Fossil record
From RationalWiki
The fossil record is one thing that gives significant supporting evidence to the idea that evolution is a rational and real explanation for the origin of the diversity of species. In general, it refers to all fossils that have been excavated, examined and characterised so far by hundreds if not thousands of hardworking scientists and archaeologists over the passed few hundred years. The fossil record is used as evidence for many of things, including common descent, mass extinctions, the Cambrian explosion and that the Earth is considerably older than 6000 years.
At the same time, it is yet another thing which shows that creationist ideas are untenable. Creationists like to point out that there are no transitional fossils (fossils that fill the "gaps" between one species and another) in the fossil record, although this is probably because if one was presented to them, they would point out that there are two new gaps either side of it for which no transitional forms exist. Either that, or they are convinced that the fossil record is a hoax.
Due to the relative rarity of fossil formation (with factors such as time, location and pure luck governing what we can see), and the natural destruction of rock that holds fossils, it is unlikely that the fossil record will ever be 100% complete and comprehensive. Most rationalists, scientists and paleontologists accept this fact and can live with it, noting that we can derrive a lot of information from what we do have rather than dwelling on the infomation that we don't have/haven't found yet.
