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Humans’ teeth, which once met in a predator’s vise, slid into an overbite as people turned to the softer foods that agriculture provided, shaping sounds such as “farm,” “vivid,” “fulvous” and “favorite.”

Others come in one of the nearly infinite shades of brown that tax the vocabulary of avian taxonomists: rufous, fulvous, ferruginous, bran-coloured, foxy.

Horace R. Cayton, co-author of the groundbreaking sociological study “Black Metropolis,” sits pensively in a portrait from 1949, his skin lit into fulvous brown by sunlight from a single window.

In the rice fields of eastern Texas, this practice has seriously reduced the populations of the fulvous tree duck, a tawny-colored, gooselike duck of the Gulf Coast.

Shell ventricose, with fulvous spots and white bands; spire slender, acute; suture entire.