Right now I'm the one with the scratchy face and the plastic breast.

But someday, according to everyone, my daughter is going to find me fascinating. Pepin is going to take my side in arguments, read everything I've ever written like it's Harry Potter, and get her pilot's license just so she can skywrite "Best. Dad. Ever!" on my birthday. For her own birthday, she'll want a Sawzall.

You wait. Scientists have been teasing out the truth in Freud and Jung's queasy theories on mother/son and father/daughter bonds, and recent gene research suggests the old bats were actually right—if for all the wrong reasons (surprise, it's not about having sex with your parents). The X chromosome is loaded with the genes that shape intelligence, cognitive skills, and personality, and sons get their one and only X chromosome from mom. Daughters get an X chromosome from both parents, but only the one from dad corresponds directly to his own X (mom's is random mix of inherited genes). Pepin and I are clones in a way that she and her mom are not—we literally think alike.

Actually, moms, it's worse than that. Last month, researchers announced that even though we inherit the same amount of genetic mutations from both parents, we end up using more from dad. Daughter, son—doesn't matter, both end up more like the parent with hair in the ears.

Imitation is flattery, perhaps, but this isn't really about who Pepin loves—it's about who she is. People say she's starting to resemble me—baby me—and I already feel sorry for her. I don't even look good in shorts, much less a dress; in a necklace, I'd look like the guy who tried to pull out Indiana Jones' heart.

But I'm not going to lie: If she asks to camp together, if she runs some film through these old cameras, if she steals my Dylan records—even his Christmas album—it's going to make life a lot lighter. It's my only hope, really. The other day, a friend dropped something off in a bag with a receipt still in it for the item it originally contained: orthodontic braces and headgear for her daughter's American Girl doll. "A little preview of your life," she said, except we already have an American doll in the house and I didn't even know it until now. I'm not a girl, and Pepin's going to figure that out fast. All I have to stay connected is that X chromosome.

Late at night, giving Pepin her bottle, I'll look up to find her no longer drinking but staring at me, as though awaiting further instructions. I thought I'd gotten off easy when we had a girl: less risk of autism, ADHD, and wearing Zubaz—and I wouldn't have to teach anyone how to be like me. Turns out I was wrong. I may well have a shadow, looking to me for her next move. For now, I simply smile and press the bottle back in her mouth, spooked by the responsibility. If she's really anything like me, she'll understand.

(Photos: Like father, like daughter, great thinkers lounge alike—or vice versa.)