| Environ 1 760 résultats  | books.google.fr Also, one must note that Lamarck's theory was in no way a theory of common
descent, supposing that all organisms descend from one or a few common
origins. We know that he thought simple forms of life are constantly being
spontaneously generated through the action of heat, light, electricity, and
moisture on the inorganic world (Philosophie 2:61-90 [236-48]). Then organic
development continues on essentially the same path it started on. Lamarck
believed that lions and so on, ... |
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 | books.google.fr But it is inaccurate to describe students' preconceptions as “Lamarckian” just
because they do not use common descent or natural selection to explain
evolution. Moreover, in many cases, understanding natural selection requires
understanding the mechanisms of heredity and of the origin of genetic variation
through mutations (e.g., Banet and Ayuso 2003).4 Given that the modern notions
of heredity and mutation were unknown to Darwin, it is also inaccurate to
describe the reasoning ... |
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 | books.google.fr ... theory vis-à-vis Lamarckian and neo-Lamarckian transformism, entered an era
of profound ambiguity. We might ask ourselves how could this be so, particularly
since Isidore Geoffroy Saint-Hilaire had devoted dozens of lectures to the topic
and published much on the subject. A number of circumstances propagated and
sustained the ambiguities. First and foremost is the biotheoretical heritage of
Lamarck. His transformism was not premised on the thesis of common descent. It
gave ... |
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 | books.google.fr Lamarck thought that all 13 classes of animals that were recognized in his time
were related to one another in some way, and he traced the origin of most of
them back to worms, based on a series of anatomical comparisons. I have
redrawn his path of common descent from worms to the different Orders of
mammals recognized in his day in Fig. 4.1.2 Lamarck hypothesized that the
transformation of worms branched off into two lineages, one of which led to
Insects, Arachnids (spiders), ... |
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 | books.google.fr His talk in the plenary session struck a masterful balance between the
revolutionary and the traditional, proclaiming the dawn of a new era while also
building bridges to the old establishment and situating Darwin within a familiar
and unthreatening intellectual context that included Lamarck. He argued that
species transformation and common descent were not new with Darwin but had
long been recognized, and that a pantheon of great naturalists was on the
Darwinian side, including ... |
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 | books.google.fr Unlike Darwin, Lamarck didn't suggest common descent, but rather a complex
model in which every type of organism went through a separate evolutionary
process. Nature, he believed, constantly and spontaneously creates new
evolutionary lines, beginning with single-celled animals that have an innate drive
to become more complex, or perfect, over time. Eventually, if the climb isn't
interrupted, they reach the peak of perfection as human beings. But the climb is
often interrupted by ... |
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 | books.google.fr When in 1793 Lamarck (1744–1829) was appointed as Professor of the inferior
animals in France, which he renamed in a less uncomplimentary fashion as the
invertebrates, he came up with new and valid reasons for believing in evolution
and common descent, but then spoiled his case by endowing all animals with a
power to interact with the environment and acquire ever greater complexity or
perfection. Such a 'soft' inheritance of acquired characters has certainly to be
rejected, ... |
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 | books.google.fr But Lamarck never went so far as to say that each of the higher classes is
constantly being produced from the class immediately below it (or that
spontaneous generation takes place to fill the gap or gaps at the bottom of the
scale left by the animals that have become more complex). It is true that
Lamarck's theory, unlike Darwin's, should not be seen as a theory of common
descent. Darwin's emphasis was on common ancestry, as evidenced in his
concluding words of the Origin of ... |
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 | books.google.fr Lamarck and his early followers seem to have believed in multiple parallel lines
of progressive evolution. Although he did provide a diagram of what looks like a
branching tree of relationships, most historians think that Lamarck did not really
anticipate the theory of common descent. Older histories of biology assumed that
Lamarck was marginalized within French science by his archrival, Georges
Cuvier. But recent stud— ies show that there were also radical French naturalists
who ... |
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 | books.google.fr As he goes over the history of evolutionary thought, Raff does not include
Chambers or Darwin grandpère or JeanBaptiste Lamarck (Raff, 14157 passim).
He can even write, "Darwin discovered two of the major themes in evolution,
common descent and natural selection" (144). In no court of historical justice (if
there were such a thing) would Darwin be given credit for common descent. That
should go to E. Darwin, Lamarck, and Chambers, all of whom pushed this idea
far ahead before ... |
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