Such was the case with one man who had a relationship with his horse, according to Daniel Bergner, whose book, "The Other Side of Desire," just arrived in bookstores.
"I find I am closer to horses," the zoophile told Bergner, citing the "trust factor."
Bergner said he sees his characters as "metaphors for our own states of longing" and explores whether sexuality is defined by genetics, as many neuroscientists believe, or through "cultural scripts."
Studies by sexual anthropologist Gilbert Herdt of San Francisco State University reveal that in Papua New Guinea young boys are shepherded through their budding sexuality by engaging in ritualized homosexual oral sex with adolescents, ultimately embracing heterosexuality and siring children.
"Experience molds us," Bergner told ABCNews.com. "There's a sense that a charged experience, whether it is shame, or the opposite -- and pain can easily get mixed with pleasure -- leaves a sexual imprint."
Jacob, who was so ashamed of his foot fetish that he would not share the "monstrosity" with his wife, had struggled painfully through school. One psychiatrist suggested that the fetish began fear, as Jacob looked down, away from the teacher's gaze.
"That moment of terror got translated into an erotic sense of feet," Bergner said. "What we fear, we take control of."
"These two people have transformed each other's lives," he said. "Lust and love here are inseparable and redemptive."
Bergner and others who have interviewed those who cross boundaries most humans would regard as dark territory, say the compulsive power that compels them is part of the universal human story.
"No one wants to talk about Freud any more," he said. "One thing he knew that no scientist or psychologist displaces is that this drive is so central, so essential, and so powerful. The fact that we are living with that kind of powerful drive within in us is inherently threatening."
"Part of me thinks people are more receptive and comfortable taking risks sexually," said Bergner. "But part of me thinks we are pretty much afraid -- afraid because the force of the erotic is pretty strong and probably anarchic, and therefore, maybe we worry that if we step a little over the boundaries, we might not be able to step back."