Following the Precambrian Time, Paleozoic Era, and the Mesozoic Era on the Geologic Time Scale is the most recent era called the Cenozoic Era. Following the K-T Extinction at the end of the Cretaceous Period of the Mesozoic Era, the Earth found itself needing to rebuild once again. The Cenozoic Era has spanned the last 65 million years and is continuing to this day.
Now that dinosaurs, besides birds, were all extinct, it gave mammals the opportunity to flourish. The Cenozoic Era was the first era that saw humans evolve. Much of what the common population thinks of as evolution all happened in the Cenozoic Era.
The first period of the Cenozoic Era is called the Tertiary Period. Recently, the Tertiary Period has been broken down into the Paleogene Period and Neogene Period. Most of the Paleogene Period saw the birds and small mammals become even more diverse and grow greatly in numbers. Primates started to live in the trees and some mammals even adapted to live part time in the water.Marine animals didn't have such luck during the Paleogene Period. There were massive global changes that resulted in many deep sea animals going extinct.
The climate cooled significantly from the tropical and humid climate during the Mesozoic Era. This obviously changed the types of plants that did well on land. Instead of lush, tropical plants, land plants became more deciduous plants appeared. The first grass also came into existence during the Paleogene Period.
The Neogene Period saw continuing cooling trends. The climate resembled what it is today and would be considered seasonal. Toward the end of the period, however, the Earth was plunged into an ice age. Sea levels fell and the continents had finally come to about the positions they are in today.
Many ancient forests were replaced with grasses and expansive grasslands as the climate continued to dry out during the Neogene Period. The led to the rise of grazing animals like horses, antelope, and bison. Mammals and birds continued to diversify and dominate.
The Neogene Period is also considered the start of human evolution. It was during this time that the first human like ancestors, the hominids, appeared in Africa. They also moved into Europe and Asia during the Neogene Period.
The final period in the Cenozoic Era, and the period we currently live in, is the Quaternary Period. The Quaternary Period began in an ice age where glaciers advanced and retreated over much of the Earth that are now considered temperate climates like North America, Europe, Australia, and the southern part of South America.
The Quaternary Period is marked by the rise of the human dominance. Neanderthals came into existence and then went extinct. The modern human evolved and became the dominant species on Earth.
Other mammals on Earth continued to diversify and branch off into various species. The same happened with marine species. There were a few extinctions over this time period as well, due to the changing climate. Plants became adapted to the various climates that emerged after the retreating of the glaciers. Tropical areas never had glaciers, so the lush, warm weather plants thrived all during the Quaternary Period. Areas that became temperate had many grasses and deciduous plants. The slightly colder climates saw the re-emergence of conifers and small shrubs.
The Quaternary Period and Cenozoic Era continue on today. They will likely continue until the next mass extinction event occurs. Humans remain dominant and many new species are discovered on a daily basis. While the climate is currently changing once again, and species are also going extinct, no one knows when the Cenozoic Era will end.