Knowing when a dinosaur or other animal lived is important because it helps us place them on the evolutionary family tree.

Accurate dates also allow us to create sequences of evolutionary change and work out when species appeared or became extinct. These are: Where possible, several different methods are used and each method is repeated to confirm the results obtained and improve accuracy.

It's this resetting process that gives us the ability to date rocks that formed at different times in earth history. Carbon 12 and 13 are stable isotopes and the amounts remain the same even in dead material. The ratio of 12 to 14 is about the same in all living things but when a plant or animal dies, no more carbon is taken on.Other critics, perhaps more familiar with the data, question certain aspects of the quality of the fossil record and of its dating.These skeptics do not provide scientific evidence for their views.Instead, other methods are used to work out a fossil’s age.These include radiometric dating of volcanic layers above or below the fossils or by comparisons to similar rocks and fossils of known ages.Our understanding of the shape and pattern of the history of life depends on the accuracy of fossils and dating methods.Some critics, particularly religious fundamentalists, argue that neither fossils nor dating can be trusted, and that their interpretations are better.The process of placing rocks and geologic structures in the correct chronological order.This process does not yield ages in number of years. A volcanic rock chemically equivalent to granite Usually light colored, very fine-grained or glassy-looking.Different methods have their own limitations, especially with regard to the age range they can measure and the substances they can date.A common problem with any dating method is that a sample may be contaminated with older or younger material and give a false age.Radioactive elements are unstable; they breakdown spontaneously into more stable atoms over time, a process known as radioactive decay.Radioactive decay occurs at a constant rate, specific to each radioactive isotope.