This is typical Western thinking, focused only on numbers, percentages, data and also of people who have little experiece with the actual societies they are dictating terms to. First of all, one of the basic legal rights of a society is to be able to determine who is a part of that society and not have that imposed from the outside from those who don't even know them or are a legal part of that group. 

Secondly, and more importantly, if you go to a rural community/society you will see that how you function, how you relate is way more than just your genetic makeup. I see people who, from physical appearance, have a lot of outside genetics but from how they interact with their familes and communities, the cultural values they hold, the life they live, the food they eat, the *function* they have in that community, the language they might speak you cannot ever say that they are not part of that society that they are not Native. Who are we to impose our numbers on them?