Similarly, a 2009 study found that craniometrics could be used accurately to determine what part of the world someone was from based on their cranium; however, this study also found that there were no abrupt boundaries that separated craniometric variation into distinct racial groups. Another 2009 study showed that American blacks and whites had different skeletal morphologies, and that significant patterning in variation in these traits exists within continents. This suggests that classifying humans into races based on skeletal characteristics would necessitate many different "races" being defined.