"The Moche of Peru are another ancient people that sculpted explicit scenes of
sex into their pottery. At least 500 Moche ceramics have sexual themes. The most
frequently depicted act is anal sex, with scenes of vaginal penetration being
very rare. Most pairs are heterosexual, with carefully carved genitalia to show
that the anus, rather than the vagina, is being penetrated. Often, an infant is
depicted breastfeeding while the couple has sex. Fellatio is sometimes
represented, but cunnilingus is absent. Some depict male skeletons masturbating,
or being masturbated by living women.
Rafael Larco Hoyle speculates that their purpose was much different than that of
other early cultures. He states that the Moche believed that the world of the
dead was the exact opposite of the world of the living. Therefore, for funeral
offerings, they made vessels showing sex acts such as masturbation, fellatio and
anal sex that would not result in offspring. The hope was that in the world of
the dead, they would take on their opposite meaning and result in fertility. The
erotic pottery of the Moche is depicted in Hoyle's book Checan." :Wikipedia.