Most educated
people in Europe and the Americas during the 19th century had their first full exposure to
the concept of evolution through the writings of Charles Darwin
. Clearly, he
did not invent the idea. That happened long before he was born. However, he
carried out the necessary research to conclusively document that evolution has occurred
and then made the idea acceptable for scientists and the general public.
This was not easy since the idea of evolution had been strongly associated
with radical scientific and political views coming out of post-revolutionary
France. These ideas were widely considered to be a threat to the
established social and political order.
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Charles Darwin at age 7 |
Charles Darwin
was born into a moderately wealthy family in Shrewsbury, England. His
father, Robert, had the largest medical practice outside of London at the
time and his mother, Susannah Wedgwood, was from a family of wealthy pottery
manufacturers. She died when Charles was only 8 years old.
Thereafter, he was raised mostly by his father and doting older sisters. Charles grew up in comparative luxury in a large house
with servants. However, this was a socially conservative time in
England that set narrow limits on a young man's behavior and future
possibilities. The constraints on women in Darwin's social class were
even greater. Most were given only enough education to efficiently
manage the homes of their future husbands and raise their children.
Young men were expected to go to university in order to prepare themselves
to become medical doctors, military officers, or clerics in the
Church of England. Most other occupations were considered somewhat
unsavory.
At his
father's direction, Charles Darwin started university at 16 in Edinburgh,
Scotland as a
medical student. He showed little academic interest in medicine and was
revolted by the brutality of surgery being performed without pain relief. Anesthesia was not used for operations until 1842. Darwin dropped out of medical school
after two years of study in 1827. However, his knowledge of natural
history was incidentally enriched in Edinburgh by the teaching of Robert
Grant, a noted professor of anatomy and an avid marine biologist. At
Grant's suggestion, Darwin also became a member of Plinian Society for
student naturalists at the University of Edinburgh.
Having given
up on a medicine as a future career, Charles Darwin's
father then sent him to Cambridge University
in 1828 to pursue an ordinary degree program with the goal of later
becoming an Anglican parson. In Cambridge his life's direction
continued its radical change. He became very
interested in the scientific ideas of the geologist Adam Sedgwick and
the naturalist John Henslow with whom he spent considerable time
collecting specimens from the countryside around the university. At this time in his life, Darwin
apparently rejected the concept of biological evolution, just as his
mentors Sedgwick and Henslow did. However, Darwin had been exposed to
the ideas of Lamarck about evolution earlier while he was a student in
Edinburgh.
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Charles Darwin
1809-1882 |
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Captain Robert
Fitzroy
1805-1865 |
Following
graduation from Cambridge in 1831 with a Bachelor of Arts degree, Darwin was clearly more
interested in biology and geology than he was in a clerical career. Fortunately,
John Henslow was able to help him secure a berth on a British Navy mapping
expedition that was going around the world on what would ultimately become a
nearly
five year long voyage. Initially, Darwin's father refused to allow him
to go but was eventually persuaded by Charles and even agreed to pay for his
passage and for that of his man servant on the journey. They sailed
two days after Christmas in 1831 aboard the survey ship H.M.S. Beagle with Darwin acting as an unpaid naturalist and
gentleman companion
for the aristocratic captain, Robert Fitzroy. Darwin was 22 years old at the
time, and Fitzroy was only 4 years older. The Beagle was a compact 90 foot long ship with a crew of
74. There was little space, even for the captain. Darwin shared a
cramped 10 X 11 foot cabin with two other men, a cabin boy, and their belongings. Because of
the Beagle's design and
small size, it was generally thought by naval men that it was
ill suited for the rough seas it would encounter, especially at the southern
tip of South America. Darwin frequently suffered from sea sickness on
the voyage. Fortunately, he was able to spend most of the time on land
exploring. In fact, he was at sea for only 18 months during the nearly
5 years of the expedition.
Captain Fitzroy was interested in advancing science and was especially
drawn to
geology. He had a
surprisingly good library of over 400 books onboard the Beagle that he made
available to Darwin.
It was during the beginning of the
voyage that Darwin read the first volumes of Charles Lyell's "Principles of
Geology"
and became convinced by his proof that
uniformitarianism provided the
correct understanding of the earth's geological history. This
intellectual preparation, along with his research on the voyage, was critical
in leading Darwin to later accept
evolution. Especially important was his 5 weeks long visit to the Galápagos Islands
in the Eastern Pacific Ocean. It was there that he made the observations
that eventually led him to
comprehend what causes plants and animals to evolve, but he apparently did not
clearly formulate his views on this until 1837. At the time he left
the Galápagos Islands, he apparently still believed in a traditional
Biblical creation of all life forms.
Darwin came to understand
that any population consists of individuals that are all slightly different from one
another. Those individuals having a variation that gives them an advantage in staying
alive long enough to successfully reproduce are the ones that pass on their traits more
frequently to the next generation. Subsequently, their traits become more common
and the population evolves. Darwin called this "descent with
modification."
The Galápagos finches
provide an excellent example of this process. Among the birds that
ended up in arid environments, the ones with beaks better suited for eating
cactus got more food. As a result, they were in better condition to mate.
Similarly, those with beak shapes that were better suited to getting nectar
from flowers or eating hard seeds in other environments were at an advantage
there. In a very real sense, nature selected the best adapted
varieties to survive and to reproduce. This process has come to be
known as natural selection.
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Thomas Malthus
(1766-1834) |
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Darwin did not
believe that the environment was producing the variation within the finch
populations. He correctly thought that the variation already existed
and that nature just selected for the most suitable beak shape and against
less useful ones. By the late 1860's, Darwin came to describe this
process as the "survival of the fittest." This is very different from Lamarck's
incorrect idea that the environment altered the shape of individuals and that these
acquired changes were then inherited.
Nineteenth century critics
of Darwin thought that he had misinterpreted the Galápagos finch data. They said
that God had created the 13 different species as they are and that no evolution in beak
shape has ever occurred. It was difficult to conclusively refute such counter
arguments at that time. However, extensive field research since the
early 1970's has proven Darwin to be
correct.
In
1798, Thomas Malthus
,
an English clergyman and pioneer economist, published Essay on the Principles of Population. In it he observed that human populations will
double every 25 years unless they are kept in check by limits in food
supply. In 1838, Darwin read Malthus' essay and came to realize that all plant and animal populations
have this same potential to rapidly increase their numbers unless they are
constantly kept in check by predators, diseases, and limitations in food, water, and other resources that are
essential for survival. This fact was key to his understanding of the
process of natural selection. Darwin realized that the most fit individuals
in a population are the ones that are least likely to die of starvation and, therefore, are
most likely to pass on their traits to the next generation.
 Who Was Charles Darwin?--video clip from PBS 2001 series
Evolution
requires
RealPlayer to view
(length = 6 mins, 26 secs) |
An example of
evolution resulting from natural
selection was discovered among "peppered" moths living near English industrial
cities. These insects have varieties that vary in wing and body coloration from
light to dark. During the 19th century, sooty smoke from coal burning furnaces
killed the lichen on trees and darkened the bark. When moths landed on these trees
and other blackened surfaces,
the dark colored ones were harder to spot by birds who ate them and, subsequently, they
more often lived long enough to reproduce. Over generations, the environment
continued to favor darker moths. As a result, they progressively became more
common. By 1895, 98%
of the moths in the vicinity of English cities like Manchester
were mostly black. Since the 1950's, air pollution controls have significantly reduced the amount of
heavy particulate air pollutants reaching the trees, buildings, and other
objects in the environment. As a result, lichen has grown back, making trees
lighter in color. In addition, once blackened buildings were cleaned
making them lighter in color. Now, natural selection favors lighter moth varieties so they have
become the most common. This trend has been well documented by field
studies undertaken between 1959 and 1995 by Sir Cyril Clarke from the University
of Liverpool. The same pattern of moth wing color evolutionary change in
response to increased and later decreased air pollution has been
carefully documented by other researchers for the countryside around Detroit, Michigan.
While it
is abundantly clear that there has been an evolution in peppered moth
coloration due to the advantage of camouflage over the last two centuries, it
is important to keep in mind that this story of natural selection in action
is incomplete.
There may have been additional natural selection factors
involved.
Darwin's use of the
phrase "survival of the fittest" is frequently misunderstood. Many
people assume that "the fittest" refers to the strongest, biggest, or
smartest and most cunning individuals. This may or may not be the
case. From an evolutionary perspective, the fittest individuals are
simply the ones who have the combination of traits that allow them to
survive and produce more offspring that in turn survive to reproduce. In fact, they may be relatively
weak, small, and not particularly intelligent. What makes an
individual fit all depends on the environment at the time and the
combination of traits that are most suited to flourishing in it. In
the case of Darwin's finches, specialized beaks provided the advantage.
However, in a changing environment, it is often the versatile generalist who
has the greatest success.
Darwin did not believe
that evolution follows a predetermined direction or that it has an
inevitable goal. His explanation that evolution occurs as a result of
natural selection implied that chance plays a major role. He
understood that it is a matter of luck whether any individuals in a
population have variations that will allow them to survive and reproduce.
If no such variations exist, the population rapidly goes extinct because it
cannot adapt to a changing environment. Unlike Lamarck, Darwin did not
believe that evolution inevitably produces more complex life forms and that
the ultimate result of this process is humans. These were shocking,
revolutionary ideas even for scientists who accepted evolution.
Darwin did not
rush his ideas about evolution and natural selection into print. He first
concentrated his efforts on writing the account of his around the world voyage on the Beagle
and analyzing the many preserved animal and plant specimens and extensive
notes that he brought back with him. This occupied him for more than
10 years. An
additional factor that may have held him back from publishing his ideas
about evolution was the widespread
Christian evangelical fervor in England during the 1830's and 1840's.
He could have been charged with sedition and blasphemy for widely publishing
his unpopular theory.
After returning from the voyage
of the Beagle, Darwin settled down in England, married Emma Wedgwood (his
wealthy first cousin), raised a large family, and quietly continued his
research at his newly purchased country home 16 miles south of London.
In 1842 he wrote a 35 page summary of his theory about evolution. This
was expanded to a 230 page manuscript in 1844, but
it was not published and apparently was only known to a few people in British scientific circles.
Darwin busied himself over the next two decades establishing his reputation
as an important naturalist by growing and studying orchids, pigeons,
earthworms, and other organisms at his home. He spent 8 of these years
studying and writing about barnacles that people had sent him from around
the world.
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Emma Darwin
1808-1896
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Down House--Charles and Emma
Darwin's country
home where he wrote his major publications and
their family lived contentedly for 40 years. |
Charles Darwin
1809-1882
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It
was not until he was 50 years old, in 1859, that Darwin finally published his
theory of evolution in full for his fellow scientists and for the public at
large. He did so in a 490 page book entitled
On
the Origin of Species. It was very popular and controversial from the
outset. The first edition came out on November 24, 1859 and sold out on
that day. It went through six editions by 1872. The ideas
presented in this book were expanded with examples in fifteen additional
scientific books that Darwin published over the next two decades.
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Alfred
Wallace
1823-1913 |
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What finally convinced
Darwin that he should publish his theory in a book for the general educated
public was the draft of an essay that he received in the summer of
1858 from a younger British naturalist named
Alfred Wallace
,
who was then hard at work collecting biological specimens in Southeast Asia
for sale to museums and private collectors. Darwin was surprised to
read that Wallace had come upon essentially the same explanation for
evolution. Being a fair man, Darwin insisted that Wallace also
get credit for the natural selection theory during debates over its validity that occurred at
a meeting of the British Association for the Advancement of Science at
Oxford University in 1860.
We now know that Darwin
deserves most of the credit. In 1837, one year after he returned from
the voyage on the Beagle, he made detailed notes on the idea of evolution by
means of natural selection. At that time, Wallace was only 14 years old. In
addition, it was Darwin's book,
rather than Wallace's essay, that had the most impact on the Victorian public. Darwin
not only described the process of natural selection in more detail, but he also gave
numerous examples of it. It was his On the Origin of Species that
convinced most scientists and other educated people in the late 19th century that life forms do change through
time. This prepared the public for the acceptance of earlier human species and of a
world much older than 6000 years.
Darwin and Victorian Culture--interview with Darwin's biographer,
James Moore
This link takes you to an audio file at an
external website. To return here, you must click
the "back" button on your browser program.
(length = 8 mins, 5 secs) |
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Gregor Mendel
1822-1884 |
Both Darwin and Wallace
failed to understand an important aspect of natural selection. They realized that
plant and animal populations are composed of individuals that vary from each other in
physical form. They also understood that nature selects from the existing varieties
those traits that are most suited to their environment. If natural selection were
the only process occurring, each generation should have less variation until all members
of a population are essentially identical, or clones of each other. That does not happen. Each new generation has
new variations. Darwin was aware of this fact, but he did not understand
what caused the variation. The first person
to begin to grasp why this happens was an obscure Central European monk
named Gregor Mendel
. Through plant breeding
experiments carried out between 1856 and 1863, he discovered that there is a recombination of parental traits in
offspring. Sadly, Darwin and most other 19th century biologists never knew
of Mendel and his research. It was not until the beginning of the 20th century that
Mendel's pioneer research into genetic inheritance was rediscovered. This was long
after his death. He never received the public acclaim that was eventually showered
on Darwin during his lifetime.
Charles Darwin's
convincing evidence that evolution occurs was very threatening to many Christians who
believed that people were created specially by God and that they have not
changed biologically since that creation. The idea that there could have
been prehistoric humans who were anatomically different from us was rejected for similar
reasons. However, Charles Lyell's geological evidence that the earth
must be much older than 6,000 years along with the rapidly accumulating fossil record
of past evolution convinced educated lay people in the 1860's to think what had been
unthinkable earlier.
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Boucher de Perthes
1788-1868 |
Archaeological confirmation
of the existence of prehistoric Europeans had been accumulating since the
1830's. However, until the late 1850's, it had been widely rejected or
misinterpreted. Much of this evidence had been collected by Jacques
Boucher Crčvecoeur
de Perthes
, a customs officer in northern France
during the
early 1800's. His hobby was collecting ancient stone tools from deep
down in the Somme River gravel deposits. Since he found these artifacts
in association with the bones of extinct animals, he concluded that they must
have been made at the time that those animals lived.
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Prehistoric artifact
incorrectly thought
to be a "lightning bolt remnant"
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Boucher de Perthes
tried to
publish his findings in 1838. They were rejected by all important
scientists and scientific journals. The prehistoric stone tools usually were dismissed as being only
"lightning stones" (i.e., the remnants of lightning bolts).
However, by 1858, his claims were beginning to be accepted by some enlightened
Western European scientists. Darwin's publication of On the Origin of
Species the following year convinced even more educated people that
Boucher de Perthes had been right.
Darwin's popularizing
the idea of evolution also made it possible for scientists to begin to accept
that some of the makers of Boucher de Perthes' prehistoric tools had already
been discovered and that their bones were in museums. These bones had
been found in several Western European countries during the first half of the 19th century. However, they had all been dismissed as being from odd
looking modern people. During the 1860's, some were correctly
determined to be from an earlier species or variety of people who had lived
during the last ice age--i.e., long before recorded history. We now know
that these ancient people were mostly Neandertals, who lived about
150,000-28,000 years ago.
NOTE:
Charles Darwin was an active collector of plant and animal
specimens and a prodigious note taker on the voyage of H.M.S. Beagle.
By the time the ship returned to England in 1836, he had accumulated 5,436
plant and animal specimens that had been dried or preserved in alcohol.
He had 368 pages of notes on plants and animals as well as 1,383 pages of
geological observations. In addition, he had a 770 page diary that was
the basis for his later popular book of his narrative on the voyage ("Journal
of Researches Into the Natural History and Geology of the Countries Visited
During the Voyage of H.M.S. Beagle Round the World, Under the Command of
Capt. Fitz Roy, R.N.").
NOTE:
From the time that Charles Darwin published "On the
Origin of Species" in 1859 on up to the present, the presumptions of many
people led them to misread the title. They assumed that it was "On the
Origin of the Species". The implication of inadvertently adding
"the" is that his book was about human evolution. In fact, that was
not the case, though it had implications for human evolution. It
focused on non-human animals and the mechanisms of evolution. He did
not pointedly address the question of human evolution until the publication
of his 1871 book "Descent of Man and Selection in Relation to Sex".
NOTE:
The
phrase "survival of the fittest" was apparently first used in 1851 by the
influential British philosopher Herbert Spencer (1820-1903) as a central
tenet of what later became known as "Social Darwinism." He misapplied
Darwin's idea of natural selection to justify European domination and
colonization of much of the rest of the world. Social Darwinism was
also widely used to defend the unequal distribution of wealth and power in
Europe and North America at the time. Poor and politically powerless
people were thought to have been failures in the natural competition for
survival. Subsequently, helping them was seen as a waste of time and
counter to nature. From this perspective, rich and powerful people did not need to feel
ashamed of their advantages because their success was proof that they were
the most fit in this competition. Despite misgivings by Alfred Wallace
and other naturalists, Charles Darwin began to use "survival of the fittest"
as a synonym for "natural selection" in the 5th edition of Origin of
Species, which was published in 1869.
NOTE:
H.M.S. Beagle, the famous ship that took Charles Darwin on his
1831-1836 voyage around the world, had a rather mundane history following
her return to England.
She was transferred by the British Navy to the Customs and Excise Department
and was used to catch smugglers along the southeast coast of England.
The Beagle was finally sold for scrap in 1870 after 50 years of service.
