In pre-Columbian art we also find depictions of humans involved in non-reproductive sexual acts, such as anal sex, fellatio and masturbation. These ritual sexual practices served to symbolically link the world of the living with the world of the dead. It seems likely that these practices were associated with the period of the agricultural year when ancient Peruvians acknowledged the presence of their ancestors in the earthly world, in the form of rainfall and the waters that swelled rivers.