A long-delayed reply for @Montmorency.

Quote Originally Posted by Montmorency View Post
I wonder if the variation in faces trends greater the larger in population the ethnic group
I would say necessarily. The larger the population, the stronger the evolutionary pressure needs to be to enforce homogeneity for a given trait. As far as human faces go, that sounds most relevant for sexual selection, and I am not sure it would be up to the task.

Size in numbers also correlates with size in area, so you can have founder effects and other phenomena that push for the branching off of new, distinct ethnic groups.

It didn't jump out at you that he is a Korean-American who basically became a Mexican-American (chicano)? Hence opening a Mexican restaurant.
Adoptees that are adequately young tend to adopt the culture they are adopted into. He would have a much easier time passing as a Mexican than a European where he grew up, so it's not the most surprising cultural identity he adopted.

I get the impression that he has a bit of a conservative personality (cf. the Action facet of the Openness to experience dimension in the NEO PI-R model); he does not seem very interested in trying out new things in general. He was set in his ways before he got to Korea.

If he had ended up in Mexico instead, I don't think he would be very interested in exploring aspects of Mexican culture that he does not already have some familiarity with, because that's how his personality works.