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Humans to Blame for Ice Age Extinctions, Study Says
National Geographic ^ | August 10, 2005 | Hillery Mayell

Posted on 08/11/2005 11:02:22 AM PDT by ZULU

Humans are likely responsible for the extinction of Ice Age megafauna—large mammals like giant sloths, short-faced bears, mammoths, and saber-toothed cats—that occurred in the Americas around 11,000 years ago, a new study says.

Scientists have long debated whether giant pre-historic mammals disappeared because of climate change or because humans hunted them to extinction.

The mass extinctions coincided with both the end of the last Ice Age and the arrival of humans in the Americas around 11,000 years ago. This timing has made it difficult for scientists to isolate the cause of the species' disappearance.

But a study comparing the extinction of giant ground sloths in North and South America with the disappearance of their smaller relatives in West Indian islands has helped clear up the picture, scientists say.

The researchers say archaeological and fossil evidence strongly suggests that ancient hunters pushed the animals to extinction.

Giant ground sloths "cruised through" at least 22 major climate cycles as the continental ice sheets in North America advanced and retreated over the last two million years, said David Steadman, a paleobiologist at the University of Florida.

Steadman is a co-author of the new study published in the Proceedings of the National Academy of Sciences.

"The only thing that's different [at the end of the Ice Age] is the arrival of people," he said.

Giant Sloth: A Case Study

Until about 11,000 years ago, at least 19 different sloth species lived in North and South America in a variety of ecosystems. Only a few small, tree-dwelling sloth species survive today.

Steadman and his colleagues argue that if ecosystem shifts resulting from climate change caused the sloths' demise, then all extinctions—on both islands and the mainland—should have taken place at the same time, as the last Ice Age ended between 15,000 to 9,000 years ago.

Radiocarbon dates of bones, dung, and other tissue of extinct sloths place their last appearance in North America at around 11,000 years ago and at about 10,500 years ago in South America, Steadman says.

But on the islands of Cuba and Hispaniola—shared today by modern-day Haiti and the Dominican Republic—sloths survived until about 4,400 years ago.

Their subsequent extinction coincided exactly with the arrival of the first humans on the islands, Steadman says.

"What [this study] shows us is that there's this great big suggestive pattern that we find: Wherever human beings first appear all around the world, these large mammals pretty quickly become extinct," said Gary Haynes, an archaeologist at the University of Nevada at Reno, who was not involved in the study.

"[Some] people will say that you have to [establish the cause of extinction] species by species, and I think they're probably right," Haynes added. "But the study does create a good model that might make us think that if it worked for one big animal it's probably what we'll find for other big animals."

Overkill Vs. Climate Change

Steadman and his colleagues argue that megafauna species on the American continents, having evolved in an environment without humans, may have been particularly vulnerable to the sudden appearance of big game hunters.

The 5,000-pound (2,300-kilogram) giant ground sloth is a case in point. In addition to having no fear of humans, it was the size of a modern-day elephant, it couldn't hide, and as it name implies, it moved very slowly.

"Walking up to a ground sloth and trying to spear it to death probably wasn't one of the most macho things they [early hunters] did," Steadman said. "Any hunter could outrun one."

But other scientists maintain that climate change was the driving force in Ice Age extinctions. They argue that the retreat of ice sheets from North America caused a major change in habitat that the giant mammals couldn't adapt to.

At the peak of the Ice Age around 20,000 years ago, the ice covered much of North America.

As the sheets melted between 18,000 and 8,000 years ago, warmer temperatures and shifting rainfall patterns forced plants and animals to move out of old habitats and into new ones.

Proponents of the climate-change theory add that there's little evidence that humans hunted anything other than mammoths. Yet species like wild horses, camels, and saber-toothed cats all went extinct at about the same time.

"There are no archaeological sites for species other than mammoths, and perhaps mastodons, where you find a spear sticking out of an animal, and everyone agrees that there is evidence of human hunting," Nevada's Haynes said.

"So the lack of kill sites doesn't bother me," he added. "There's a real lack of a 'smoking gun' implicating either climate change or human hunting, but that's true for every theory."

Climate change may have been a factor in pushing the animals to extinction, Steadman says, but it took humans to push them over the edge.

"Animals like the ground sloth, which had a poor ability to regulate body temperature, should have thrived in a warmer climate," he said.


TOPICS: Culture/Society
KEYWORDS: bushsfault; catastrophism; culinaryarts; godsgravesglyphs; history; moronscience; powerfuldelusion; revisionistscience
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To: Boundless
And we won't even bring up Easter Island prior to whitey.

Don't. It's ugly. You've read 'Collapse'?

41 posted on 08/11/2005 11:27:23 AM PDT by Right Wing Professor (Proudly neocon since 1982!)
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To: Right Wing Professor

42 posted on 08/11/2005 11:27:48 AM PDT by mewzilla (Property must be secured or liberty cannot exist. John Adams)
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To: ZULU

I wonder whether these "native americans" had the chance to read Al Gore's book on global warming.

Certainly, they ended the ice age, what with their campfires and methane farts from eating so much mammoth fur, so early man must have been responsible for the early global warming.


43 posted on 08/11/2005 11:28:10 AM PDT by aShepard
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To: mewzilla
ROFL!

Good thing they weren't smart enough to develop insecticides...er, I guess those would have been 'homicides'.

44 posted on 08/11/2005 11:30:15 AM PDT by Right Wing Professor (Proudly neocon since 1982!)
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To: ZULU
The mass extinctions coincided with both the end of the last Ice Age and the arrival of humans in the Americas around 11,000 years ago. This timing has made it difficult for scientists to isolate the cause of the species' disappearance.

Another huge embarrassment for National Geographic coming...

Remember when they "proved" that we were all descended from one African female? Cornrows and all? I'm sure they's rather not talk about it.
They had it nailed beyond any challenge whatsoever.
And they were 100% wrong.

45 posted on 08/11/2005 11:30:18 AM PDT by Publius6961 (Liberal level playing field: If the Islamics win we are their slaves..if we win they are our equals.)
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To: ZULU

Bushstone's Fault!!


46 posted on 08/11/2005 11:31:16 AM PDT by hispanarepublicana (There will be no bad talk or loud talk in this place. CB Stubblefield.)
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To: Right Wing Professor
Good thing they weren't smart enough to develop insecticides...er, I guess those would have been 'homicides'.

LOL!! I can just see it now. Okay, who's got the Cro Magnon repellent?

47 posted on 08/11/2005 11:32:50 AM PDT by mewzilla (Property must be secured or liberty cannot exist. John Adams)
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To: ZULU

Is it wrong that the most upsetting part of this whole thing (to me) is that I'll never get to know what giant sloth or wooly mammoth taste like with Stubbs BBQ sauce?


48 posted on 08/11/2005 11:33:02 AM PDT by leoncaruthers
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To: ZULU

If only PETA had been around 11,000 years ago, then no doubt the woolly mammoths would still be here today.


49 posted on 08/11/2005 11:34:24 AM PDT by jpl
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To: ZULU

It was Bush's great-great-great-great-grandparents fault!


50 posted on 08/11/2005 11:35:57 AM PDT by Stark_GOP
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To: Publius6961
Remember when they "proved" that we were all descended from one African female? Cornrows and all? I'm sure they's rather not talk about it.

I don't see why not. It's not even controversial. It's a simple mathematical fact that at some point in the not-too-distant past we are all descended matrilineally from a single person.

51 posted on 08/11/2005 11:38:31 AM PDT by Right Wing Professor (Proudly neocon since 1982!)
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To: ZULU
This timing has made it difficult for scientists to isolate the cause of the species' disappearance.

Perhaps prehistoric humans took their drinks "on the rocks" and depleted the planet of it's ice reserves?

52 posted on 08/11/2005 11:38:43 AM PDT by EGPWS
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To: ZULU
poppycock




Doogle
53 posted on 08/11/2005 11:41:10 AM PDT by Doogle (8th AF...4077thTFW....408MMS....Ubon Thailand "69"..Night Line Delivery ..AMMO)
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To: jpl

No, Peta would have killed them off and stuffed them in dumpters


54 posted on 08/11/2005 11:44:48 AM PDT by Nathan Zachary
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To: leoncaruthers
Is it wrong that the most upsetting part of this whole thing (to me) is that I'll never get to know what giant sloth or wooly mammoth taste like with Stubbs BBQ sauce?


Giant Sloth taste like chicken>

55 posted on 08/11/2005 11:45:30 AM PDT by CIB-173RDABN
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To: ZULU

PETA = People Eating Tasty Animals


56 posted on 08/11/2005 11:46:00 AM PDT by PeteB570
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To: ZULU

It was the SUVs!


57 posted on 08/11/2005 11:49:32 AM PDT by BenLurkin (O beautiful for patriot dream - that sees beyond the years)
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To: Night Hides Not

she was of child bearing age, which is why cave men were so darned UGLY.


58 posted on 08/11/2005 11:50:27 AM PDT by absolootezer0 ("My God, why have you forsaken us.. no wait, its the liberals that have forsaken you... my bad")
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To: gate2wire

Bush lied, sloths died.


59 posted on 08/11/2005 11:51:30 AM PDT by TC Rider (The United States Constitution 1791. All Rights Reserved.)
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To: ZULU

It's the "Native-Americans" fault! You know, the ones who everybody says were sensivtive to the environment. What is PETA doing to condemn them?


60 posted on 08/11/2005 11:52:24 AM PDT by Humvee
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