Question: can you be 1/3 of an ethnicity?
Answer: So the answer to this question is No, because there's no power of 2 that includes 3 as a factor. (By definition, powers of 2 don't have any number other than 2 as a factor.) ... With larger numbers of ancestors, you can play with the numbers and get closer to one-third, but you'll never get one-third exactly.