Jean-Baptiste Lamarck





Jean-Baptiste Pierre Antoine de Monet, Chevalier de Lamarck
(August 1, 1744-December 28, 1829) was a major 19th century
naturalist who coined the term biology.

Lamarck hypothesized a since-discredited mode and mechanism of evolution, in
which individuals adapt during their own lifetimes and transmit traits they
aquire to their offspring. Offspring then adapt from where the parents left
off, enabling evolution to advance. As a mechanism for adaptation, Lamarck
proposed that individuals increased specific capabilities by exercising
them, while losing others through disuse. While this conception of evolution
did not originate wholely with Lamarck, he has come to personify
pre-Darwinian ideas about biological evolution, now called called
Lamarckism.

Born into poor nobility (hence 'chevalier'), Lamarck served in the army
before becoming interested in natural history and writing a multi-volume
flora of France. This caught the attention of Le Comte de Buffon who
arranged for him to be appointed to the Musˇe d'Histoire Naturelle in Paris.

After years working on plants, Lamarck was appointed curator of
invertebrates -- another term he coined. He began a series of public
lectures. Before 1800, he was an essentialist who believed species were
unchanging. After working on the molluscs of the Paris Basin, he grew
convinced that transmutation or change in the nature of a species occurred
over time. He set out to develop an explanation, which he outlined in his
1809 work, Philosophie Zoologique.

Lamarck developed two laws:

  1. In every animal which has not passed the limit of its development, a
     more frequent and continuous use of any organ gradually strengthens,
     develops and enlarges that organ, and gives it a power proportional to
     the length of time it has been so used; while the permanent disuse of
     any organ imperceptibly weakens and deteriorates it, and progressively
     diminishes its functional capacity, until it finally disappears.
  2. All the acquisitions or losses wrought by nature on individuals,
     through the influence of the environment in which their race has long
     been placed, and hence through the influence of the predominant use or
     permanent disuse of any organ; all these are preserved by reproduction
     to the new individuals which arise, provided that the acquired
     modifications are common to both sexes, or at least to the individuals
     which produce the young

Lamarck saw spontaneous generation as being ongoing, with the simple
organisms thus created being transmuted over time (by his mechanism)
becoming more complex and closer to some notional idea of perfection. He
thus believed in a teleological (goal-oriented) process where organisms
became more perfect as they evolved.

Modern science should not vilify Lamarck. At least he believed in organic
evolution at a time when there was no theoretical framework to explain
evolution. He also argued that function precedes form, an issue of some
contention among evolutionary theorists at the time. On the other hand, the
inheritance of acquired characteristics is now widely refuted. August
Weismann disproved the theory by cutting the tails off mice, demonstrating
that the injury was not passed on to the offspring. Jews and other religious
groups have been circumcising men for hundreds of generations with no
noticeable withering of the foreskin among their descendants. However,
Lamarck did not count injury or mutilation as a true acquired
characteristic, only those which were initiated by the animal's own needs
were deemed to be passed on.

Nowadays, the idea of passing on to offspring characteristics that were
acquired during an organism's lifetime is called Lamarckian. The environment
cannot cause hereditary changes, according to the current view. Yet recent
work by E. Jablonka and M. J. Lamb seems to show there is some room for a
sort of 'Lamarckian' evolution, which now goes by the name of epigenetic
inheritance.

Charles Darwin praised Lamarck in the third edition of The Origin of Species
for supporting the concept of evolution and bringing it to the attention of
others. Indeed, Darwin accepted the idea of use and disuse, and developed
his theory of pangenesis partially to explain its apparent occurrence.
Darwin and many contemporaries also believed in the inheritance of acquired
characteristics, an idea that was much more plausible before the discovery
of the cellular mechanisms for genetic transmission. (Darwin, incidentally,
acknowledged his theory would remain somewhat incomplete if the mechanism
for inheritance could not be discovered.)