Sort through it all, says noted sex researcher and psychiatrist John Bancroft, M.D., director of the Kinsey Institute since 1995, and "the United States is in a mess, as far as sex is concerned." For instance, nearly half of all pregnancies are unintended, with 835,000 teenage pregnancies annually; they are said to cost the United States as much as $15 billion a year.

Research into human sexuality could help improve these dismal numbers, as well as unravel significant medical and psychological mysteries, Bancroft says. Unfortunately, societal discomfort about sex marginalizes - and sometimes condemns - scientific sex research. As a result, he concedes, "It's difficult to think of any important aspect of the human condition about which we know less."

Nonetheless, sex researchers have made progress in psychological and physiological fields. Below is Bancroft's list of today's most important findings on sex.

Orientation isn't a choice. Research shows most people become aware of their sexual orientation around puberty and perhaps as early as age 10. Findings such as the discovery of the so-called gay gene have shown that genetics play a role in determining why a minority of people end up with a same-sex orientation, but Bancroft holds that genes are "just part of the picture. There are far more questions than answers."

Sexuality defines our lives.

Sexuality is central to all of us - even people who aren't sexually active. "It's absolutely fundamental to the organization of human society and has been from the earliest history, " Bancroft says.

Studies show that sexuality plays a significant role in our self-esteem and emotional well-being. "For most people, what they think about themselves as a sexual person is a very important part of how they think about themselves as a human being.

Bancroft explains. "The effect of having a good sexual relationship on one's well-being is very substantial." A 2000 Kinsey survey found that general physical and mental health were strongly correlated to sexual well-being and satisfaction. Poor health tended to increase sexual problems and decrease desire.

There's no "normal"

Decades of scientific inquiry have made clear that sexuality exists on a continuum: No two people are exactly the same in their level of sexual interest, patterns of response or interests. And because of this variability, there really is no such thing as a "normal" frequency of sexual activity or a "normal" number of fantasies. "What is right for two people in a relationship is what works for them," Bancroft says.

Women and men have different needs.

Kinsey was one of the first to question the assumption that female sexuality has the same basis as male sexuality; his finding showed that only a minority of women achieve orgasm through intercourse alone. Continue research has demonstrated the complexity of women's sexuality. A 2003 Kinsey study found that the quality of women's emotional interaction with their partner during sex proved more important than the physical aspects, such as orgasm, in determining sexual satisfaction.

Intimacy becomes more important with age. Although sexual interest and the ease of sexual response tend to decrease with age, the quality of the sexual relationship need not deteriorate. In an AARP survey of close to 1,400 adults over 45, two out of three of those with partners said they were extremely or somewhat satisfied with their sex lives. "Provided both partners can be open with each other; the importance of their sexual relationship may shift in emphasis from shared pleasure to shared intimacy," Bancroft says. Unfortunately, normal changes associated with aging-especially men's inability to achieve consistent erections - often are misinterpreted as a relationship failure.