There's a peculiar gene prevalent among some ethnicities such as Native Americans that prevents them from growing much facial hair
Facial hair is a characteristic determined genetically. They are just genetically predisposed to not be able to grow a full beard.
Contrary to the popular myth, Native American's can, and sometimes did, grow beards.
"Native American" is way too broad a category here. Some groups are probably...
Most Africans, and native Indians (northern and southern) can't grow beards. Or...
Facial hair begins to develop between the ages of 11 and 16 in males. !
Martin Starr played Martin the one who grew out the beard. !