The Quaternary period (from 2.588 ± 0.005 million years ago to the present) sees the extinctions of numerous predominantly megafaunal species, which result in a collapse in faunal density and diversity and the extinction of key ecological strata across the globe.

The most prominent event in the Late Pleistocene is differentiated from previous Quaternary pulse extinctions by the widespread absence of ecological succession to replace these extinct species, and the regime shift of previously established faunal relationships and habitats as a consequence.

The earliest casualties are incurred at 130,000 BCE (the start of the Late Pleistocene). However, the great majority of extinctions in Afro-Eurasia and the Americas occur during the transition from the Pleistocene to the Holocene epoch (13,000 BCE to 8,000 BCE).

This extinction wave does not stop at the end of the Pleistocene, continuing, especially on isolated islands, in human-caused extinctions, although there is debate as to whether these should be considered separate events or part of the same event.

Among the main causes hypothesized by paleontologists are overkill by the widespread appearance of humans and natural climate change.

A notable modern human presence first appearsduring the Middle Pleistocene in Africa, and starts to establish continuous, permanent populations in Eurasia and Australasia from 120,000 BCE and 63,000 BCE respectively, and the Americas from 22,000 BCE.

A variant of the former possibility is the second-order predation hypothesis, which focuses more on the indirect damage caused by overcompetition with nonhuman predators.

Recent studies have tended to favor the human-overkill theory.