Fossils> A thing I learned yesterday

I have been reading Bill Bryson's A Short History of Nearly Everything. It does a great job of explaining the scientific history of the world in a very readable style. Yesterday on the train platform I read a great section on fossils and just how rare they are. Estimates are that 1 in a billion bones becomes a fossil. That means that of the entire population of the US alive today there would be about 50 bones that would become fossils, or about a quarter of one skeleton. These bones would be distributed across the entire US and buried, most likely very deeply. So the chances of finding just one of these bones would be miraculous. The fact that so many fossils have been found is a result of billions of years of life on this planet. The reason we have found so many trilobites is because they lived for over 300 million years and in that time were a rather prodigious bunch, forming over 15,000 documented species. To put that into context humans have been around for less than one half of one percent the time that Trilobites existed. To put that into further context, my former cat, Tredeau, could eat a whole watermelon in one sitting.