charles_darwin

72
CHARLES DARWIN AND THE ORIGIN OF SPECIES
evolve. For Cope, in particular, that internal mechanism was placed
in each organism by God.
A third group of scientists, sometimes called saltationists but
more often Mendelians, argued that evolution sometimes occurred in
rapid spurts or could occur suddenly: slow and steady transformation
was unnecessary. As early as 1859, in his letter congratulating
Darwin on the brilliance of The Origin of Species, Thomas Huxley
wrote, ‘‘You have loaded yourself with an unnecessary difficulty in
adopting ‘Natura non facit saltum’ so unreservedly. I believe she does
make small jumps’’ 24 In 1900, the rediscovery of Gregor Mendel’s
research on heredity by the botanists Carl Erich Correns (1864–
1933), Erich Tschermak von Seysenegg (1871–1962), and Hugo de
Vries seemed to reveal a new and more plausible explanation for
evolution. The idea that discrete genetic units were passed on from
one generation to another was, to the Mendelians, a more systematic
and mathematically simple way of explaining inheritance. In 1901,
de Vries published the first extended explanation of what he called
‘‘the mutation theory’’ in a book with the same title. His ideas, particularly
the transmission of sudden mutations by genes, were supported
and disseminated by the research of three men in particular:
the British biologist William Bateson (1861–1926), who coined the
term genetics; the American biologist Thomas Hunt Morgan (1866–
1945), whose experiments on fruit flies (Drosophila melanogaster)
established the theory that chromosomes are involved in heredity;
and the Danish botanist Wilhelm Johannsen (1857–1927), whose
distinction between genotype, the genetic constitution of an organism,
and phenotype, the physical characteristics of an organism, are
an important foundation of modern genetics.
The most important consequence of the discussions and disputes
among scientists was that Darwin’s theory about evolution was
virtually ignored. Scientists sought alternative explanations for the
reason why evolution occurred. They were debating the ideas in The
Origin of Species very tangentially. Apart from one or two proponents,
such as Alfred Wallace, Darwinism as Darwin understood it
was a dead theory. Looking back on the period from 1880 to 1920,
the British zoologist Julian Huxley (1887–1975), the grandson of
Thomas Huxley, called it ‘‘the eclipse of Darwinism.’’ 25
Public Reaction to Darwin
The numerous disagreements among scientists about the mechanism
of evolution had unfortunate timing. They occurred just as