Encyclopedia of Evolution.pdf - Online Reading Center

Burgess shale
early career. By heating metal spheres and allowing them to
cool, Buffon made one of the earliest estimates of the age of the
Earth (see age of Earth): it was, he said, between 75,000 and
168,000 years old. He was one of the French scientists who,
early in the 18th century, championed a mechanical vision of
the world in which matter, operated on by forces such as gravity,
could explain all that occurs in the natural world. Buffon’s
beliefs conflicted with those of church authorities, but by carefully
worded recantations he was able to avoid disaster. Buffon
also believed that scientific research should provide some practical
benefits to society, which is why he performed research on
such topics as forestry.
In 1739, Louis XV appointed Buffon the director of
the Jardin du Roi (Royal Gardens and Natural History Collections)
in Paris. Thousands of plant, animal, and mineral
specimens had accumulated in this collection from around
the world. Rather than simply cataloging the specimens
contained in the natural history collections, Buffon used his
position as an opportunity to write a natural history of all
plants, animals, and minerals. Beginning in 1749, Buffon and
collaborators published the first three volumes of Histoire
Naturelle (Natural History), which eventually comprised 36
volumes published over a half century. This work was not yet
completed at Buffon’s death. For each animal species in the
Natural History, Buffon described internal and external anatomy,
life stages, breeding habits and behavior, geographical
distribution and variation, economic value, and a summary
of the work of previous naturalists.
Buffon also included essays that were precursors of the
concepts of evolution and of how to define species. He argued
that a species consisted of animals that can interbreed and
produce offspring, which is very similar to the modern concept
of species (see speciation). He performed breeding
experiments, for example, between horses and donkeys, and
between dogs and wolves. Since they produced hybrid offspring
(see hybridization), Buffon concluded that horses and
donkeys, and dogs and wolves, shared a common ancestor.
He classified animals into categories based on their anatomy,
and claimed that “molding forces” of the Earth had modified
primitive stocks of animals into the diversity of animal species
that exists today. These were early evolutionary concepts.
However, he believed that the ability of animals to change was
limited to change within the primitive lineages. Even though
Buffon’s evolutionary concepts were limited, they were among
the earliest serious scholarly proposals that eventually led to
Darwin’s evolutionary theory (see Darwin, Charles).
The Histoire Naturelle was not entirely an objective
work of scientific description. In this book Buffon claimed
that North America was a land of stagnant water and unproductive
soil, whose animals were small and without vigor
because they were weakened by noxious vapors from dark
forests and rotting swamps. He claimed that the lack of
beards and body hair on the Native Americans indicated a
lack of virility and ardor for their females. When Thomas Jefferson
was American Ambassador to France, he wanted to
prove that Buffon was wrong. Jefferson asked a friend in the
American military to shoot a moose and send it to France. It
was not a particularly good moose specimen, and Buffon was
not impressed.
Buffon believed that it was useless to attempt to classify
organisms until they had been cataloged and studied completely.
This put him in conflict with the Swedish scientist Karl
von Linné, who invented the modern taxonomic system (see
Linnaeus, Carolus; Linnaean system). Linné, moreover,
rejected any evolutionary transition. Legend has it that Linné
disliked Buffon enough to name the bullfrog (genus Bufo)
after him. This appears to be untrue, as bufo is the Latin word
for toad, but the coincidence must have pleased Linné.
Buffon’s two principal contributions to evolutionary science
were: First, he established the importance of thoroughly
assembling information about the natural world before proposing
theories about it, a process that is still under way (see
biodiversity); second, he brought up the possibility that life
had, to at least a limited extent, evolved. He died April 16,
1788.
Further Reading
Farber, Paul Lawrence. Finding Order in Nature: The Naturalist
Tradition from Linnaeus to E. O. Wilson. Baltimore, Md.: Johns
Hopkins University Press, 2000.
Roger, Jacques, Sarah Lucille Bonnefoi, and L. Pearce Williams. Buffon:
A Life in Natural History. Ithaca, N.Y.: Cornell University
Press, 1997.
Burgess shale The Burgess shale is a geological deposit in
Canada, from the Cambrian period, in which a large number
of soft-bodied organisms are preserved. Today, the Burgess
shale is high in the Rocky Mountains of British Columbia,
Canada, but during the Cambrian period it was a relatively
shallow ocean floor. About 510 million years ago, mudslides
suddenly buried many of these organisms. In part because of
the rapid burial in fine sediments, and because of the lack of
oxygen, even the soft parts of the organisms (and organisms
that had no hard parts) were exquisitely preserved. It therefore
provides a window into the biodiversity of the Cambrian
period. Other deposits, with specimens similarly preserved,
include the Chengjiang deposits in China and the Sirius Passet
deposit in northern Greenland. During the Cambrian period,
these locations were all tropical, but they were as distant from
one another then as they are now. Many of the organisms are
similar in all three deposits. Therefore the Burgess shale represents
a set of species with nearly worldwide distribution.
The Cambrian period was the first period of the Phanerozoic
era, when multicellular organisms became common. Prior to
the Cambrian period, there were few multicellular organisms
aside from the Ediacaran organisms and some seaweeds.
The relatively rapid origin of a great diversity of multicellular
organisms near the beginning of the Cambrian period has been
called the Cambrian explosion.
Charles Doolittle Walcott was secretary of the Smithsonian
Institution in Washington, D.C. He was a geologist
who had thoroughly explored the high mountains of western
North America for many years. He was nearing the end of
his career when, in late August of 1909, he discovered the