Evolution__3rd_Edition

8 PART 1 / Introduction
Time
(a) (b)
Form of species Form of species
Most biologists in the years just
before Darwin, accepted that
species do not evolve
Time
Figure 1.2
(a) Lamarckian “transformism,” which differs in two crucial
respects from evolution as Darwin imagined it. (b) Darwinian
evolution is tree-like, as lineages split, and allows for extinction.
up trees. The exertion caused their necks to grow slightly longer. Their longer necks
were inherited by their offspring, who thus started life with a propensity to grow
even longer necks than their parents. After many generations of neck stretching, the
result was what we can now see. Lamarck described the process as being driven by the
“striving” of the giraffe, and he often described animals as “wishing” or “willing” to
change themselves. His theory has, therefore, sometimes been caricatured as suggesting
that evolution happens by the will of the organism. However, the theory does not
require any conscious striving on the part of the organism a only some flexibility in
individual development and the inheritance of acquired characters.
Lamarck did not invent the idea of the inheritance of acquired characters. The idea is
ancient a it was discussed in ancient Greece by Plato, for example. However, most
modern thinking about the role of the process in evolution has been inspired by
Lamarck, and the inheritance of acquired characters is now conventionally, if unhistorically,
called Lamarckian inheritance.
Lamarck, as a person, lacked the genius for making friends, and his main rival, the
anatomist Georges Cuvier (1769–1832), knew how to conduct a controversy. Lamarck
had broad interests, in chemistry and meteorology as well as biology, but his contributions
did not always receive the attention he felt they deserved. By 1809, Lamarck had
already persuaded himself that there was a conspiracy of silence against his ideas. The
meteorologists ignored his weather forecasting system, the chemists ignored his chemical
system, and when the Philosophie Zoologique (Lamarck 1809) was finally published,
Cuvier saw to it that this, too, was greeted with silence. However, in reality it was an
influential book. It was at least partly in reaction to Lamarck that Cuvier and his school
made a belief in the fixity of species a virtual orthodoxy among professional biologists.
Cuvier’s school studied the anatomy of animals to discover the various fundamental
plans according to which the different types of organism were designed. Cuvier in this
way established that the animal kingdom had four main branches (called embranchements
in French): vertebrates, articulates, mollusks, and radiates. A slightly different
set of main groups is recognized in modern biology, but the modern groupings do
not radically contradict Cuvier’s four-part system. Cuvier also established, contrary to
Lamarck’s belief, that species had gone extinct (Section 23.2, p. 646).
Lamarck’s ideas mainly became known in Britain through a critical discussion by the
British geologist Charles Lyell (1797–1875). Lyell’s book Principles of Geology (1830–
33) had a wide influence, and incidentally criticized Lamarck (though Lamarckism was
not the main theme of the book). Cuvier’s influence came more through Richard Owen
(1804–1892), who had studied with Cuvier in Paris before returning to England. Owen
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