Other critics, perhaps more familiar with the data, question certain aspects of the quality of the fossil record and of its dating.
It is possible that some traces of organisms, like footprints, can become imprint fossils if they are filled with sediments, but these are rare. That organism normally needs to be near an area with a lot of water, like a lake or river.
While the fossil record is incomplete, it still helps lend evidence to the Theory of Evolution.
Fossils are relatively rare because of all of the elements that have to fall into place before an organism can become a fossil.
Most fossils are bones or teeth due to their relative hardness. Most of these organisms are very small, like insects, and need to be completely enclosed in a substance like tree sap (like in the movie ), a tar pit, or water that turns to ice.
Finding complete fossils like this is even rarer than finding parts of organisms.
The half-lives of several radioactive isotopes are known and are used often to figure out the age of newly found fossils.