By the late 1800s, the problem of heredity had acquired a nearmystical aura of glamour, like a Fermat’s Last Theorem for biologists. Like Fermat—the odd French mathematician who had tantalizingly scribbled that he’d found a “remarkable proof” of his theorem, but failed to write it down because the paper’s “margin was too small”—Darwin had desultorily announced that he had found a solution to heredity, but had never published it. “In another work I shall discuss, if time and health permit, the variability of organic beings in a state of nature,” Darwin had written in 1868.

