Primatological data suggest that tools used solely for the enhancement of sexual/sensual pleasure are older than the hominid lineage itself. All the great apes are known to drape themselves in leafy branches. Much of this 'self-decorating' behavior may in fact have a sexual/sensual basis, since the 'decorative' vegetation is often drawn over the nipples and other erogenous zones of the body.
Chimpanzees routinely use stones, sticks and leaves to masturbate and tickle themselves (McGrew 1977). Orangutan females use detached lianas and branches for clitoral stimulation and possibly vaginal insertion (Rijksen 1978). Perhaps early australopithecine females had more pleasurable uses in mind for their digging sticks than simply gathering and processing plant foods.
An excerpt from:
Vasey, Paul
1998 Intimate Sexual Relations in Prehistory: Lessons from the Japanese Macaques. World Archaeology 29 (3): 407-425
