This period is similar to the Quaternary, but it also includes tool usage by close relatives of humans which were not humans yet.
It ends together with the pleistocene.
Agriculture is not the official definition of the age. But it is good enough. Likely related to the official end of glaciations thing.
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The Cenozoic is the geological era from 66.00 million years ago to the present. It comprises the Palaeogene, Neogene and Quaternary. Its subdivisions organize geological and climate records; their boundaries are defined stratigraphically, with numerical ages calibrated separately.[ref]
International Chronostratigraphic Chart by International Commission on Stratigraphy (2026-06). Cenozoic and Mesozoic columns; numerical ages in Ma