My husband of eight years confessed to wanting to watch me with another man. I asked if he meant it. He said yes. I asked if he wanted me to set it up. He said yes. I found a guy, and he agreed to a full STD screening — at my husband's suggestion and our expense — so that we wouldn't have to use condoms.

I was worried about how my husband would feel. But he loved every minute of it — he loved it a little too much.

My husband had sex with me after our "guest" left. I still had our guest's semen inside me. Is my husband gay? Is that what cuckolding is all about? He didn't touch the other guy, but what the fuck? — Spouse Expressing Concern Over Newly Disclosed Sexuality

SAVAGE LOVE"Far from being an indication of homosexuality, your husband's turn-on goes back to the roots of male heterosexual experience," says Christopher Ryan, coauthor of Sex at Dawn: The Prehistoric Origins of Modern Sexuality. "Human beings evolved in very intimate groups where sex often involved multiple partners."

Before Ryan walks us through what's so straight about your husband dipping his dick in another man's spunk, SECONDS, let me get this off my chest: Sex at Dawn is the single most important book about human sexuality since Alfred Kinsey unleashed Sexual Behavior in the Human Male on the American public in 1948. Want to understand why men married to supermodels cheat? Why so many marriages are sexless? Why paternity tests often reveal that the "father" isn't? Read Sex at Dawn.

Now back to Ryan:

"Think about it," says Ryan. "Why would women have evolved the capacity for slow-building multiple orgasms while males evolved the orgasmic response of minutemen accompanied by a sudden disappearance of all interest in sex?"

Because — as Ryan and his coauthor Cacilda Jethá lay out in Sex at Dawn — for countless generations, our male and female ancestors, like our closest primate relatives (fuck-mad bonobos), engaged in multipartner sex. Females mated with multiple males, while males — so easily stimulated visually to this day — watched and waited their turn.

"Almost all of us get off on watching other people having sex," says Ryan. "Even if our minds deny it, our bodies respond in many ways, ranging from increased genital blood flow (in both sexes) to stronger male ejaculations."

By inviting another male into your bedroom, SECONDS, your husband — consciously or subconsciously — is inducing what's known as "sperm competition." Watching you have sex with another male made him more excited to have sex with you, not with the other male, and treated him to a more intense orgasm in you, not in the other male.

"So your husband's experience was very heterosexual," says Ryan.

I'll go further: Your husband's experience was the original heterosexual experience.

I am a twenty-four-year-old female. I've been in a relationship with a man for six years, on and off. I love him and think I could spend my life with him. But I have a hard time being faithful. I have cheated on him with other men and with women. He and I are not together currently, but we maintain a long-distance sexual relationship. We say that we are going to be together someday, but he has no trust in me. I would love to be content, but I can't seem to go very long before I get distracted. Please give me some insight! — Don't Wanna Be A Heartbreaker

SAVAGE LOVE"Toward the end of Sex at Dawn," says Ryan, "there's a brief section called 'Everybody Out of the Closet.' We argue that it's not just gay people who have to go through the sort of brutally honest self-exploration involved in coming out. We all need to go through this process — and the sooner the better."

And here's what you need to come out about, DWBAH: You're never going to be happy in a monogamous relationship.

"It's time to stop bullshitting yourself," says Ryan. "You're very young, so, with all due respect, a certain amount of bullshit is to be expected. But you sound ready to move beyond this. Before getting into any sort of committed relationship, you owe it to yourself and to the other person to be honest about who you are, and for now at least, you're clearly not sexually monogamous. The best way to not be a heartbreaker is to be honest about your own feelings.

"And if you'll pardon just a few words of old-guy wisdom while Dan shares his amazing platform," Ryan continues, "many people your age (including yours truly, way back when disco was king) misunderstand the odds of finding love in life. Few young people really appreciate that by being open about who you really are, you end up wasting much less time on relationships that are doomed from the start. In the long run, it's much more efficient to fess up about who you are and what you're really into from the get-go."

Who are you, DWBAH? You're a slut. (I mean that in the sex-positive sense! I'm a slut, too!) And what are you really into? Variety. And don't feel bad: You didn't fail monogamy, DWBAH, monogamy failed you — as it has failed so many others (Clinton, Edwards, Spitzer, Vitter, Ensign, et al.), and will continue to, because monogamy is unrealistic and — this is not a word I toss around lightly — unnatural.

"Maybe half of the people you're interested in will walk away when you fess up," says Ryan. "Let them walk! Those who don't walk away are a much better investment of your time and energy — both of which are more limited than you can possibly realize at age twenty-four."

I've been with my partner for ten years. I have lost all interest in sex, while my partner still has a healthy libido. We've agreed on a weekly "sex night." I dread it. We could call it quits, but we have a child and we love each other. I don't want to break up our family, so I put up with "sex night." It sounds depressing, I know, but the alternative seems worse. — Wishes She Was Horny

SAVAGE LOVE"Here's a dirty little secret: Lots of wonderful marriages aren't particularly sexual or exclusive," says Ryan, hinting at another alternative. "In Sex at Dawn, we show that sexual novelty was an important part of our evolution as a species and why the appetite is still so strong in us today. But, as you and your partner demonstrate, we don't all respond the same way to the absence of novelty.

"You don't say if your loss of libido pertains only to sex with your partner or to anyone at all," Ryan continues, "but it's a good idea to eliminate possible medical and psychological causes before concluding that it's a purely sexual issue. Assuming it's just about libido, I'd encourage you to talk about all this openly and see if you can't find a middle ground that preserves your family and the love you share but incorporates a more comfortable sexual arrangement that doesn't leave your partner frustrated and you dreading 'sex night.'"

In other words, WSWH, give your partner permission to fuck around. Ask yourself what's more important: staying married or staying monogamous?

"If you can find a way to take the pressure off both of you, you might find a deeper intimacy with each other and a return of your libido," says Ryan.

I usually end the column with a plug for my podcast. Not this week: anyone who's ever struggled with monogamy — and any honest person who ever attempted it admits to struggling — needs to read Sex at Dawn. For more about the book, and how order it, go to www.sexatdawn.com.