealing with the gene level or the paleontologist dealing with
phyletic lines and higher taxa. The volume was a real revelation to the traditional
taxonomists. One of them was Ralph Chermock, an assistant professor at the University
of Alabama and E. O. Wilson’s teacher in 1947. As the latter wrote in his
autobiography:
“The prophets of the Chermock circle were the architects of the Modern Synthesis
of evolutionary theory. […] The sacred text of the Chermock circle was Ernst
Mayr’s 1942 work Systematics and the Origin of Species. Mayrwasthecuratorof
birds at the American Museum, but his training had been in Germany, a source of
added cachet. The revolution in systematics and biogeography that Mayr promulgated
was spreading world-wide but especially in England and the United States.
[…] The Modern Synthesis reconciled the originally differing world-views of the
geneticists and naturalists. […] The naturalists were given a hunting license, and