(i) Large number of organism got buried due to disasters like flood, earthquake, volcano,etc.
(ii) Remnants and impressions of such orgaisms remain preserved underground. These are called as fossils.
(iii) With help of carbon-dating technique, it is easy to determine the age of fossils.
(iv) Once the age of fossil has been determined, it becomes easy to deduce information about other erstwhile organism.
(v) Hence, study of fossils is an important aspect of study of evolution.