It takes DNA testing to pinpoint a criminal suspect out of all the millions of people who could conceivably committed the crime, but don't forget in this case they know who the body parts are from out of a pool of only 7 known identities. Blood typing alone would help narrow down what belongs to whom. Furthermore, they undoubtedly have *enormously* complete medical records for each for 7 astronauts, so it would take only minutes to compare found bones to X-ray records and match by size, sex, characteristic ridges, or even match blood antigens or other characteristically individual chemical differences to information already on file with the NASA medical records.