Measurement of the proportion of fluorine present gives a rough estimate of the time that the bones have been in the ground.
chemical dating An absolute dating technique that depends on measuring the chemical composition of a specimen.
Fossils are important for working out the relative ages of sedimentary rocks.
Throughout the history of life, different organisms have appeared, flourished and become extinct.
On the other hand, non-restrictive relative clauses should be separated from the rest of the sentence by a comma or commas.
For example: In this sentence, the writer is identifying the coat by saying it’s the one Dan was wearing yesterday, as opposed to any other coats he might own.