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.
Common sense will win a war over scientific evaluation. Matter of fact, the war would be long over before the scientific solution were agreed upon by the elitists.
As any good hunter knows, buffalo jerky can be found at your nearest gun show...
A good deal of the central plains was actually woodland at the time.. At least that south of the glacial lakes..
When the glacial dams ( I think they were called Morains ) broke under the pressure, great floods swept south destroying much of those woodlands..
They weren't that heavy, but much more forested than the plains of today..
Those woodlands provided cover for predators, allowing them to close in on their prey before a quick, rushing attack to dispatch the prey..
Additionally the glacial lakes would have been fairly heavily forested along the shorelines..
In fact, as the glacial melt began, water levels would have risen right into the surrounding forestlands..
Big Cats especially, do a great deal of their hunting along the shores and banks of "watering holes"..
That is where the meat is..
Big predators need big protein..
Open plains mean plenty of running room for buffalo, antelope, etc..
Running down prey on an open plain requires even more protein..
Somewhere along the line, you find a point of no return, benefit less than effort required..
End result: Starvation..
I think you are essentially correct, but the actual emergence of wide open plains actually occurred at the end of the Ice age as well as all those other factors..
Climate change, (warming) glacial melt causing flooding, ( Mega Flash Floods ) The sudden loss of possibly thousands of small lakes and of course, the big glacial lakes, the loss of grazing land scoured by the floods, probably the deaths of millions of herbivores as well as thousands of carnivores..
All these factors would have contributed to the loss of not only mega fauna but taken a major chunk out of any other animal or human inhabitants throughout the Midwest, upper midwest, the northwest, large chunks of mid-southern Canada, etc...( Not positive about the eastern continent, but I seem to recall much of the same flooding, etc. took place there as well..
The arrival of a large number of new human inhabitants would have eventually contributed as well, ( I believe there were other, earlier, smaller groups scattered about along the east and gulf coast, as well as central and south american coast ) but I believe much of the "damage" was natural..
As others have pointed out, I don't think there were enough humans here at that point to have had that much effect on ALL of the Mega Fauna of America..
Just doesn't make sense..
Thanks for the tip! I'll take my boys with me...it should be a lot of fun.
No comment other than the fact that the grants that paid for this study were a waste of cash.
"And they were 100% wrong."
I must have missed their retraction. So, that whole thing turned out to be bogus?
well, there ya have it. We global freeze, we global warm...seem evolution has really done a poor job by allowing us to proliferate so much.
That's okay. We still have cows.
I think the main hole in their theory is that there is irrefutable proof that the Clovis First Theory is dead.
Unless they can come up with something better than a Clovis point as an indication of a new factor around 11,000 years ago, this theory holds no water - not even ice.
Why did man live here for over 30,000 years without eating into extinction all the ice age megafauna, and then all of a sudden, 11,000 years ago wipe them out??
Some cultural change?? New "invaders"?
Lots more than guns at Gun Shows..
Found a great refractor telescope there, cheap.. also binoculars.. In the late summer and fall, there are all sorts of hunting jackets, other gear, tons of knives, and kitchen-dining room cutlery, tools of all sorts, ( magnifiers, tweezers, "extra hands", vices, grinders ) exotic woods ( pick your project, not just for knife handles ) and other oddball stuff..
And of course, there are guns, but often you will find historical exhibits as well..
Civil War weapons, complete with photos of the military units that used them..
Historical western gear, used by cowboys, sherriffs, outlaws, you name it.. again, often accompanied by photos, sherrriff's badges, other documents..
There can also be WW1, WW2 memorabilia, from all the military branches, and tons of books recounting various military operations from Sicily to Iwo Jima..
Throughout, you will find Men and Women that are dedicated to America, Patriotism, and the 2nd amendment..
A good message and example for young men..
Have a good time..
It's Bush's fault. He should be forced apologize and explain why this had to happen.
Just one small problem, though. Humans were on the North American Continent long before the Clovis types which are generally dated ca 12,000 years ago. Seems they would have gnawed the last of the big critters before Clovis or Folsum cultures got their spears sharpened...
Ordinary climate change and diminishing habitat got the megafauna, and climate has been changing and will continue to change regardless of humans actions short of full tilt nuclear war. I really doubt we have that much global influence.
Most of this crap was started as a Communist Bloc effort (their seed money plus a lot of useful idiots) to shut down West Bloc industry during the Cold War.
Nasty little pygmies eating thunder lizard omlettes.....
Not until the horse (nasty white guy innovation) did the hunt become more efficient, just because they could take individual animals instead of killing them wholesale.
Maybe 11,000 years ago they invented the chilli cook-off?
those cavemen drove SUVs ?
.......Solid evidence that Europeans arrived in America long before Columbus.
HE was killing all those creatures and burying them in shale so he could reap oil profits 11,000 years later!
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