There's so many different tribes, and they're all a little different from each other. I've no doubt that some don't grow facial hair at all. And I know some Navajos have Spanish or Mexican blood mixed in. They've told me that a lot of their women were raped when the Spaniards came, and later by Mexican soldiers before the Mexican-American war. There were some mixed race offspring from those times.I never asked what tribe he was descended from, but he didn't have to shave and his face was 'shiny'.
I find their culture absolutely fascinating. I ask a lot of questions about the old ways. When the great toilet paper shortage happened, I asked what the Navajos did to clean up before white people came along. I figured they might have some useful natural solution to the problem. Strangely, no one has been able to answer that yet. The best answer I got was, "I suppose they went downstream from the village and washed their a$$ in the creek!". I then said that I wouldn't want to live in the next village downstream. They laughed and said "**** 'em. If they don't like it they can move..."