Radiometric dating, on the other hand, is a means of absolute dating. Relative dating can only determine the "order" in which a series of events occurred, not "when" they occurred. Even so, it remains a useful technique. Relative dating by biostratigraphy is the preferred method in paleontology and is, in some respects, more accurate. Steno's Law of Superposition states that older layers will be deeper in a site than more recent layers. This law was the 'relative dating' method of choice in geology from the 17th century to the early 20th century