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The age of the fossil must be determined so it can be compared to other fossil species from the same time period.Understanding the ages of related fossil species helps scientists piece together the evolutionary history of a group of organisms.When ‘parent’ uranium-238 decays, for example, it produces subatomic particles, energy and ‘daughter’ lead-206.Isotopes are important to geologists because each radioactive element decays at a constant rate, which is unique to that element.Sedimentary rocks are rarely useful for dating because they are made up of bits of older rocks.Uranium is present in many different rocks and minerals, usually in the form of uranium-238.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.

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Volcanic rocks – such as tuff and basalt – can be used in dating because they are formed at a particular moment in time, during an eruption.

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.

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.