Construction of Gender.... it might find its root way before any social interactions...

Once again, I'm going to have to open the debate between what's biologically acquired and what's socially acquired. I'm pretty sure that after reading Judith Lorber's "Night to His Day: The Social Construction of Gender",  everybody is convinced that the construction of gender is rather social than inborn. So am I. It appears to me that genderism is a giant role playing that everyone is trained to do since age 3. Of course if the training goes well we should be playing the same role for the rest of our lives. Now you might be asking yourself why the training wouldn't go well? Well...., that's where your biological features come into action. Let's say that from birth, you are meant to be a specific gender and your body or brain knows it? It might seem a silly idea, but what brought me to think about that is the case of that (as it is said in Judith Lorber's reading) "... baby boy whose penis was destroyed in the course of a botched circumcision...". That case appears in Judith Lorber's AND Fausto-Sterling's readings. In Judith Lorber's, it clearly says that the construction of gender was "achieved". The use of that word implies it was successful, and I think it might have been. He succeeded to pull out a good "acting performance" throughout his female life. However in Fausto-Sterling's we learn that that same boy, changed into a girl, (in his thirties at the time of the interview) "... never accepted his female identity, and as a teenager demanded to learn his whole medical history and decided to continue life as a male...". So what's perturbing me here is, without knowing anything about his medical history and his brief life as a male, without his parents telling him anything or treating him differently, what was it in his biological man body that gave his "true gender" away? What was it in his subconscious that said: "Hey, wake up! You were born a male, you're not supposed to act, dress or talk like that! " Gender is for sure an ongoing process constructed through your social life, but there might be somewhere deep inside your body something that tells you which way you should be leaning to as a possessor of that type of sex marker.