Doug Alves (illustration); Granger Collection (Darwin)

Key Concepts

• Charles Darwin’s insights about evolution have withstood 150 years of scrutiny.
• But evolutionary theory has broadened and changed as his ideas have been melded with genetics.
• Evolutionary biology still must contend with some of the same questions that preoccupied Darwin: What, for one, is a species?

When the 26-year-old Charles Darwin sailed into the Galápagos Islands in 1835 onboard the HMS Beagle, he took little notice of a collection of birds that are now intimately associated with his name. The naturalist, in fact, misclassified as grosbeaks some of the birds that are now known as Darwin’s finches. After Darwin returned to England, ornithologist and artist John Gould began to make illustrations of a group of preserved bird specimens brought back in the Beagle’s hold, and the artist recognized them all to be different species of finches.

From Gould’s work, Darwin, the self-taught naturalist, came to understand how the finches’ beak size must have changed over the generations to accommodate differences in the size of seeds or insects consumed on the various islands. “Seeing this gradation and diversity of structure in one small, intimately related group of birds, one might really fancy that from an original paucity of birds in this archipelago, one species had been taken and modified for different ends,” he noted in The Voyage of The Beagle, published after his return in 1839.

   
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