Rare Human Behavior is Still Human

Clifford Geertz:

The notion that unless a cultural phenomenon is empirically universal it cannot reflect anything about the nature of man is about as logical as the notion that because sickle-cell anemia is, fortunately, not universal it cannot tell us anything about human genetic processes. It is not whether phenomena are empirically common that is critical in science - else why should Becquerel have been so interested in the peculiar behavior of uranium? - but whether they can be made to reveal the enduring natural processes that underlie them. Seeing heaven in a grain of sand is not a trick only poets can accomplish.

From "The Impact of the Concept of Culture on the Concept of Man" (1965).