Which property of fossils allow scientists to determine the relative rock ages..

theFossils are really important for working out the relative ages of sedimentary rocks.  Geologists have studied the order in which fossils appeared and disappeared through time and rocks. This study is called biostratigraphy. Fossils can help to match rocks of the same age, even when you find those rocks a long way apart. the  layer its on  lower the ground  in the grand cayon the older the fossil it is

.) the observation by semmelweis that more mothers died of childbed fever when their doctors also worked in the morgue