For the gazillion years or so that life would take to begin before it had the ability to eat the evidence, that evidence would react with the environment and leave traces in the form of inedible structures.
Do not assume that you know what is inedible, or how much/little time we are talking about. Schopf (Cradle of Life) estimates something in the low hundreds of thousands of years--I forget exactly--from soup to life.
511 posted on 02/23/2002 7:52:02 AM PST by VadeRetro