Still, the majority of mammals didn't get much larger than a pig until the Eocene epoch, which began about 55 million years ago. Then a rapid increase in global temperature encouraged the spread ...

The Paleocene and Eocene epochs were crucial periods for the evolution of early mammals, particularly the ancestors of modern primates. During this time, a group of mammals known as ...

Although they came into their own only after the extinction of the dinosaurs some 65 million years ago, mammals had maintained a low-profile existence for some 150 million years before that.