Are iron chins born or bred?

You are born with it and it also has to do with the environment.

Mexico is full of the indiginious people who I think have the best chin of all. There is indiginious people everywhere but none have proven to have the chin that Mexican fighters do which are composed of Mayans and Astecs. I think it honestly has to do with those bloods just being superior overall. Also they are the only ones that fully kicked out the Spanish, French and English setlers.

We were just meant to be fighters.