To reiterate my position from the other day, all statements about what is natural and what is unnatural about human behavior, are suspect. Human behavior is cultural, not instinctual. There are biological absolutes, such as the need to eat, to procreate, etc. However, what we eat, with whom we procreate, etc., are culturally all informed by our culture. So it's really kind of absurd to speak of any human behavior or desire as "unnatural."