It's Not Easy to Become a Fossil: A Science Friday tidbit by Dave Eshleman
At first glance, fossils don't appear to be uncommon. You can routinely buy them in rock and curio shops, although, if affordable, they're most likely to be imprints of leaves or prehistoric clams. Dinosaur fossils? Those are a great deal rarer, and hence a bit pricier. A nearly complete Stegosaurus recently sold for $44.6 million.
It's been estimated that less than one bone in a billion ever gets fossilized. Several things must happen for that to occur. First, the creature must die in the right place, preferably in sediments, where, protected from scavengers, it either leaves an impression, or it decomposes without oxygen so that it's molecules can be replaced by dissolved minerals. Then, as the rock is pressed, twisted, folded, and otherwise mauled by tectonic forces, the fossil must retain an identifiable shape. Finally, it must, after millions or hundreds of millions of years, be exposed so that some passing human might recognize it for what it is.
To put that in perspective, if every 300 million or so Americans alive today were to wander into the wilderness to die en masse, future paleoanthropologists MIGHT uncover about 70 bones, or about a third of one complete skeleton.
Fossils are vanishingly rare! Most of what once lived on our planet has left no trace whatsoever. It's been estimated that only one species in ten thousand has made it into the fossil record. Think about that the next time you visit the rock shop!