If you go by the books, and particularly the Life and Times of Lucas Bishop, he is an aboriginal. But that does not make any sense with how the character was portrayed up until then. So in my head canon, at some point in the future the antimutant sentiment in the USA reached such levels that many mutants fleed to other countries. The australian aboriginals, experienced as they were in racism and persecution, were quite welcoming. So Bishop is a result of that. I also quite like the idea of him being a descendant of Eden Fesi and M. That is why he always knows where he is.