Neogene Period, the name of the more recent of two periods (the other being the Paleogene Period) into which some geologists divide the Cenozoic Era. The Neogene began about 23,000,000 years ago and extends to the present. It includes the Miocene, Pliocene, and Pleistocene epochs. Most geologists today divide the Cenozoic Era into the Tertiary and Quaternary periods instead of the Neogene and Paleogene periods.
Many scientists believe that the impact from a massive asteroid was what killed off the dinosaurs. It's what started the Age of Mammals. But what if the asteroid had missed?
Every time a new fossil is found, one of the first things scientists determine is how old that fossil really is. But how do they determine it, and how can they be completely accurate?