The Royal Swedish Academy of Sciences awarded the 2015 Crafoord Prize in Biosciences to Richard Lewontin, professor of biology, emeritus, and Alexander Agassiz Professor of Zoology in the Museum of Comparative Zoology, Emeritus. The award was given for his pioneering analysis and fundamental contributions to the understanding of genetic polymorphism. Lewontin shares the prize with Tomoko Ohta of the National Institute of Genetics in Mishima, Japan.

Until the 1960s, biologists believed that most individuals in a population were fairly similar, genetically speaking. But Richard Lewontin made the revolutionary discovery that genetic variation between individuals in a population was actually very different, and that the variation was many times greater thane expected. The results were published in Genetics in 1966 and aroused a great deal of attention. The first analysis used fruit flies, but the pattern was repeated in every species that the researchers examined: they all demonstrated a significant and unexpected genetic variation, appearing to contradict the principles of natural selection.