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Charles Darwin
Young Charles Darwin & His Journey(1831-1836)
In 1831, 21 year-old Charles Darwin
graduated from college. Like many
young people just out of college,
Darwin didn’t know what he wanted to
do with his life. His father wanter him
to become a doctor , but seeing blood
made him sick. Although he
eventually earned a degree in
theology, Darwin was most interested
in the study of plants and animals
and collecting samples from
nature.
Young Charles Darwin & His Journey(1831-1836)
So Darwin signed on for a 5-year voyage around the world to chart the
coastline of South America and some of the islands of the Pacific Ocean. He
served as the naturalist on the British ship the HMS Beagle. During his
journey Darwin collected thousands of plant and animal samples.
He kept careful note of his observations while traveling to some very
interesting places.
Galapagos Islands
One unique place Darwin visited on his
trip was the Galapagos Islands. The
islands are found 600 miles west of
Ecuador in South America
Darwin noticed that
life on the
Galapagos was
similar to
species in South
America, but not
exactly the
same.
This observation puzzled Darwin. Once back in England,
Darwin hypothesized that many of the species on the
Galapagos Islands were descended from South American
species. They may have been brought to the Galapagos
by storms or other circumstances.
The species migrated from South America,
and slowly over many generations adapted
to there new surroundings on different parts
of the islands eventually becoming separate
species.
Darwin’s Tree of Life
All life is connected through evolution
(change over time)
Darwin’s Book: The Origin of Species
(1859)
Provided an abundance of evidence for
evolution and the theory of Natural Selection,
which explains how evolution happens.
Influences on Darwin
• Geology & Charles Lyell
• Selective Breeding (Artificial Selection)
• Population Control & Thomas Malthus
• Alfred Wallace & his Essay
Charles Lyell &
Geology
During Darwin’s journey on the H.M.S. Beagle he had an opportunity
to read the first volume of his good friend, Charles Lyell’s newly published
book The Principles of Geology. Lyell proposed in his book that the earth
was very old, that it had been slowly changing for millions of years, and
that it was still changing. These changes were taking place from
weathering, erosion and deposition. Most of the geologists of the time did
not think the Earth was old enough to allow for slow changes.
After Darwin returned home from his voyage, he spent a great deal
of time studying his notes, reading, and conversing with colleagues. He
incorporated the ideas from Lyell’s book about the earth into his own
thoughts on how life changes on earth. Using Lyell’s hypothesis, Darwin
concluded that gradual geologic changes over long periods of time could
cause life to change over that same long period of time.
Charles Lyell (1797-1875)
If the earth is
extremely old
and can
change slowly
overtime, life
must change
with it.
Holstein
Jersey
Hereford
Selective Breeding
(Artificial Selection)
Darwin also studied the selective breeding of domestic animals and
crops. By selecting parents with the most desirable traits, farmers and
animal breeders can raise more desirable offspring. Breeders, for instance,
select cattle for increased milk production (Holstein), for high-butterfat milk
(Jersey), or for meat (Hereford). Animal breeders and farmers determine
which members of the population shall reproduce and which shall not. Any
domesticated plant or animal bred to produce desirable characteristics is the
result of artificial selection. The striking changes produced over relatively
few generations are powerful proof that species can evolve. Darwin
suspected that a selection process also occurred in nature. If we can select
for useful traits in organisms through selective breeding; why can’t nature
select traits in organisms that make them more successful to survive.
Selective Breeding (animals)
Selective Breeding (plants)
If humans can select traits in species why can’t nature
Thomas Malthus &
Population Control
Shortly after Darwin returned to England, he read An Essay on the
Principles of Population by the economist Thomas Malthus. Malthus
stated in his essay that the human population was growing so fast that the
supply of resources could not keep up with demand. Malthus reasoned
that the human population increases exponentially. For example, if each
pair of parents produced four children, the new generation would have 4
individuals to replace the 2 that had produced them. The next generation
would have 8, the next 16, and so on. This type of population growth will
eventually exceed its available resources. According to Malthus, when a
population exceeds its resources, disasters such as war, starvation, or
widespread disease limit the population’s growth.
Darwin recognized that Malthus’s principles applied not only to
humans, but to all species. Any species can produce many offspring. He
also knew that the populations of all species are limited by starvation,
disease, competition, and predation. Only a limited number of individuals
survive to reproduce. Darwin reasoned that the offspring of the survivors
inherit traits that help the offspring survive in their environment.
Thomas Malthus (1766-1834)
If humans over
reproduce so do
animals in nature,
but competition
keeps populations
in check
Alfred Wallace &
His Essay
In 1858, Alfred Wallace, a young British naturalist and explorer, wrote Darwin
from Malaysia while he was on expedition. Wallace was seeking Darwin’s advice
about a theory he had. At the time Darwin was one of the leading naturalists of
England. However, Wallace had no idea of Darwin’s life work on his theory of
natural selection because Darwin had only shared his ideas with a few close
colleagues. Wallace sent Darwin an essay on his theory and it turned out that
Wallace had struck upon the theory of natural selection that Darwin had been
researching for 20 years. Wallace’s short sketch was far from the massive body of
evidence Darwin had collected, but its core ideas were similar.
Darwin and Wallace agreed that Wallace’s essay should be published along
with a summary of Darwin’s theory. A year later, in 1859, Darwin published his
book under the title The Origin of Species. Darwin’s book was fully supported by
examples and 20 years of research and influence. His theory on how evolution
works was eventually accepted around 1865 by most of the leading scientists of his
time. Without Wallace’s prompting, Darwin might never have published his theory
during his lifetime.
Alfred Wallace (1823-1913)
Also came up
with Natural
Selection, but
didn’t have as
much evidence.