Question: Is eroticism a uniquely human characteristic?
By eroticism I mean something other than sexuality, which is clearly part of our biological natures and shared with other species.
Eroticism is an attribute of mind rather than an observable behavior, and it is difficult, if not impossible, to know what stirs in the brains of our nearest primate kin, or whales, or dolphins.
The safest assumption would be that eroticism is cultural rather than genetic, and uniquely human.
What is eroticism? A state of mind, related to sex, but interior and private. The French philosopher Georges Bataille opines that "eroticism differs from animal sexuality in that human sexuality is limited by taboos and the domain of eroticism is that of the transgression of these taboos." In other words, desire is fueled by culturally imposed restraints. Eroticism, says Bataille, "presupposes man in conflict with himself" (and surely he means "man" to include both men and women).
What sort of taboos? The taboo against nakedness, for example. If we all ran around naked, presumably there would be nothing erotic about nakedness. The peek, the glimpse, and the striptease kindle desire precisely because nakedness is forbidden -- and in many religious traditions, sinful. Adam and Eve disobeyed God and must henceforth cover their bodies, especially their sexual parts. Everyone recognizes the absurd gratuitousness of the nakedness taboo, says Bataille, but the taboo endures. It is almost universal across cultures.
Other prohibitions include the taboo against incest, on sex outside of marriage, on non-generative forms of sex, masturbation, and so on. Some taboos serve biological integrity (the taboo against incest), others might support the orderly organization of society and property (the taboo against extramarital sex), but all have the potential to quicken desire. It would be interesting to know the extent to which sex in the absence of taboos partakes of the erotic. There is a vast speculative literature on this subject, both philosophical and literary, but seeemingly very little science.
In the meantime, there is love and loyalty too, which impose their own taboos -- and the challenge of keeping eroticism alive within the bonds of these freely embraced constraints.