Late Pleistocene megafaunal extinctions and the overkill-vs-climate debate

Date

c. 15,000 – 10,000 years ago

Category

Environment & climate

Region

Global (especially Americas and Australia)

Era

Prehistory

Significance

Toward the end of the Pleistocene, a wave of extinctions eliminated much of the world's megafauna — animals over about 44 kg — with especially severe losses in the Americas and Australia.

North America lost some 32 genera of large mammals, including mammoths, mastodons, giant ground sloths, glyptodonts, sabre-toothed cats and horses, within roughly two thousand years centred on about 11,000 years ago. Two principal hypotheses compete to explain this. The 'overkill' model attributes the losses to hunting pressure from expanding human populations, citing the close coincidence between human arrival and extinctions on previously uninhabited landmasses. The climate hypothesis instead emphasises rapid environmental upheaval during the glacial-interglacial transition — including the Younger Dryas — which fragmented habitats faster than large, slow-breeding species could adapt. Modern research increasingly favours a combination whose balance varied by region and taxon, with humans and climate acting together. The debate matters far beyond prehistory: it informs present-day understanding of extinction risk, trophic cascades and rewilding, and frames whether humans were drivers of biodiversity loss tens of thousands of years before industrial society.

Related environment & climate events

• The Pleistocene–Holocene boundary and the start of the Holocene
  c. 11,700 years ago (c. 9700 BCE)
• End of the African Humid Period and Desertification of the Sahara
  c. 3500–2700 BCE
• The 8.2-kiloyear abrupt cooling event
  c. 6200 BCE
• The Last Glacial Maximum and human refugia
  c. 26,500 – 19,000 years ago
• The Toba super-eruption and the disputed 'volcanic winter'
  c. 74,000 years ago
• The Younger Dryas cold reversal
  c. 12,900 – 11,700 years ago

Further reading

A New Green History of the World

The wider story

A New Green History of the World

Clive Ponting

The classic accessible account of how environment and climate have shaped human history.

Get it on Amazon →

As an Amazon Associate, Human Saga earns from qualifying purchases.