I'd always accepted that nagging curiosity as the price of my existence. To admit frustration — wasn't that ingratitude? — I'd always told people that I didn't consider my biological father to be anything but biological. At twenty-two, I found a way of proving this to myself: by following in his footsteps.

I didn't share this plan with my family, or even the middle-aged geneticist who met me on my second visit to the clinic. To enter the program, she explained, I had to submit to rigorous genetic testing, a physical, and regular blood work. I also had to account for my entire family tree: what my relatives had done for a living, if any had gone bald or needed glasses.That was a problem. I couldn't admit that half my family tree was blank.

So I used my non-biological father's family history instead. He was, I'd always told people, my real dad.

I've often wondered how ethical it was to deceive the clinic and its clients, who use these family histories to choose their donor. But as someone who was put into a similar position — not deceived, but denied the truth — I believe that the real problem is society's insistence that we are defined by our paternity, even when it is described in terms as vague as those offered by fertility clinics.

That insistence is a burden to those of us who will never have the chance to know their biological fathers. For those of us conceived through sperm banks, the fault lies less with the donor than the clinic itself, which accommodates its clients and increases its profits by promoting donors as unique products. To become a donor I had to provide baby photos, record an audio tape describing my aspirations and life history, and give my income level. By identifying donors through these "qualifications," while allowing them the choice of not meeting their offspring, fertility clinics have it both ways. They make paternity both relevant and inaccessible, opening an important question for the donor's offspring that may never be answered. In a sense, by lying, I hoped to let go of the question at last.

The question wouldn't let go of me, however. After making more than a hundred donations — nearly enough to pay a year's rent and help with my student loans — I left the program. One day, I decided to browse the clinic's website to see if my donor ID had been removed. That would indicate that all my donations had been used, and thus all my possible biological offspring had been conceived. While visiting the site, I happened to read the history of the bank and learned it had gone under another name back in the '70s. I was shocked to read that its original founder, now dead, shared my middle name. I'd unwittingly applied to the same sperm bank where I'd been conceived.

I now wonder why I answered the clinic's ad in the first place. Did I want to prove my biological father was unimportant, or by retracing his steps, finally learn what little I could about him? Ultimately, neither of my plans succeeded.

"Good news," the clinic geneticist told me on my third visit. "We're accepting you into the program." Among the forms she gave me to complete was a waiver that would allow my child to contact me after turning eighteen, if I agreed. I hesitated, then signed. I told myself I could always decide later.