who has 8 grandparents?  :-)

regarding blood as a measure of culture, I heard a CBC interview where the guest complained that simply having native genes did not give one the right to claim to be native (the topic was an ad for testing one's heritage through genetics).
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on the opposite end, a non native kid who was adopted by natives was excluded from a natives only basketball tournament because he had the wrong genes.  He won an appeal but many years later when it was only symbolic
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on the third hand, we allow people to "identify" and chose any gender they like.  Why not culture and heck even race.  That would make Nkechi Amare Diallo happy (you might recognize her original name, Rachel Dolezal)
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Personally the whole concept is hogwash.  If we can't write about things we don't have first hand knowledge then there are no more historical novels, no science fiction, no biography's (only autobiographies), no cookbooks (how can you know what the food feels??) ... it's ridiculous