The book sets today's defaunation event into its historical setting. The best source of information available to do that is the fossil record. Unfortunately, the fossil record has some inbuilt limitations that affect any analysis that uses it. This chapter starts by outlining these limitations and what we can do limit them. I then look at how the extinction and origination (evolutionary appearance) of species are recorded in the fossil record. This is important as the pattern of extinction and origination of species over deep time forms the basis of the geological time scale that is used throughout the book. Finally, I examine the beginnings of modern extinction studies and the recognition of the Big Five mass extinctions.