The evolutionary biologist George Williams died on Wednesday at the age of 84. He was one of the most important evolutionary biologists of the twentieth century, although he’s not a familiar name beyond scientific circles. Gently, persistently, he reformulated how we think about natural selection and its many effects. As Richard Dawkins noted today, “He was one of the great evolutionary thinkers of my lifetime.”

In 2004, I wrote a profile of Williams for Science. The occasion was a meeting that was held in Williams’s honor, in which one scientist after another stood up to talk about the influence he had had on their work. They investigated everything from human behavior to the mating of fish to disorders of