Long before paleontology and comparative anatomy took shape as scientific fields in the late 18th century, humanity was aware that certain animal species had vanished from existence. The word extinction initially referred to the extinguishing of flames or settling debts, but it wasnt until 1784 that it was officially linked to the complete disappearance of a species. In 1901, Frederic A. Lucas authored a comprehensive exploration of vertebrate animals, with their sole evidence residing in the fossil records. This work primarily examines vertebrates, spanning from fish to mammals. - Summary by Jeffery Smith