Richard Leakey Quote

A vital leap in the evolution of intellectual capacity would have been the ability to form concepts, to conceive of individual objects as belonging to distinct classes, and thus do away with the almost intolerable burden of relating one experience to another. Concepts, moreover, can be manipulated and this is the root of abstract thought and of invention. The formation of concepts is also a necessary, but apparently not sufficient, condition for the emergence of language.

Origins (1977)