Extraterrestrial impact killed megafauna

New evidence that extraterrestrial impact killed off the mammoths

By Thomas H. Maugh IIMelted glass buried deep within the Earth at sites around the world confirms the theory that a comet or meteor struck the planet nearly 13,000 years ago, triggering the Younger Dryas Ice Age, killing off the mammoths and other megafauna in North America, and perhaps even causing the disappearance of the Clovis culture of early Native Americans. The cause of the Younger Dryas cooling period has been very controversial. Some researchers have proposed an extraterrestrial impact and have produced evidence of the event, but others claim that the results have not been replicated. The new findings, reported this week in the Proceedings of the National Academy of Sciences, appear to provide that needed replication.

The Younger Dryas event began about 12,900 years ago and lasted about 1,300 years. The period is named after the alpine-tundra wildflower, Dryas octopetala, which spread southward during the period. Average temperatures during the period dropped by as much as 20 degrees Fahrenheit in Europe, perhaps a little less in North America. The period marked the end of the mammoths, giant ground sloths and other large creatures that had earlier wandered North America. Artifacts from the Clovis culture, whose members are believed to be among the earliest settlers of this continent, disappeared from the archaeological record. Northern glaciers moved southward and forests turned into tundra. The period is linked to the onset of agriculture in the Middle East, perhaps because hunting and gathering could no longer provide adequate food supplies.Another report says the megafauna began dying during the last major ice age. Then the minor Younger Dryas Ice Age finished them off.

Humans Did Not Kill Off Mammoths; Comet, Climate Change Helped, Studies ShowAlthough human hunting played a part in the demise of the woolly mammoth about 10,000 years ago, homo sapiens were but bit players in a global drama involving climate change, comet impact and a multitude of other factors, scientists have found in separate studies.

Previous research had blamed their demise on tribal hunting. But new findings “pretty much dispel the idea of any one factor, any one event, as dooming the mammoths,” said Glen MacDonald, a researcher and geographer at the University of California in Los Angeles, to LiveScience.com.

In other words, hunting didn’t help, but it was not instrumental. The ancestors didn’t do it.

So what did? After thriving for 250,000 years, the huge mammals lingered on in dwarf form in the Arctic Ocean’s Wrangel Island until 3,700 years ago. Between 20,000 and 25,000 years ago, LiveScience said, the animals declined during the worst of the last major ice age, though they started to multiply in warmer interior Siberia.

Analyzing samples from more than 1,300 woolly mammoths as well as 450 pieces of wood, 600 archeological sites and upwards of 650 bog lands in Beringia—the former land bridge under the Bering Strait, thought to be the giant mammoths’ last habitat—a team led by MacDonald discovered a host of things working against them.

The beasts were felled by a combination of declining food supply and terrain that deteriorated into peatlands, all brought on by warming climate, said the study as quoted in USA Today. Grasses and willow, mammoths’ normal food, was replaced by poisonous birch to eat, and solid ground gave way to wetlands more difficult to tread upon, USA Today said.

“Pressure from hunting was also present, as contemporary Paleolithic sites are numerous in both Siberia and now in northwestern North America,” the study said. “Modeling studies show that given the environmental stresses at the time, even limited hunting by humans could have significantly contributed to woolly mammoth extinction.”I watched an episode of NOVA last year that covered this subject too.

Megabeasts' Sudden DeathScientists propose a radical new idea of what killed off mammoths and other large animals at the end of the Ice Age. Aired March 31, 2009 on PBS.

Program Description

Fifteen thousand years ago, North America was like the Serengeti on steroids, with mega-creatures roaming a continent teeming with incredible wildlife. But then, in a blip of geologic time, between 15 and 35 magnificent large types of animals went extinct. In this television exclusive, NOVA joins forces with prominent scientists to test a startling hypothesis that may finally explain these sudden and widespread extinctions—that a comet broke apart in the atmosphere and devastated North America 12,900 years ago.The program discusses the conventional wisdom. You know, that the Paleo-Indians were so brutal, bloodthirsty, and unconcerned with ecological balance that they slaughtered the animals to extinction. Here's the transcript on that point:JAMES KING: Man probably came to North America at that point as a super-predator with a naïve fauna that had no idea what they were facing. The super-predator had communication, it had weapons, it hunted in groups, it had coordination, it had all the things you would do if you and I were going out to try and hunt big animals.

NARRATOR: More recent history supports this theory. In Mauritius, the arrival of the Dutch doomed the dodo, and in New Zealand, the first settlers killed off the moa. But could this also have happened to these great animals all across North America?

JAMES KENNETT: The data just doesn't support this. It's inconceivable to me.

NARRATOR: Kennett says the idea that primitive humans killed off these powerful animals is absurd, and while it might happen in small island environments, it is impossible to imagine they could wreak such havoc on a continent as vast as North America.

JAMES KENNETT: They didn't have the technology that modern humans have. They didn't have helicopters and machine guns and satellite navigation and so forth. It's always puzzled me. How could they track down that last horse or that last mammoth or that last camel? It just perplexed me. It just didn't make sense.Comment:  It's not clear whether the comet or meteor did most of the killing or just completed the killing. What's clear is that humans played only a minor role. They probably did a "normal" amount of killing for their technology and population levels. They didn't kill everything in sight because they were murderous savages aka "super-predators."

This doesn't seem like rocket science to me. The earth experienced a series of ice ages followed by warming periods, which shocked the flora and fauna repeatedly. To top it off, a comet crashed into the earth and caused rapid, large-scale climate change. With all this disruption, you don't need humans to explain the megafauna extinction.

What about all those scientists who stuck to their super-predator theory--who refused to consider a climate-change alternative? How much of their thinking was influenced by the idea of (Paleo-)Indians as murderous savages? A lot, I suspect. It's something every schoolchild learns by rote: that Indians excel at killing.

For more on the subject, see Clovis First Theory Disproved and Ecosystem Disruption Killed Megafauna?