How Reliable is the Fossil Record?
Our interpretation of the fossil record has been biased by differential preservation. Some species are underrepresented or have not yet been found. We are left with a somewhat blurred picture of the past, especially the early past. Whether an organism is preserved greatly depends on the local environment in which it died. Plants and animals from humid tropical forests are rarely preserved because they decay rapidly in these regions. Similarly, fossils from mountainous areas rarely survive due to high rates of erosion. Desert creatures generally become fossilized more often due to the preserving arid conditions. Likewise, aquatic organisms are often well preserved if their bodies ended up in deep water where there is little oxygen and life. Not all bones from the same animal survive equally well. Lightweight bones with relatively large surface areas deteriorate more quickly and are, therefore, less often fossilized. Small, delicate bones are also more likely to be crushed or carried awa
