Geologists nearly abolished the Quaternary, the period in which humans evolved
We live in the Quaternary, the geological period covering the last 2.58 million years of ice ages and the whole span of recognisable humans. Yet not long ago the body that sets the time scale proposed scrapping the name altogether. Quaternary researchers objected, and in 2009 the period was redefined and saved.
The name is a leftover from an old scheme. In 1759 Giovanni Arduino divided the rock layers of northern Italy into four successive orders. Jules Desnoyers coined the word quaternary in 1829 for sediments in France's Seine Basin that were clearly younger than Tertiary rocks, making the fourth order the youngest.
The trouble arose when the International Commission on Stratigraphy, from the 1970s, tried to build one global time scale. It defined Quaternary subdivisions by fossils rather than climate, which put the base of the Pleistocene at 1.805 million years ago, well after the big northern glaciations had begun. The commission then suggested dropping the Quaternary entirely, which the International Union for Quaternary Research found unacceptable. The 2009 compromise moved its start back to the onset of Northern Hemisphere glaciation, first set at 2.588 million years and later revised to 2.58, absorbing a stage formerly counted as Pliocene.
The period has two epochs: the Pleistocene, lasting until about 12,000 years ago, and the Holocene, the current warm interval. A third, the Anthropocene, was proposed to mark humanity's impact since the Industrial Revolution, but the International Union of Geological Sciences rejected it in 2024. What defines the Quaternary is repeated glaciation, driven by Milankovitch cycles, with ice sheets reaching as far as 40 degrees latitude.
Continents have barely moved in that time, but geography has changed dramatically. Falling seas exposed land bridges across the English Channel and the Bering Strait, and turned the Black Sea and the Baltic into freshwater lakes before rising waters refilled them. Glacial meltwater repeatedly scoured the Scablands of the American Northwest, and the shapes of Hudson Bay and the Great Lakes reflect land still rebounding from the last ice age.
Source: Quaternary
