Darwin: Andrew Marr's
Greatest Briton Friday 25 October - 9pm, BBC TWO
Queasiness at the sight of blood curtailed Darwin's medical
career, so he went to Cambridge to study divinity and join the
Church. While there, however, an interest in natural history
was sparked. At 22 he heard of a scientific expedition being
planned, to send scientists to travel the world by ship, the
Beagle. A naturalist was needed and Darwin was
accepted. They set sail on 27 December 1831.
Darwin was influenced by Lyell's Principles of
Geology, which suggested that the fossils found in rocks
were actually evidence of animals that had lived many
thousands, even millions, of years ago. This argument was
reinforced in Darwin's own mind by the rich variety of animal
life and the geological features he saw during his voyage.
Upon reaching South America he observed yet more variety and
began pondering the origin of all these species. The clinching
evidence for the ideas he was forming came in the Galapagos
Islands, home to the Galapagos finches - subjects of some of
Darwin's most famous studies. He observed that while they were
all undeniably finches, they were also very different from
each other.
In
1839 Darwin wrote in his book, The Voyage of the
Beagle: '...one might really fancy that ... one species
had been taken and modified for different ends'. He made
similar discoveries with plants. On James Island, for example,
he found a total of 71 species of flora, and of these 30 were
unique to that island - to the best of his knowledge they
existed nowhere else on earth.
Back in England in 1836, Darwin tried to solve the riddles
of these observations and the puzzle of how species evolve. A
famous essay written on population by Thomas Malthus argued
that any group of animals would continue to breed until there
was insufficient food to feed them all. Darwin realized this
was the key. The implication was staggering - as long as there
was heredity, variation among the offspring, and limited food,
there had to be evolution. Evolution had produced every
creature on earth; by showing how an entirely new species
could evolve, he realised that all species had evolved
He worked on this theory for 20 years, until finally kicked
into action by a letter from Alfred Russel Wallace, who had
come to almost identical conclusions. They published a joint
paper, and in 1859 Darwin published his controversial book
On the Origin of Species by Means of Natural
Selection.
