The Science Book

144 CHARLES DARWIN

T

he British naturalist
Charles Darwin was by no
means the first scientist
to suggest that plants, animals, and
other organisms are not fixed and
unchanging—or, to use the popular
word of the time, “immutable.” Like
others before him, Darwin proposed
that species of organisms change,
or evolve, through time. His great
contribution was to show how
evolution took place by a process
he termed natural selection. He
laid out his central idea in his
book On the Origin of Species by
Means of Natural Selection, or the

Preservation of Favoured Races in

the Struggle for Life, published in

London in 1859. Darwin described

the book as “one long argument.”

“Confessing a murder”

On the Origin of Species met with

academic and popular opposition.

It made no mention of religious

doctrine, which insisted that

species were indeed fixed and

immutable and designed by God.

But gradually the ideas in the book

changed the scientific perspective

on the natural world. Its core notion

forms the basis for all modern

IN CONTEXT

BRANCH

Biology

BEFORE

1794 Erasmus Darwin

(Charles’s grandfather)

recounts his vision of

evolution in Zoonomia.

1809 Jean-Baptiste Lamarck

proposes a form of evolution

through the inheritance of

acquired characteristics.

AFTER

1937 Theodosius Dobzhansky

publishes his experimental

evidence for the genetic basis

of evolution.

1942 Ernst Mayr defines the

concept of species through

populations that reproduce

only with one another.

1972 Niles Eldredge and

Stephen Jay Gould propose

that evolution occurs mainly in

short bursts interspersed with

periods of relative stability.

biology, providing a simple, but

immensely powerful, explanation

of life forms both past and present.

Darwin was acutely aware of

the potential blasphemy in his

work during the decades he spent

writing it. Fifteen years before

publication, he explained to his

confidant, the botanist Joseph

Hooker, that his theory required

no God or unchanging species:

“At last gleams of light have come,

& I am almost convinced (quite

contrary to opinion I started with)

that species are not (it is like

confessing a murder) immutable.”

Most organisms produce more offspring than

can survive due to constraints such as lack of

food and living space.

If these individuals pass on the advantageous

traits to their offspring, these also survive.

I have called this principle “natural selection.”

Variation means some offspring are better

suited or adapted to the struggle for survival.

Offspring vary from each other in many ways.