Gesture processing takes place in areas of the brain such as Broca's and Wernicke's areas, which are used by speech and sign language. In fact, language is thought by some scholars to have evolved in "Homo sapiens" from an earlier system consisting of manual gestures. The theory that language evolved from manual gestures, termed Gestural Theory, dates back to the work of 18th-century philosopher and priest Abbé de Condillac, and has been revived by contemporary anthropologist Gordon W. Hewes, in 1973, as part of a discussion on the origin of language.