An orangutan called Jenny was the first ape Darwin ever saw--and one of the first ever to appear in the London Zoo. Zookeepers often enhanced the humanlike qualities of these popular exhibits by dressing the animals in children's clothes and teaching them human habits. But Darwin would have seen a resemblance between Jenny and his own offspring without the costuming. When Jenny was angry at her keeper, he wrote, the animal "threw itself down on its back & kicked & cryed like a naughty child.--Do monkeys cry?-they whine like children."

Almost as soon as he started thinking about evolution, Darwin understood this: What applied to plants and animals also applied to people. We had evolved, too. "It is absurd to talk of one animal being higher than another," he wrote in one notebook; in another, "Monkeys make men." At a time when most of his fellow citizens took for granted that we had been created in the image of the divine, such thinking was outrageous--the most radical of Darwin's many radical ideas.

Huxley progression from Man's Place in Nature

©AMNH Library

Brothers Under the Skin

Biologist and teacher Thomas Huxley was known as "Darwin's bulldog." This illustration is from his book on human evolution, published eight years before Darwin's Descent of Man. A gifted and provocative speaker, Huxley often lectured on evolution with his arm draped affectionately over a gorilla skeleton.