I think 80% genetics at least, heres why true story....
I was showing very strong ENTP traits from an early age, arguing everything, constantly asking why? Generally being a pain in the ass. Instead of playing with dolls I was more happy pulling things apart to see how they worked and climbing trees with the boys. I also developed a really strong interest in physics and anything science based. As far back as I can remember the pull towards these subjects was so strong I can only describe it as instinct. Neither of my parents had an interest in maths or physics so it wasn't due to nurture (although the love of debate definitely came from my father).
Anyway I never knew my grandfather on my dads side because he died before I was born and he was never really discussed until recently but it turns out I took after him. He had won awards in maths. Not only that when I did my family tree...... unbelievable!!! Certain traits run like lightning which can only be explained through a genetic predisposition. As quite a few are well known within there field so was easy to find out about the kind of person they were and all seem to have strong leanings towards ENTP traits.
Here is a sample of just some of my relatives.....
Source -
Clan Anderson
"Alexander Anderson was acclaimed as a brilliant mathematician in Europe when he published his works on geometry and algebra in Paris between 1612 and 1619. His cousin David Anderson of Finshaugh also had a fine mathematical brain and was known locally as "Davie-do-a'-things"; his best known achievement was to devise a method of removing a large rock which had been blocking the entrance to Aberdeen harbour. The family talent was passed on to a grandson, James Gregory, the inventor of the Reflecting Telescope. A later generation included James Anderson (1739-1808 ); his article on monsoons, for the first edition of the "Encyclopaedia Britannica" predicted, with remarkable accuracy, discoveries made by Captain Cook before he had returned from his expedition to announce them!"
No doubt in my mind that genetics forms THE major factor in predisposition of temperament and raw ability. Environment, the People around us, Interactions, and Particular incidents only serve to nurture what we already have and the opportunities at our disposal. Also developing into healthy or unhealthy version of our type is probably due to the latter also.
As for me I never did become a famous physicist or mathematician life took me in another direction.....I work in marketing for a drinks company now. I get to use me inventive / creative / problem solving side and be around people in a fun environment but the thirst for knowledge on certain science subjects is still as strong as ever.