Nicholas Wade in The New York Times:
Darwin’s theory of evolution has become the bedrock of modern biology. But for most of the theory’s existence since 1859, even biologists have ignored or vigorously opposed it, in whole or in part. It is a testament to Darwin’s extraordinary insight that it took almost a century for biologists to understand the essential correctness of his views. Biologists quickly accepted the idea of evolution, but for decades they rejected natural selection, the mechanism Darwin proposed for the evolutionary process. Until the mid-20th century they largely ignored sexual selection, a special aspect of natural selection that Darwin proposed to account for male ornaments like the peacock’s tail.
And biologists are still arguing about group-level selection, the idea that natural selection can operate at the level of groups as well as on individuals. Darwin proposed group selection — or something like it; scholars differ as to what he meant — to account for castes in ant societies and morality in people. How did Darwin come to be so in advance of his time? Why were biologists so slow to understand that Darwin had provided the correct answer on so many central issues? Historians of science have noted several distinctive features of Darwin’s approach to science that, besides genius, help account for his insights. They also point to several nonscientific criteria that stood as mental blocks in the way of biologists’ accepting Darwin’s ideas.