I'm dating an awesome woman I see a future with. However, there's a hurdle: She doesn't want to have sex until we're committed, but I don't feel right about committing without knowing we have sexual chemistry. A previous relationship ended because the sex was subpar, and I don't want to go through that again.

--Conflicted

Sexual chemistry is pretty important. You don't want to get all emotionally attached and then find that sexually, you go together like peanut butter and a repeating saw.

Men and women are alike in countless ways. (Both have two legs; men don't randomly have six like an insect.) However, we differ psychologically per the physical differences we do have; namely, how sex can leave a woman "with child" and a man "with a teaspoon less sperm."

These differences drive men's and women's conflicting "sexual strategies," explains evolutionary psychologist David Buss. For men, a casual sex-centric "short-term sexual strategy" -- hit and run...sex and shun -- has the most "reproductive benefits," increasing men's chances of passing on their genes. Women benefit most from a commitment-centric "long-term sexual strategy" and look for signs a man is emotionally attached, making him more likely to stick around and provide for any, um, sex biscuits they might create.

Where there are deep-seated desires, there's often deception. Buss calls this "strategic interference," describing sneaky tactics used to get the opposite sex to go against their evolutionary best interest. Men, for example, feign commitment to get sex, while women feign sexual interest to get commitment -- either long-term or enough to enjoy an evening of free fine dining. However, we have a defense against this: "negative" emotions -- like a woman's fear of getting humptied and dumptied and a man's fear that all a woman really wants to "ride like a pony" is his American Express black card.

As for what you should do, Buss' research might be helpful. Buss finds that men will shift to a "long-term sexual strategy" when that's what it takes to land a woman of especially high "mate value." If she doesn't seem worth the risk of waiting for, it's probably breakup o'clock. No, sex isn't everything in a relationship. However, if you like to have sex twice a day and your partner's up for twice every never, it's a little hard to meet in the middle -- though the less libidinous partner might come up with some, uh, helpful ideas, such as: "Do we really have to have sex when I'm conscious?"

For pages and pages of "science-help" from me, buy my latest book, "Unf*ckology: A Field Guide to Living with Guts and Confidence." It lays out the PROCESS of transforming to live w/confidence.