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Charles Darwin, British scientist, who laid the
foundation of modern evolutionary theory with his concept of the
development of all forms of life through the slow-working process of
natural selection. His work was of major influence on the life and
earth sciences and on modern thought in general.
Born in Shrewsbury, Shropshire, England, on February
12, 1809, Darwin was the fifth child of a wealthy and sophisticated
English family. His maternal grandfather was the successful china
and pottery entrepreneur Josiah Wedgwood; his paternal grandfather
was the well-known 18th-century physician and savant Erasmus Darwin.
After graduating from the elite school at Shrewsbury in 1825, young
Darwin went to the University of Edinburgh to study medicine. In
1827 he dropped out of medical school and entered the University of
Cambridge, in preparation for becoming a clergyman of the Church of
England. There he met two stellar figures: Adam Sedgwick, a
geologist, and John Stevens Henslow, a naturalist. Henslow not only
helped build Darwin's self-confidence but also taught his student to
be a meticulous and painstaking observer of natural phenomena and
collector of specimens. After graduating from Cambridge in 1831, the
22-year-old Darwin was taken aboard the English survey ship HMS
Beagle, largely on Henslow's recommendation, as an unpaid naturalist
on a scientific expedition around the world.
Darwin's job as naturalist aboard the Beagle gave him
the opportunity to observe the various geological formations found
on different continents and islands along the way, as well as a huge
variety of fossils and living organisms. In his geological
observations, Darwin was most impressed with the effect that natural
forces had on shaping the earth's surface.
At the time, most geologists adhered to the so-called
catastrophist theory that the earth had experienced a succession of
creations of animal and plant life, and that each creation had been
destroyed by a sudden catastrophe, such as an upheaval or convulsion
of the earth's surface. According to this theory, the most recent
catastrophe, Noah's flood, wiped away all life except those forms
taken into the ark. The rest were visible only in the form of
fossils. In the view of the catastrophists, species were
individually created and immutable, that is, unchangeable for all
time.
The catastrophist viewpoint (but not the immutability
of species) was challenged by the English geologist Sir Charles
Lyell in his two-volume work Principles of Geology (1830-33). Lyell
maintained that the earth's surface is undergoing constant change,
the result of natural forces operating uniformly over long periods.
Aboard the Beagle, Darwin found himself fitting many
of his observations into Lyell's general uniformitarian view. Beyond
that, however, he realized that some of his own observations of
fossils and living plants and animals cast doubt on the Lyell-supported
view that species were specially created. He noted, for example,
that certain fossils of supposedly extinct species closely resembled
living species in the same geographical area. In the Galapagos
Islands, off the coast of Ecuador, he also observed that each island
supported its own form of tortoise, mockingbird, and finch; the
various forms were closely related but differed in structure and
eating habits from island to island. Both observations raised the
question, for Darwin, of possible links between distinct but similar
species.
After returning to England in 1836,
Darwin began recording his ideas about changeability of species in
his Notebooks on the Transmutation of Species. Darwin's explanation
for how organisms evolved was brought into sharp focus after he read
An Essay on the Principle of Population (1798), by the British
economist Thomas Robert Malthus, who explained how human populations
remain in balance. Malthus argued that any increase in the
availability of food for basic human survival could not match the
geometrical rate of population growth. The latter, therefore, had to
be checked by natural limitations such as famine and disease, or by
social actions such as war.
Darwin immediately applied Malthus's argument to
animals and plants, and by 1838 he had arrived at a sketch of a
theory of evolution through natural selection (see SPECIES AND
SPECIATION). For the next two decades he worked on his theory and
other natural history projects. (Darwin was independently wealthy
and never had to earn an income.) In 1839 he married his first
cousin, Emma Wedgwood, and soon after, moved to a small estate, Down
House, outside London. There he and his wife had ten children, three
of whom died in infancy.
Darwin's theory was first announced in 1858 in a
paper presented at the same time as one by Alfred Russel Wallace, a
young naturalist who had come independently to the theory of natural
selection. Darwin's complete theory was published in 1859, in On the
Origin of Species. Often referred to as the “book that shook the
world,” the Origin sold out on the first day of publication and
subsequently went through six editions.
Darwin's theory of evolution by natural selection is
essentially that, because of the food-supply problem described by
Malthus, the young born to any species intensely compete for
survival. Those young that survive to produce the next generation
tend to embody favorable natural variations (however slight the
advantage may be)—the process of natural selection—and these
variations are passed on by heredity. Therefore, each generation
will improve adaptively over the preceding generations, and this
gradual and continuous process is the source of the evolution of
species. Natural selection is only part of Darwin's vast conceptual
scheme; he also introduced the concept that all related organisms
are descended from common ancestors. Moreover, he provided
additional support for the older concept that the earth itself is
not static but evolving.
The reaction to the Origin was immediate.
Some biologists argued that Darwin could not prove his hypothesis.
Others criticized Darwin's concept of variation, arguing that he
could explain neither the origin of variations nor how they were
passed to succeeding generations. This particular scientific
objection was not answered until the birth of modern genetics in the
early 20th century.
n fact, many scientists continued to
express doubts for the following 50 to 80 years. The most publicized
attacks on Darwin's ideas, however, came not from scientists but
from religious opponents. The thought that living things had evolved
by natural processes denied the special creation of humankind and
seemed to place humanity on a plane with the animals; both of these
ideas were serious contradictions to orthodox theological opinion.
Darwin spent the rest of his life
expanding on different aspects of problems raised in the Origin. His
later books—including The Variation of Animals and Plants Under
Domestication (1868), The Descent of Man (1871), and The Expression
of the Emotions in Animals and Man (1872)—were detailed expositions
of topics that had been confined to small sections of the Origin.
The importance of his work was well recognized by his
contemporaries; Darwin was elected to the Royal Society (1839) and
the French Academy of Sciences (1878). He was also honored by burial
in Westminster Abbey after he died in Down, Kent, on April 19, 1882. |
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