charles_darwin

Darwin, Darwinism, and Evolution in the Twentieth Century
S. Chetverikov (1880–1959) showed that recessive genes could produce
even more variation in a population. His colleague Aleksandr S.
Serebrovsky (1892–1948) coined the term ‘‘gene pool’’ to explain the
large number of genes available to an organism or population facing
any particular situation during its life. The American biologist Ernst
Mayr (1904–2005) united the ideas of early twentieth-century naturalists
and population geneticists. In Systematics and the Origin of
Species (1942), Mayr argued that species were groups of organisms
that could only breed among themselves. Geographic location, particularly
in isolated areas, could lead to the genes in related individuals
drifting apart as the individuals adapted to their environment:
new species would evolve by natural selection.
The third trend involved the research of paleontologists. The
American George Gaylord Simpson (1902–1984) was one of the first
paleontologists to apply population genetics to the discipline. In
Tempo and Mode in Evolution (1942), Simpson argued that the fossil
record was uneven and irregular. Sometimes evolution occurred
quickly, too quickly for the extinct species to leave a fossil record;
sometimes evolution occurred so slowly that it was impossible to
detect. In either case, Darwin was correct: there would be gaps in
the geological record.
One of the most important points made by scientists involved
in the modern version of Darwinism, Neo-Darwinism, was that Darwin’s
main contention in The Origin of Species was correct. Studying
variation on an easily observed level was the key to understanding
evolution. What Darwin called ‘‘Variation under Domestication’’ and
‘‘Variation under Nature’’ was like observing microevolution. As Darwin
rightly asserted, the continuing accumulation of microevolution
led to something much larger—transmutation or macroevolution.
The ‘‘grand synthesis’’ or ‘‘modern synthesis’’ would have been
enough to solidify Darwin’s reputation as a pioneering scientist. The
discovery of very old hominid, ‘‘human-like,’’ fossils and experiments
by chemists that focused on the origins of life confirmed that Darwin
was one of the greatest scientists since 1500.
In 1924, Raymond Dart (1893–1988), an Australian paleontologist
teaching at the University of Witerwatersrand in South Africa,
obtained a skull that he recognized as belonging to a hominid, a primate
that stood erect and walked on two legs. Dart nicknamed the
fossil ‘‘Taung baby’’ after the area in which it was found. He classified
the fossil Australopithecus africanus (or ‘‘southern ape from Africa’’)
in an article published in 1925. 8 Dart claimed the fossil was an intermediary
between apes and humans. Although most scientists at the
time discounted Dart’s claim, the discovery of more australopithecine
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