They were hunted to extinction by the Native Americans.

unisci.com

Did Humans Cause Extinctions? Archaeologist Says No

The overkill hypothesis was proposed by retired University of Arizona ecologist Paul Martin in 1967 and its basic arguments haven't changed since.

Wikipedia

Pleistocene megafauna - Wikipedia, the free encyclopedia

Four theories have been given for these extinctions: hunting by the spreading humans, climatic change, spreading disease, and an impact from an asteroid or comet.

Discovery Channel

Climate Not Culprit of Megafauna Extinction : Discovery News

The appetites and activities of humans streaming into the continent across a land bridge from Asia provide another possible culprit.

Climate Not Culprit of Megafauna Extinction : Discovery News

As a result, it's looking more and more like humans played a major role.

Paul S. Martin (paleontologist)

Blame North America Megafauna Extinction On Climate Change, Not Human Ancestors

The overkill hypothesis was proposed by retired University of Arizona ecologist Paul Martin in 1967 and its basic arguments haven't changed since.

What Became of the Megafauna? » American Scientist

In Twilight of the Mammoths: Ice Age Extinctions and the Rewilding of America, Paul S. Martin reviews the end-Pleistocene extinction, arguing that overkill is the more likely explanation.

the mass extinction of the North American megafauna in the late Pleistocene@Everything2.com

Martin's theory is that humans were directly responsible for the mass extinction in the Late Pleistocene due to over hunting.

Gary Haynes (Univ. of Nevada Reno)

NOVA | End of the Big Beasts

Archeologist Gary Haynes, University of Nevada Reno, and others think that the continent's first human hunters, fresh from Siberia, killed the megafauna off as they colonized the newly discovered land.

actionbioscience.org

Mammoths: Resurrecting Extinct Megafauna (ActionBioscience)

A very different perspective, at least from the view of a North American, is shown by the following analogy: It can be demonstrated that humans had a hand in the North American extinction of the mammoths (and possibly other Pleistocene megafauna).

Mammoths: Resurrecting Extinct Megafauna (ActionBioscience)

There is compelling evidence that humans had a role in mammoth extinction, at least in North America.

Rewilding Megafauna: Lions and Camels in North America? (ActionBioscience)

The majority view in mainstream science now is that humans were the main cause of the extinction of these large animals, called megafauna.

Mammoths: Resurrecting Extinct Megafauna (ActionBioscience)

There is compelling evidence that humans had a role in mammoth extinction, at least in North America.

everything2.com

the mass extinction of the North American megafauna in the late Pleistocene@Everything2.com

Conclusion The mostly likely cause of the mass extinctions in North America at the end of the Pleistocene is a combination of both environmental cause and overkill.

About.com

Megafauna Extinctions - What were the Megafauna Extinctions

The mass extinctions were not synchronous nor universal, and the reasons proffered for them include (but are not limited to) climate change and human intervention.

cpluhna.nau.edu

Pleistocene Megafauna Extinctions on the Colorado Plateau

An opposing camp, pointing out that the extinctions closely followed the animals' first contact with modern humans, holds that the megafauna were essentially hunted to extinction.

highbeam.com

Spores tell tale of megafauna's disappearance: dung fungus finds ...

As a result, it's looking more and more like humans played a major role.

eurekalert.org

Blame North America megafauna extinction on climate change, not ...

The overkill hypothesis was proposed by retired University of Arizona ecologist Paul Martin in 1967 and its basic arguments haven't changed since.

trussel.com

Megafauna extinction mystery

One long-popular theory holds that the Clovis people, Stone Age immigrants from Asia who appeared in North America about 11,000 years ago, swept across the continent and hunted most of its large mammals to extinction.

slideshare.net

Lessons2and3thelittleiceage climate and change Edexcel Geography ...

ARCHEOLOGIST GARY HAYNES, UNIVERSITY OF NEVADA RENO, AND OTHERS THINK THAT THE CONTINENT'S FIRST HUMAN HUNTERS, FRESH FROM SIBERIA, KILLED THE MEGAFAUNA OFF AS THEY COLONIZED THE NEWLY DISCOVERED LAND.

goliath.ecnext.com

Spores tell tale of megafauna's disappearance: dung fungus finds ...

As a result, it's looking more and more like humans played a major role.

outriderbooks.com

woolly mammoth extinction out there science report at outrider

The overkill hypothesis was proposed by retired University of Arizona ecologist Paul Martin in 1967 and its basic arguments haven't changed since.

musmusmreading.blogspot.com

musmusmreading.blogspot.com

Archeologist Gary Haynes, University of Nevada Reno, and others think that the continent's first human hunters, fresh from Siberia, killed the megafauna off as they colonized the newly discovered land.

Disease.

New York Times

Disease Is New Suspect in Ancient Extinctions

It is simply too much to believe that ''a few thousand Indian men with pointed sticks could run around a continent and bring to extinction 135 species in maybe 400 years,'' said Dr. Ross D. E. MacPhee, a mammalogist at the American Museum of Natural History in New York, who advances the new disease hypothesis.

Disease Is New Suspect in Ancient Extinctions

Scientists who find neither the climatic nor the blitzkrieg theory convincing argue that rampant disease was the main villain.

Wikipedia

Pleistocene megafauna - Wikipedia, the free encyclopedia

Four theories have been given for these extinctions: hunting by the spreading humans, climatic change, spreading disease, and an impact from an asteroid or comet.

everything2.com

the mass extinction of the North American megafauna in the late Pleistocene@Everything2.com

Hyperdisease Theory The most recent development in the search for a cause has been that of the hyperdisease theory.

Preston A. Marx (virologist)

Pleistocene Megafauna Extinctions on the Colorado Plateau

The disease hypothesis, worked out by Dr. MacPhee and Dr. Preston A. Marx, a virologist at the Aaron Diamond AIDS Research Center in New York, holds that the animals were infected by lethal pathogens unknown to their immune systems.

Ross D.E. MacPhee (American Museum of Natural History)

NOVA | End of the Big Beasts

Mammalogist Ross MacPhee of the American Museum of Natural History has advanced the idea, with virologist Preston Marx, that a virulent "hyperdisease" brought by the first Americans might have raced through species with no natural immunity, bringing about their demise.

Megafauna extinction mystery

Instead, MacPhee is betting that a virus or other microbe new to the Americas arrived with human settlers and killed off many mammal species that had no natural resistance.

Pleistocene Megafauna Extinctions on the Colorado Plateau

It is simply too much to believe that "a few thousand Indian men with pointed sticks could run around a continent and bring to extinction 135 species in maybe 400 years," said Dr. Ross D.E. MacPhee, a mammalogist at the American Museum of Natural History in New York, who advances the new disease hypothesis.

cpluhna.nau.edu

Pleistocene Megafauna Extinctions on the Colorado Plateau

Scientists who find neither the climatic nor the blitzkrieg theory convincing argue that rampant disease was the main villain.

Pleistocene Megafauna Extinctions on the Colorado Plateau

Scientists who find neither the climatic nor the blitzkrieg theory convincing argue that rampant disease was the main villain.

trussel.com

Megafauna extinction mystery

Another scenario casts human immigrants (or perhaps animals or insects they brought with them) as unwitting deliverers of a killer virus that devastated the continent's wildlife.

mcdaniel.edu

The Grasslands of the US - McDaniel College

Scientists who find neither the climatic nor the blitzkrieg theory convincing argue that rampant disease was the main villain.

musmusmreading.blogspot.com

musmusmreading.blogspot.com

Mammalogist Ross MacPhee of the American Museum of Natural History has advanced the idea, with virologist Preston Marx, that a virulent "hyperdisease" brought by the first Americans might have raced through species with no natural immunity, bringing about their demise.

Climate change.

Wikipedia

Pleistocene megafauna - Wikipedia, the free encyclopedia

Four theories have been given for these extinctions: hunting by the spreading humans, climatic change, spreading disease, and an impact from an asteroid or comet.

Discovery Channel

Climate Not Culprit of Megafauna Extinction : Discovery News

Researchers have long debated what triggered the extinctions that struck North American megafauna between 14,000 and 11,000 years ago (SN: 12/4/99, p. 360), and one of the prime candidates has been habitat change caused by a warming climate.

everything2.com

the mass extinction of the North American megafauna in the late Pleistocene@Everything2.com

Environmental Cause Theory The first suspect in the search was the changing environmental conditions occurring in North America, and around the world, about 11,000 years ago.

About.com

Megafauna Extinctions - What were the Megafauna Extinctions

The mass extinctions were not synchronous nor universal, and the reasons proffered for them include (but are not limited to) climate change and human intervention.

Russell W. Graham (Denver Museum of Natural History)

Pleistocene Megafauna Extinctions on the Colorado Plateau

In this hypothesis, advocated by Dr. Russell W. Graham of the Denver Museum of Natural History among others, North America in the earlier Pleistocene was dotted shore to shore by different habitats, each favorable to particular species.

cpluhna.nau.edu

Pleistocene Megafauna Extinctions on the Colorado Plateau

Those who subscribe to the climate-change theory of the extinctions argue that the driving force behind them was the destruction of habitat brought about by oscillating periods of warmth and cold during the Pleistocene era, the era of on-and-off glaciation that began about a million years ago.

Pleistocene Megafauna Extinctions on the Colorado Plateau

One camp in the debate contends that a rapidly changing climate at the end of the last ice age did in the Pleistocene megafauna, as they are called, by transforming their habitat.

Pleistocene Megafauna Extinctions on the Colorado Plateau

Those who subscribe to the climate-change theory of the extinctions argue that the driving force behind them was the destruction of habitat brought about by oscillating periods of warmth and cold during the Pleistocene era, the era of on-and-off glaciation that began about a million years ago.

Donald Grayson (Univ. of Washington)

Blame North America Megafauna Extinction On Climate Change, Not Human Ancestors

Grayson points to climate shifts, during the late Pleistocene epoch, which ended about 10,000 years ago, and subsequent changes in weather and plants as the likely culprits in the demise of North America's megafauna.

NOVA | End of the Big Beasts

Donald Grayson, an archeologist at the University of Washington, Seattle, along with colleague David Meltzer of Southern Methodist University, believes that climate changes at the end of the Pleistocene epoch triggered the collapse.

trussel.com

Megafauna extinction mystery

According to one view, rapid climate shifts at the end of the Ice Age altered the pattern of North American vegetation, shrinking the habitats of the big mammals until they became extinct.

A meteor impact.

Wikipedia

Pleistocene megafauna - Wikipedia, the free encyclopedia

Four theories have been given for these extinctions: hunting by the spreading humans, climatic change, spreading disease, and an impact from an asteroid or comet.

James Kennett (Univ. of California Santa Barbara)

NOVA | End of the Big Beasts

And, in the newest hypothesis advanced, geologist James Kennett, U.C. Santa Barbara, and colleagues propose that a comet impact or airburst over North America did it.

A supernova blasted them with gamma radiation.

Independent (UK newspaper)

The end of the world as we know it - Science, News - The Independent

The demise of large North American mammals 41, 000 years ago has been linked to a supernova, and several other mini-extinctions may be tied to the cataclysm of stellar death.