Encyclopedia of Evolution.pdf - Online Reading Center

Laetoli footprints See australopithecines.
Lamarckism This theory is named for the French scientist
Jean-Baptiste-Pierre-Antoine de Monet, Chevalier de Lamarck
(1744–1829). Lamarck’s theory is most remembered for the
inheritance of acquired characteristics: That is, things that
happen to an organism during its lifetime can be passed on
to future generations. The example most often cited is that
giraffes got their long necks because each generation stretched
their necks a little further trying to reach for food in tall trees.
This theory, now universally understood as false, is usually
blamed on Lamarck. However, the inheritance of acquired
characters was only part of his theory, and it was a view that
was held widely by scientists before, during, and even long
after his lifetime, including a few in the 20th century, long
after the rediscovery of Gregor Mendel’s work (see Mendelian
genetics; Lysenkoism).
Born in an aristocratic but impoverished family, Lamarck
served in the army, and only when he had to quit for health
reasons did he study medicine and biology. He was 44 when
he was appointed to a position at the French Royal Gardens
and 50 before he became a professor at the Natural History
Museum in Paris. Although his reputation was overshadowed
by that of paleontologist Georges Cuvier (see Cuvier,
Georges), he published significant work in the classification
of plants and insects; in fact, he invented the terms invertebrate
and biology. He died in 1829, blind and poor.
His theory, as put forward in his Philosophie Zoologique
of 1809, included more than the inheritance of acquired characteristics.
He believed that microscopic life-forms were continually
generated from soils and progressed to ever higher
and more complex forms. In this way, organisms filled every
niche of structure and function. One of these lineages had culminated
in the human species. He thus added an evolutionary,
or dynamic, dimension to the old concept of The Great
Chain of Being (see scala naturae).
L
Although this theory was disproved by the work of
Gregor Mendel (see Mendel, Gregor), Mendel’s work
remained unknown until the 20th century. Many scientists
held beliefs about inheritance very similar to those of
Lamarck. Even Darwin (see Darwin, Charles) invented a
theory of inheritance, called pangenesis, which was essentially
the same as that of Lamarck.
Further Reading
Burkhardt, Richard W. The Spirit of the System: Lamarck and Evolutionary
Biology. Cambridge, Mass.: Harvard University Press,
1995.
language, evolution of Language is a type of communication,
involving words and grammar, that appears to be unique
to humans. Evolutionary theories deal with (1) the evolution
of language, that is, the human capacity for it; and (2) the evolution
of languages, that is, the patterns of languages found
throughout the human populations of the world.
The Evolution of Language Ability
No one has fully explained the evolutionary origin of human
language ability. Many animal species have verbal and visual
types of communication that are not true language:
• Sometimes even complex animal communications can
occur without conscious thought. This appears to be the
case with even the most complex vocalizations of birds.
Many birds begin to sing when the pineal gland detects
the lengthening days of spring and produces less melatonin.
Bird vocalization is an example of what scientists
call a fixed action pattern (see behavior, evolution of).
The birds sing when the environment stimulates them to
do so. It does not occur to the birds that their response to
the stimulus may make no sense, for example a mockingbird
singing at night in the winter because artificial lights
have produced a mistaken idea of day length. Birdsong