Epoch· The columns of time

Pleistocene

2.6 Ma → 11.7 ka

The ice ages themselves: two and a half million years of advancing and retreating ice, crossed by at least three kinds of human being.

What the evidence shows

At the coldest moments so much water was locked up in ice that the sea stood 134 metres below its present level, and the main phase of melting, from 16,500 to 8,200 years ago, took more than eight thousand years to give it back. The epoch's rhythm is not steady either: halfway through, the glacial cycles slow and deepen, and no accepted explanation says why. Hominins leave Africa early in the epoch. By a million years ago they are using fire. Our own species appears around 300,000 years ago and shares the ice ages with Neanderthals and Denisovans; pieces of their DNA are still in living genomes.

Bounds and conventions

Its base was lowered from 1.8 to 2.58 million years in 2009, so the epoch gained three-quarters of a million years by a vote rather than by a discovery. Why the glacial rhythm changed a million years ago is unresolved. And using a fire is not the same as depending on one: the earliest secure traces are a million years old, while habitual use is not evidenced in Europe until around 400,000 years ago.

Sources

1. Cohen, K. M., Finney, S. C., Gibbard, P. L., Fan, J.-X. (2013). The ICS International Chronostratigraphic Chart. Episodes 36(3), 199–204, mise à jour continue, voir Cohen et al. (2025), Episodes.
2. Lambeck et al. (2014), PNAS · Sea level and global ice volumes from the Last Glacial Maximum to the Holocene
3. Hays et al. (1976), Science · Variations in the Earth's orbit: pacemaker of the ice ages
4. Ford & Chalk (2020), Oceanography · The mid-Pleistocene enigma
5. Berna et al. (2012), PNAS · Microstratigraphic evidence of in situ fire in the Acheulean strata of Wonderwerk Cave, Northern Cape province, South Africa
6. Hublin et al. (2017), Nature · New fossils from Jebel Irhoud, Morocco and the pan-African origin of Homo sapiens
7. Prüfer et al. (2014), Nature · The complete genome sequence of a Neanderthal from the Altai Mountains
8. Head, M. J. (2019). Formal subdivision of the Quaternary System/Period: Present status and future directions. Quaternary International 500, 32–51.