After my third date with a guy, he texted and asked why we hadn't had sex yet. I was taking it slow-ish because I was trying to figure out whether I liked him (and vice versa). I was pretty annoyed at his question, and we agreed we should stop seeing each other. Well, last week, he started texting me again. Nothing groundbreaking, just "hey" and "what's up." What's his deal -- does he want another chance? Do I give it to him?

--Unsure

You probably like to wait to have sex till a guy shows you that he's truly interested in who you are -- reflected in his asking questions like, "So, who are your favorite authors?" as opposed to, "Say, can you put your feet behind your head?"

Having sex can leave a woman with a belly of "OMG. How the hell do I pay for orthodontia, rehab, and grad school?" Because of this, female emotions evolved to make women feel unhappy or ambivalent about having sex in the absence of signs a guy cares about them (and will stick around and "invest"). However, men's standards for sex partners tend to be, um, lower: along the lines of, "So, are you female?" (if the man asking is solidly straight) -- and in a pinch: "Are you at least a mammal?"

When the evolved "sexual strategy" that's typically optimal for one sex -- like women taking it slowly -- conflicts with that of the other, "strategic interference" like deception often ensues, explains evolutionary psychologist David Buss. Men feigning commitment to get sex is an example of this. However, with the evolution of this strategy, a deception-circumventing counterstrategy co-evolved in women: defaulting to the assumption they're being conned into bed until proven otherwise.

Chances are the guy's little "where's my sex?!" tantrum resulted from his getting impatient and fed up and falling out of strategic pretendo mode. Buss explains that our emotions are our first line of defense against strategic interference, and right on cue, yours were all "You pig!"

Regarding why the guy's back, he might be bored or desperate -- or think he made a mistake. It's possible he misses you and wants another chance. If you're open to giving him one, make it clear that if he's just looking for a hookup, he's in the wrong place. As for when you might have sex with him, if ever, it'll happen when it happens. (Your vagina is not on a preset timer like a bomb.)

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.