Though his ideas had crystallized by 1838, Darwin didn’t publish for fear
that many would ¿ nd them offensive. He published only after another
naturalist, Alfred Russel Wallace (1823–1913), sent him a letter in 1858 that
made it clear that he had stumbled on the same explanation. Darwin’s friend,
geologist Charles Lyell, arranged for the ideas of Darwin and Wallace to be
presented together at a meeting of the Linnaean Society in London on July
1, 1858. The society’s journal published the two presentations in August.
Darwin then set to work to complete the book he had been thinking about
for 20 years, and in 1859, he published On the Origin of Species by Means of
Natural Selection. Priced at 15 shillings, it sold out immediately.
Though quite simple, the idea of natural selection is slippery because it is
statistical. This explains why it is so easily misunderstood. This section will
summarize the argument, step by step, emphasizing that natural selection is
about change not in individuals, but in the average qualities of entire species.
x Species. Species are groups of organisms that can breed with
each other.x Variations. Though members of the same species are similar, there
are always tiny differences, as you can see by looking at the faces
of those around you.x Heredity. Individuals inherit features from their parents.x Fitness. Some features may increase or reduce an individual’s
chances of surviving and reproducing. Poor eyesight is a serious
problem for an eagle!x Differential reproduction. Because of ¿ tness, some individuals have
less chance of surviving and reproducing.x Gradual change. The qualities of individuals with a lesser chance
of reproducing will vanish in subsequent generations while the
qualities of those with greater chances of reproducing will tend to
increase. In this way, the average qualities of entire species will
slowly change.