Geologic time includes divisions of eons, eras, periods, and epochs. Modern humans exist in the Phanerozoic eon, Cenozoic era, Quaternary period, and are currently in the Anthropocene epoch, which describes significant human impact on Earth's ecosystems.
Geologic Time Scale and Modern Humans' Place
Geologic time is categorized into four major divisions, called eons, which are the largest time intervals. The known eons are the Hadean, Archean, Proterozoic, and Phanerozoic, with the first three often referred to collectively as the Precambrian or 'super' eon. Eons are subdivided into smaller units called eras, further divided into periods, then into epochs, and finally into ages. The Phanerozoic eon is the current one and it is subdivided into three eras: the Paleozoic, Mesozoic, and Cenozoic.
Modern humans (Homo sapiens) exist within the Phanerozoic eon, Cenozoic era, Quaternary period, and current epoch known as the Anthropocene. The term Anthropocene is still unofficial and debated but is used to describe the present period of significant human impact on Earth's geology and ecosystems.
The Cenozoic era is notable for having a rich fossil record that allows us to understand the evolution of primates, including humans, with the earliest primates appearing during this era.