Age· The columns of time

Chibanian

774 ka → 129 ka

The Chibanian, from 774,000 to 129,000 years ago, is defined by a section on the Boso peninsula, in Japan, the only unit of the time scale named after a Japanese locality, and Homo sapiens appeared within it.

Age defined by a section on the Boso peninsula, in Japan, the only unit of the geological time scale named after a Japanese locality, and in which Homo sapiens appears.

What the evidence shows

The Chiba section was ratified in 2020 after a long competition with European candidates, and places the base at about 774,000 years: the level lies within marine isotope stage 19 and close to the Matuyama-Brunhes magnetic reversal, around 773,000 years, the last reversal of the Earth's magnetic field. The age carries the appearance of Homo sapiens, some 300,000 years ago in Africa, and also that of the other contemporaneous human populations: Neanderthals in Europe and western Asia, at least some of whose groups practised unions between close relatives, Denisovans in Asia, and on Flores a population of small-bodied hominins. These lineages were contemporaries, and present-day genomes preserve the trace of their encounters.

Bounds and conventions

Its limit is fixed, and the neighbouring magnetic reversal is among the best dated events of the Quaternary. The appearance of the species is not a date but a decision about which characters count: the Moroccan fossils, dated to 315,000 years with an uncertainty of 34,000 years, are the oldest attributed to it, the face already conforming and the braincase still long and low.

Chiba section GSSP, ratified in 2020.