The geologic era in which humans have evolved and spread over the Earth is the Cenozoic Era. This time period began roughly 65 million years before the start of the 21st century.
The Cenozoic Era began at the end of the Mesozoic Era when the non-avian dinosaurs and many other animals became extinct. The mass extinction and a cooler, dryer climate left space for new species to evolve. During the Cenozoic Era, mammals became the dominant life form on earth.
Geologists recognize three eras: the Paleozoic Era, the Mesozoic Era and the Cenozoic Era. The time before the Paleozoic Era is referred to as Precambian Time. It is not called an era because there was very little life on earth during this period.