Megafaunal extinctions – that is to say the massive die-off of huge numbers of species of large bodied mammals – occurred in every location on the planet at or about the same time as humans arrive there, and at the same time as climate change occurred. Whether the extinctions resulted from climate change or human predation; or climate change drove human migrations and animal die off: or animal die off forced people to migrate two new places as not been established.
This page describes the evidence for massive, large animal extinctions that co-occurred with the human occupation of North and South America.
North America's Mass Extinctions
- Earliest human colonization to date: 15,000 calendar years ago (cal BP), (pre-Clovis sites.
- Last glacial maximum: ~30,000-14,000 cal BP
- Younger Dryas: 12,900 to 11,550 cal BP
- Biomass burning: widespread, identified as "black mat"
- Important sites: Rancho La Brea (California, USA), many Clovis and pre-Clovis sites.
- Die off range: 15% disappeared during Clovis and the Younger Dryas overlap, 13.8-11.4 cal BP
- Species: ~35, 72% of mega fauna, dire wolf (Canis dirus), coyotes (C. latrans), and saber-toothed cats (Smilodon fatalis); American lion, short-faced bear (Arctodus simus), brown bear (Ursus arctos), scimitar-tooth sabercat (Homotherium serum), and dhole (Cuon alpinus)
While the exact date is still under discussion, it is most likely that humans first arrived in North America no later than about 15,000 years ago, and perhaps as long ago as 20,000 years ago, at the end of the last glacial maximum, when entrance into the Americas from Berengia became feasible. The continents were rapidly colonized, with populations settled in Chile by 14,500, surely within a few hundred years of the first entry into the Americas.
North America lost about 35 genera of mostly large animals during the late Pleistocene, accounting for perhaps 50% of all mammal species larger than 32 kilograms (70 pounds), and all species larger than 1,000 kg (2200 lbs). The ground sloth, American lion, dire wolf, and short-faced bear, woolly mammoth, mastodon and Glyptotherium (a large bodied armadillo) all disappeared. At the same time 19 genera of birds disappeared; and some animals and birds made radical changes in their habitats, permanently changing their migration patterns. Based on pollen studies, plant distributions also saw a radical change primarily between 13 to 10,000 calendar years ago (cal BP). increased evidence of biomass burning.
Between 15,000 and 10,000 years ago, biomass burning gradually increased, particularly at the movements of rapid climate change at 13.9, 13.2, and 11.7 thousand years ago. These changes are not currently identified with specific changes in human population density or with timing of the megafaunal extinction. A cometary impact has been hypothesized to have occurred over the Canadian Shield at about 12.9 thousand years ago, igniting continent-wide wildfires. However, evidence for this event (also known as the black mat theory) is inconclusive and widely contested, and it is unclear that continent wide wildfires ever occurred at the beginning of the Younger Dryas.
South America's Mass Extinctions
Less scholarly research concerning the mass extinctions in South America has been published, at least in the English-language academic press. However, recent investigations suggest that the extinction intensity and timing varied across the South American continent, beginning in the North latitudes several thousand years before human occupations, but becoming more intense and rapid in the southern higher latitudes, after humans arrived. further, according to Barnosky and Lindsay, the pace of extinction seems to have accelerated about 1000 years after the humans arrived, but coinciding with regional cold reversals, the South American equivalent of Younger Dryas.
- Earliest human colonization to date: 14,500 cal BP (Monte Verde, Chile)
- Last glacial maximum: 12,500-11,800 cal BP, in Patagonia
- Cold Reversal (Roughly equivalent to the Younger Dryas): 15,500-11,800 cal BP (Varies across the continent)
- Biomass burning:
- Important sites: Lapa da Escrivânia 5(Brazil), Campo La Borde (Argentina), Monte Verde (Chile), Pedra Pintada (Brazil), Cueva del Milodón (Patagonia)
- Date of most extinctions: 18,000 to 11,000 cal BP
- Species:52 genera or 83% of all megafauna; Holmesina, Glyptodon, Haplomastodon, prior to human colonization; Cuvieronius, Glossotherium, Equus, Hippidion, Mylodon, Eremotherium and Toxodon about 1,000 years after initial human colonization; Smilodon, Catonyx, Megatherium, and Doedicurus, late Holocene
Recently, evidence of the survival of several species of giant ground sloth has been discovered in the West Indies, to as late as 5,000 years ago, coincident with the arrival of humans in the region.