The Science Book

148 CHARLES DARWIN

Much later, in his autobiography,
Darwin recalled his reaction when
he first read Malthus back in 1838.
“Being well prepared to appreciate
the struggle for existence...it
at once struck me that under
these circumstances favourable
variations would tend to be
preserved, and unfavourable ones
to be destroyed. The result of this
would be the formation of new
species...I had at last got a theory
by which to work.”
Knowing more about the role of
variation, by 1856 Darwin the pigeon
breeder could imagine not humans
but nature doing the choosing. From
the term “artificial selection” he
derived “natural selection.”

Jolt into action
On June 18, 1858, Darwin received
a short essay by a young British
naturalist named Alfred Russel
Wallace. Wallace described a
flash of insight in which he had
suddenly understood how evolution
occurred, and asked Darwin for
his opinion. Darwin was startled
to read that Wallace’s insight
replicated almost exactly the same
ideas he himself had been working
on for more than 20 years.

Worried about precedence, Darwin

consulted Charles Lyell. They

agreed to a joint presentation of

Darwin’s and Wallace’s papers at

the Linnaean Society in London on

July 1, 1858. Neither author would

attend in person. The audience’s

response was polite, with no outcry

about blasphemy. Encouraged,

Darwin now finished his book.

Published on November 24, 1859,

On the Origin of Species sold out

on its first day.

Darwin’s theory

Darwin states that species are not

immutable. They change, or evolve,

and the main mechanism for this

change is natural selection. The

process relies on two factors.

First, more offspring are born than

can survive when faced with the

challenges of climate, food supply,

competition, predators, and

diseases; this leads to a struggle

for existence. Second, there is

variation, sometimes tiny but

nonetheless present, among the

offspring within a species. For

evolution, these variations must

fulfill two criteria. One: they should

have some effect on the struggle

to survive and breed, that is, they

should help to confer reproductive

success. Two: they should be

inherited, or passed to offspring,

where they would confer the same

evolutionary advantage.

Darwin describes evolution as

a slow and gradual process. As a

population of organisms adapts

to a new environment, it becomes

a new species, different from

Charles Darwin Born in Shrewsbury, England,

in 1809, Darwin was originally

destined to follow his father

into medicine, but his childhood

was filled with pursuits such as

beetle collecting, and with little

inclination to become a physician,

he trained for the clergy. A chance

appointment in 1831 placed him

as expedition scientist on HMS

Beagle’s around-the-world trip.

Following the voyage, Darwin

was under the scientific spotlight,

gaining fame as a perceptive

observer, reliable experimenter,

and talented writer. He wrote

on the formation of coral reefs

and on marine invertebrates,

especially barnacles, which he

studied for almost 10 years. He

also wrote works on fertilization,

of orchids, insect-eating plants,

movement in plants, and

variation among domesticated

animals and plants. Later in life,

he tackled the origin of humans.

Key works

1839 The Voyage of the Beagle

1859 On the Origin of Species by

Means of Natural Selection

1871 The Descent of Man, and

Selection in Relation to Sex

Alfred Russel Wallace, like Darwin,

developed his theory of evolution in the

light of extensive field work, conducted

first in the Amazon River Basin and

later in the Malay Archipelago.