When I was 42 years old, my mom told me I was adopted. It was a traumatic revelation—for her. She had intended to go to her grave without telling me. For me, though, her confession brought a strange combination of sadness, relief, and even a little elation. In fact, while she was crying I had to turn my head to hide the smile that kept springing up.

I’d always somehow known I was different from my parents. I’m aware that many people say that at some point in their lives—usually as teenagers—but this was a feeling I’d had since I was very small. It was so strong, in fact, that as I grew older and became interested in science, I doubted whether genetic influences were any match at all for environmental influences, and the huge gulf in looks and personality between me and my parents was Exhibit A.

My mom told me I was adopted because my half-sister (whom I had no idea even existed) wrote her a letter explaining that her mother—my birth mother—had died of cancer at age 49, and she thought I needed to know my genetic history.

There’s a much longer story there, and someday I’ll write about it, but I’ll just note here that meeting my birth relatives has been an amazing journey for me. Seeing my physical features (and ailments), interests, and life choices reflected in an entire group of people has made me feel like I’m finally part of the human race, and wasn’t just dropped off by a spaceship.

I have no doubt now that genes are powerful drivers of the Self, of who and how we are in the world.

I’m also very grateful to my half-sister, and to my adoptive mom for having the courage to tell me the truth, although she was terrified to do it. We grew closer without that secret between us. In the last years of her life, we finally had the mother-daughter relationship she’d always wanted us to have.