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LAMARCK, JEAN BAPTISTE PIERRE ANTOINE
DE MONET DE (b. Bazentin-le-Petit, Picardy,
France, 1 August 1744; d. Paris, France, 28 December
1829), botany, invertebrate zoology and paleontology,
evolution.
analogues. There were some people at the museum,
however, who were discovering analogues. Alexandre
Brongniart and, slightly later, Faujas de Saint-Fond
and Étienne Geoffroy Saint-Hilaire were investigating
similarities between some fossil and living reptiles.
Several naturalists, including Faujas, expected
Lamarck's investigations of shells from living and
fossil forms to resolve the issue. His work did reveal
a number of analogues. The question then became one
of explaining the similarities and differences. Although
the existence of analogues would rule out the possibility
of a general catastrophe, more limited violent
events could have produced some species extinction
which would account for the failure to find analogues
in many cases. There were, Burkhardt suggests, two
other ways to explain the differences: migration or
evolution. Lamarck, unable for philosophical reasons
to entertain the possibility of extinction and unconvinced
of migration as a plausible way to account
for all the differences, chose an evolutionary explanation
sometime in late 1799 or early 1800. Differences
between living and fossil forms existed precisely
because organisms had undergone change over time;
Lamarck regarded this position as one of the strongest
arguments against extinction. The study of fossil
forms led Lamarck to conceive of nature as existing
in time. Lamarck has often been called the founder of
invertebrate paleontology. His most important work
on the subject was Mémoires sur les fossiles des
environs de Paris (1802-1806). The “Introduction” to
this work discusses the significance of fossils for a
theory of the earth.
Geology.
Lamarck's geology was closely connected
with his work in other fields. His Hydrogéologie,
which grew out of a 1799 memoir presented to the
Academy and his work in invertebrate paleontology,
was published in 1802. He originally intended it to be
a much broader work, as the manuscript shows
(Muséum National d'Histoire Naturelle, Paris, MS
756-1, 2). It was to have been a terrestrial physics
including meteorology, geology, and biology, a term
he coined. He had not only a sense of the interrelation
of fields but, within geology, a vision of the whole. He
saw all of nature working according to similar
principles: general natural tendencies producing
gradual change over long periods of time, with local
circumstances explaining the irregularities. His approach
to geology was similar to that in other sciences:
concern with the general principles and contempt for
those who interested themselves too much with the
specifics.
Although Lamarck's geological views were not
original (he was strongly influenced by Buffon and
Daubenton, among others), they were an important
part of his conception of nature. His preoccupation
with marine fossil shells had a decisive influence on
his choice of geological theories. Since such shells had
to have been laid down in water, he needed a theory to
explain how this was possible. As in his meteorology,
he used the moon as the main cause, in this case of a
constant slow progression of the oceans around the
globe. The main geological force was water acting
according to uniformitarian principles over millions
of years. The substances of the mineral kingdom were
produced by the progressive disintegration of
organic remains; water operated on these products
to produce geological formations such as mountains.
Lamarck's uniformitarianism and great geological
time scale have led some to say that he was his own
Lyell. Some historians have thought that Lamarck's
perception of a slowly changing environment and the
resulting necessity of organisms to change or become
extinct (a possibility he could not accept) led him to
his theory of evolution.
Theory of Evolution.
Before beginning a discussion
of Lamarck's theory of evolution, it is important to
point out that he never used the term “evolution” but,
rather, spoke of the path or order which nature had
followed in producing all living organisms. “Evolution”
is used here only as a shorthand form for
Lamarck's longer phrases.
Lamarck's first public presentation of his theory
of evolution was in his opening discourse for his
course on invertebrates at the museum in 1800; it was
published the following year at the beginning of his
Système des animaux sans vertèbres. The evolutionary
views sketched in the discourse leave much to be
desired in terms of organization and explanation.
They are, however, very much a part of a total view
of nature, many aspects of which Lamarck had long
accepted. Natural products consisted of living and
nonliving things; in the two branches of living organisms,
Lamarck pointed out the “degradations” in
structural organization of the larger classificatory
groupings or “masses” as one moved down the series
from the most complex to the simplest. He indicated
his lack of clarity about the new views he was proposing
by using the term “complication” interchangeably
with “degradation.” Nature, after having formed the
simplest animals and plants directly, produced all
others from them with the aid of time and circumstances.
In 1800 Lamarck did not explain how spontaneous
generation occurred or how unlimited time and
varied circumstances produced all other organisms.
He did suggest that, for animals, changing circumstances
and physical needs led to new responses which
eventually produced new habits; these habits tended to
strengthen certain parts or organs through use.