The Big Debate

[MarkGelbart]

Here's my model of Pleistocene megafauna extinction based on the latest scientific findings.

Grizzly bear fossils in North America date to about 30,000 years before present and apparently they migrated here from Asia. This indicates there was quality land some where near the western glacier that could have supported a human population. Humans spread through this early corridor. There is scant but compelling archaeological evidence in North America of man before the Clovis culture appears at Cactus Hill, the Topper site, and a few other sites.

The early pioneers of North America were general foragers who also hunted big game such as mammoths and mastodons. But about 13,000 years ago they became more efficient killers of big game. Perhaps this is when someone invented the atlatl or throwing spear, and they also began manufacturing the big arrow heads recognizable as the Clovis culture.

The Clovis culture remained general foragers living on big and small game, fish, and plants, but they began killing just slightly more big game animals than they did previously. According to Alroy (Alroy 2001), even low levels of hunting pressure could have caused the extinction of large slow-reproducing mammals.

In 500-1000 years as the Clovis culture spread, the paleo-Indians wiped out the giant ground sloths, mammoths, and mastodons. This in turn was catastrophic to the entire ecosystem. In the east the forest canopy closed because the big animals no longer tore up and uprooted trees. This was devastating to grazers such as horse, bison, and llama populations which were also under pressure from increased human hunting. In addition scavenging condors and eagles died out.

Populations of humans were unaffected--they simply switched to other sources of protein.

My model completely excludes climate change as a factor. In fact every single scientific paper I've ever read that considers climate change as the main factor in megafauna extinction is remarkably illogical. Some (see Grayson and Meltzer) are just plain bad studies.

My model accounts for the existence of a pre-Clovis culture and explains how human populations could have been high enough to impact the wildlife. There already was a population of humans here that became more technologically efficient hunters.

[ashcraft]

Problems for you to consider- why didn't the bison go extinct? Some did, but they were a common group from coast to caost when the Europeans arrived for the 3rd time, at least. Why didn't the pachyderms go extinct in Africa and Asia, where they have dealt with man for much longer? Why did the grizzlies, wolves and mountain lions not go extinct, while other major predators did?

There is considerable evidence for major climatic change around the same time, it could be coincidental to the extinctions. Look up hypsithermal event. We still have remnants of the vey arid conditions that existed at this time in Missouri, including cacti, yucca plants, scorpions, and tarantulas. They exist in fragmentary areas where they can compete with our more normal temperate plants, such as glades and sand prairies.

Brent Ashcraft

[Guest N.AL.hunter]

There is no doubt that the climate did change around the time of the mega-fauna extinctions. We know this; since, we no longer have the entire northern part of the country under ice.

How does this sound: 1. As the climate warmed up the types of trees changed and the extent of forests increased.

2. The growing forested areas diminished the amount of grazing land available for the large herbivores.

3. This decreased their numbers directly and it also 'pushed' them toward the middle of the country where the grasslands were still vast.

4. Now they are concentrated into smaller areas where man could more easily hunt them.

5. Also, being more confined, they are more prone to disease.

6. The bison didn't go extinct because it was too mean (ha ha). No, the reason for the still existent grizzly, bison, mountain lion is one of lack of competition. Back then you had several species of bear, large cat, grazing critters... The stress was most likely great on all of them, but as one type became extinct, the pressure lifted a little on the remaining types. The ones that got a toe hold the fastest (modern mountain lion, grizzly, bison...), got the niche.

I most likely could go on, but that is probably enough of my BS knowledge for anyone.

[MarkGelbart]

Bison almost did become extinct. The Long-Horned bison became extinct but was replaced with the short-horned bison which survived as a relic in the sparsely populated great plains. The population of bison was probably pretty small during the recent Holocene until European diseases wiped out a large percentage of the American Indians. So the early European accounts of great bison herds might be deceiving. Bison were expanding their range because Indian populations were depeleted. Bison also reproduce just slightly more rapidly than horses, and they adapted better to human hunting strategies, running and becoming skittish rather than fighting aggressively with their horns like long-horned bison did.

Wolves were not often a direct food resource and could survive on deer which reproduce rapidly. White tailed deer for example reproduce 30,000 times more rapidly than African elephants.

Grizzly bears hibernate for part of the year and because they're hard to find, at least some of the time, they survived human predation.

Elephants and other big game survived in tropical regions because tropical diseases keep human populations low.

The climate during the megafauna extinction didn't change that much. The extinction occurred during the Younger Dryas cooling spell. The megafauna survived the Last Glacial Maximum a few thousand years before and in fact most species survived millions of years of climate oscillations. Nope, climate change doesn't come close to explaining it. Climate change as a cause of extinction implies the extinction of plants that the animals fed upon. Almost no species of plants became extinct.

[Guest Nicholas]

There is no doubt that the climate did change around the time of the mega-fauna extinctions. We know this; since, we no longer have the entire northern part of the country under ice.

How does this sound: 1. As the climate warmed up the types of trees changed and the extent of forests increased.

2. The growing forested areas diminished the amount of grazing land available for the large herbivores.

3. This decreased their numbers directly and it also 'pushed' them toward the middle of the country where the grasslands were still vast.

4. Now they are concentrated into smaller areas where man could more easily hunt them.

5. Also, being more confined, they are more prone to disease.

6. The bison didn't go extinct because it was too mean (ha ha). No, the reason for the still existent grizzly, bison, mountain lion is one of lack of competition. Back then you had several species of bear, large cat, grazing critters... The stress was most likely great on all of them, but as one type became extinct, the pressure lifted a little on the remaining types. The ones that got a toe hold the fastest (modern mountain lion, grizzly, bison...), got the niche.

I most likely could go on, but that is probably enough of my BS knowledge for anyone.

I tend to agree with you, the new landscapes seemed to be too much for larger herbivores. If they had more contact with each other than what would normally be acceptable the chances of them being wiped out by disease are quite increased, this happens in modern day moose for example. I think you've summed it up quite nicely for at least a more Southern North America perspective.

What about all those nice Canadian Mammoths, and Mastodon? Chances are that they more likely wiped out by human means then any where else on North America. The forests didn't grow as thick and there were still plenty (At least of what we think we know) to support large herbivores.

As for why other animals didn't die out by act of nature or human interference... I don't think anyone can tell you. I know that the Grizzly is considered to be one of the best adaptive animals, and a very good survivor. Perhaps that was enough.

[Guest N.AL.hunter]

"Almost no species of plants became extinct."

Extinction of the plants is not the issue. The climate change allowed for different species to take a larger role, but it did not force others to become extinct as much as become less. When an animal has evolved to eat/specialize in a food source, and that food source becomes less abundant, then the animal either adapts to new source or dies. I am not saying that climate alone caused the extinctions, because, as I stated, human hunting them and disease, probably all had something to do with it. However, to say that climate change had no influence, is not scientifically reasonable. Climate change places stress on creatures and plants. Those that are already living on the fringe could be pushed to extinction by the slightest climate change or driven to a lesser geographic range.

I have not made any study of this issue, but might now as my interest has been stimulated. I need to work out the timeline, and then formulate the truth, and publish it, and win the Nobel Prize. Stay tuned.

[Ramo]

As far as man hunting Mammoths to extenction, I remember reading something by someone (I know that's sounds like a prety good source) that went something like this. "A tribe of cavemen probably killed one or two mammoths in a lifetime ans spent the rest of their lives talking about it."

As small as the human population was in those days, and by using spears, atl-atls, and herding over cliffs, I just can't imagine that those early humans hunted very many mammoths. Just like with predators today, the risk to injury far outweighed the gain. Even a minor injury in those days probably ment death, and there were a lot easier animals to kill than mammoths back then.

[ashcraft]

Plants can all die out, and still not go extinct, its called seeds, which can remain viable for many years. Some were found in the great pyramids of egypt that would still germinate (certainly not all of them). It wouldn't ake long for mass starvation to occur, if only one growing season is lost, I suspect most large herbivores would die.

Bison and deer were both in a rapid speciation event, not due to the death of the American Indians, but due to the death of the Mega fauna, whose niches they were trying to fill.

The death of large numbers of American Indians by European disease has never been shown. It certainly is a possibility. Indian tribes were lost long before the Europeans arrived, including the Mayans, Anastazi, etc. There even is some evidence that the Mound Builders were gone before the Europeans arrived.

Many of the pachyderms are not found in the tropics, but have survived.

The ground sloths survived in cuba until the 1500's, horses appear to have survived in southern Alaska way past the megafauna extinction. Muskoxen have also survived, why not the wooly rhino or mastodon, both which appear to have been able to survive in extremly harsh cold environments.

The hypsithermal event, which started some 10,000 years ago was pretty significant, based on pollen studies. Large tracts of deciduous forests, which had recently converted from boreal forests, in the central US were converted to plains or to desert. Global warming in the exteme. Did the extinction event happen before this? Was it the final straw?

A very interesting event for sure.

Brent Ashcraft

[Boesse]

The issue as well is that Mammoths and other large vertebrates did not immediately go extinct in Europe when humans first arrived; in contrast to North America, there was a longer lag time between events. So... what happened in europe? Were ancient people in europe dumber than those in north america?

[Ramo]

Not just acient people Boesse. It still holds true today.

[Guest Nicholas]

Not just acient people Boesse. It still holds true today.

Ouch...

[MarkGelbart]

Na Hunter,

You're wrong. Extinction caused by climate change inherently means species of plants the megafauna ate must have become extinct.

Actually, we do know exactly what plants mammoths, mastodons, and ground sloths ate from fossils of their dung. The plants they ate are still abundant today. For example scientists found deep layers of mastodon dung at the Page/Ladson site on the Aucilla River. Mastodons ate over 50 plants, all of which exist today. Most abundant were cypress twigs and buttonbush twigs--both plants are common throughout the southeast. Google the Aucilla River Project. It's a really nice virtual museum.

Moreover, the extinction event affected both browsers and grazers. If climate change caused the extinctions, one would logically expect either browsers or grazers to become extinct, not both. For example mastodons were browsers. If climate change caused changes to the vegetation that dried the forests out converting them to grasslands, it should have benefited the grazers--mammoths and bison. Or if the climate became wetter, the forests would have closed benefiting browsers like mastodons and tapir but eliminating grazers. But that didn't happen.

Bowkill,

I know which quote you're referring to. David Meltzer of SMU said that. I've studied his work and have come to the conclusion that he's an illogical idiot. Hunting mastodons and mammoths was well worth the risk. All Indians had to do was use an atlatl to project a spear into a vital area like the bladder. Then, they'd back off and track the animal until it died of blood poisoning. African natives using spears still use this method. In fact at the Taima-Taima site in Venezuala it appears an Indian threw the killing spear up the mastodon's rectum, thus causing fecal matter to permeate the bloodstream.

There are at least 8 mastodon kill sites and well over a dozen mammoth kill sites. That's plenty of evidence considering the rarity of fossil preservation.

Ashcraft,

You're factually incorrect about a number of items.

Anthropologists agree that Indian populations were reduced by 85% upon contact with Europeans. Indians had no immunity to smallpox, influenza, whooping cough, etc. That's just a historical fact. White tailed deer did not speciate after the extinction of the megafauna. White tailed deer are found abundantly in Pleistocene fossil sites.

Ground sloths did not survive in Cuba until the 1500's. They died out 6,000 years BP, exactly the time man colonized the island.

Horses did not survive past the megafauna in Alaska.

Decidious forests in the eastern half of North America never became desert.

There are no probosicideans in non-tropical areas.

I don't know where you get your information from but it's totally wrong.

Boesse,

The extinction events in Europe do coincide with the appearance of man. They cluster before the last glacial maximum and after. Animals survived in Europe during the coldest period when man was not present there. Man's overhunting of the megafauna in Europe was interrupted by bad weather.

[Guest solius symbiosus]

Not just acient people Boesse. It still holds true today.

Wow! That is a tad bit ethnocentric. Especially, considering we have European friends on this board.

[ashcraft]

Ashcraft,

You're factually incorrect about a number of items.

Anthropologists agree that Indian populations were reduced by 85% upon contact with Europeans. Indians had no immunity to smallpox, influenza, whooping cough, etc. That's just a historical fact. White tailed deer did not speciate after the extinction of the megafauna. White tailed deer are found abundantly in Pleistocene fossil sites.

Some anthropologists do agree with that, far from most however. Historical fact is inherent to the source. Whitetails are, or where, in the middle of a speciation event, there are between 16-30 subspecies (before we started restocking) of all shapes and sizes. Do you think a Key's deer could breed with a Northern whitetail?

Ground sloths did not survive in Cuba until the 1500's.

They died out 6,000 years BP, exactly the time man colonized the island.

There are a number of publications, and wikipedia (for what that's worth) that quote the 1500's extinctiion date, they all reference back to "Extinct and Vanishing Mammals of the Western Hemisphere".

Horses did not survive past the megafauna in Alaska.

You were correct on that one, I rememberd incorrectly, the article was in Nature, and stated the Alaskan species of horse went extinct before humans arrived..

Decidious forests in the eastern half of North America never became desert.

That may or may not be true, I was speaking of Missouri, which is west of the Mississippi. A good read "A Holocene Vegetaation Record from the Mississippi River Valley"

There are no probosicideans in non-tropical areas.

Elephants are found in the African deserts, and Savannahs, hardly tropical in the sense you were using it.

I don't know where you get your information from but it's totally wrong.

My information isn't as wrong as you think. Once again, regarding plants, (I'll write slowly) because they are still found today doesn't mean that all the adults didn't die for a year or two, that is the inherrent advantage of having seeds. If a growing season is lost for a year, due to some cataclysmic event, large herbivores die, then the next year the plants grow again.

Brent Ashcraft

[CaitlinAnn]

Interesting read, guys. I wish I had something productive to add but I don't.

[RJB]

Im going to let you guys hash this one out. Im just going to try to find more time to hunt for fossils and prep them. I wish you all the best of luck. But I wonder what a good smoked mammoth roast tasted like?

RB

[Guest solius symbiosus]

Im going to let you guys hash this one out. Im just going to try to find more time to hunt for fossils and prep them. I wish you all the best of luck. But I wonder what a good smoked mammoth roast tasted like?

RB

In the first part of the last century, I think it was the British Paleontological Society that dined on Mastodon Steaks that had been recovered from a Siberian beast.

I can't recall the details, but I think it was 1925 in London.

[Uncle Siphuncle]

Since mammoth steaks are hard to come by these days, why don't we try Florida manatee instead? Bowkill tells me they are delicious!

[Guest N.AL.hunter]

MarkGelbart, You're wrong.

"Na Hunter,

You're wrong. Extinction caused by climate change inherently means species of plants the megafauna ate must have become extinct."

A food source plant did not have to go extinct in order for the animal that eats it to go extinct. Here is an example: Let's say we have an animal that has evolved to eat only one type of plant, for example a Panda Bear that eats only Bamboo. (just an example to use for this discussion) Let's say that the Pandas are geographically isolated on the western side of a high mountain range, but the bamboo they eat can be found on either side of the range. A climate change causes severe drought by limiting the evaporation rate from the nearest ocean. This kills off the bamboo on the rain shadow side of the range where the Pandas happen to live. They die. They become extinct. The bamboo lives on on the rainy side of the mountain. It is not extinct.

Simple thought experiment. I am not saying this is what happened with the megafauna, just that climate change can cause plants to become less numerous that they were or become geographically isolated which places stress on populations that require those plants to live. Add to that stress hunting and disease and you can get extinction.

[LanceH]

Dang, the freezer burn must have been AWFUL!

In the first part of the last century, I think it was the British Paleontological Society that dined on Mastodon Steaks that had been recovered from a Siberian beast.

I can't recall the details, but I think it was 1925 in London.

[Ramo]

Since mammoth steaks are hard to come by these days, why don't we try Florida manatee instead? Bowkill tells me they are delicious!

Manatee are kind of rare out this way, I prefer Whooping Crane.

[MarkGelbart]

Na Hunter,

There's no evidence that all the plants died out in one year. If that happened, many of the plants would have become extinct. Not all of them, but some of them would have. Besides, if all the plants died in one year, all the animals would have become extinct as well but that didn't happen. Not even scientists who believe climate change caused the extinction of the megafauna believe in the scenario you suggest.

If you want to understand climate change as a cause of extinction of the megafauna, I suggest you study R. Dale Guthrie's work. He has the most plausible reasoning. I don't agree with it, but at least he makes sense. The scenario you put forth is not realistic.

BTW, pandas are not extinct.

Ashcraft,

You obviously don't understand what speciation is. Speciation is the evolution of one species to another. A subspecies is not considered a different species. And yes, a Key West white tail could interbreed with any other subspecies of white tail.

According to the book "The Americas before and after 1492: Current Geographical Research" from the Annals of the Association of American Geographers it is the consensus of geographers that 85% of American Indians were wiped out by disease. The Spanish even kept censuses and historical records of the deaths. It's in the historical record and is not even up for debate. Indians were wiped out by disease--this is fact, not opinion.

Wikipedia is not a reliable source. Anybody can write anything on wikipedia. There is no fossil evidence of giant ground sloths in the Carribean that are more recent than 6,000 BP. Do a google search on Carribean ground sloths. You'll find a paper written by Martin, Macphee and others. The timing of ground sloth extinction is evidence in favor of overhunting by man.

Missouri never completely became a desert or even close to a desert in the past 50,000 years. There's an excellent record of plant and animal fossils at the Bony Spring site in the state. Mastodons were common througout and alligators even lived there 50 ka. At 50 Ka it was a closed hardwood forest. During the LGM it became an open spruce parkland. Then it switched back to hard wood forest. There's been no desert there in the fossil record.

You are wrong about many if not all of your facts as I so demonstrated.

[safossils]

MarkGelbart

I’m certainly no expert on this subject, but I generally agree that the scientific evidence uncovered in recent years points to hunting by humans as the main factor in the Extinction of Pleistocene Megafauna in North America. However, the model that you’ve put forth seems to completely exclude any other factors in the extinction. I think there is some evidence as pointed out by others here that there are other factors that could have, or may have been involved. Unfortunately, you are defending your model as if it were fact, and not just another theory based on the current available evidence. Who knows, evidence may be uncovered in the future that completely reverses this thinking.

Walt

[ashcraft]

Ashcraft,

You obviously don't understand what speciation is. Speciation is the evolution of one species to another. A subspecies is not considered a different species. And yes, a Key West white tail could interbreed with any other subspecies of white tail.

It sounds like you are speaking of anagensis, largely dismissed. A key's deer couldn't interbreed with a northern white-tail, they are geographically isolated from each other. Size isn't the issue yet. Could a St. Bernard and Chihuahua interbreed and produce offspring? They are the same species aren't they?

According to the book "The Americas before and after 1492: Current Geographical Research" from the Annals of the Association of American Geographers it is the consensus of geographers that 85% of American Indians were wiped out by disease. The Spanish even kept censuses and historical records of the deaths. It's in the historical record and is not even up for debate. Indians were wiped out by disease--this is fact, not opinion.

Now you are going from anthropologists to geographers as your source. I reread last night a portion of the "Prehistory of Missouri" a source and textbok used in several universities. Disease was listed as only a portion of the deaths of Native Americans. Back in the day, all the Mound Bulders in this part of the world were wiped out by Spanish disease. It now appears they were gone by the mid 1300's.

Wikipedia is not a reliable source. Anybody can write anything on wikipedia. There is no fossil evidence of giant ground sloths in the Carribean that are more recent than 6,000 BP. Do a google search on Carribean ground sloths. You'll find a paper written by Martin, Macphee and others. The timing of ground sloth extinction is evidence in favor of overhunting by man.

I gave the source for Wikipedia, I can't do better then that.

Missouri never completely became a desert or even close to a desert in the past 50,000 years. There's an excellent record of plant and animal fossils at the Bony Spring site in the state. Mastodons were common througout and alligators even lived there 50 ka. At 50 Ka it was a closed hardwood forest. During the LGM it became an open spruce parkland. Then it switched back to hard wood forest. There's been no desert there in the fossil record.

You are completly wrong, there are desert conditions in Missouri today, I drive by them every weekend. They hold a very unique and diverse assemblage of fauna and flora, including cacti, yucca, hognose snakes, etc. Read the paper I recommended, there are also others available on the same subject. There is a considerable record of significant drying throughout the central US from about 12,000 years ago to 9000 years ago.

You are wrong about many if not all of your facts as I so demonstrated.

The desert elephants and I are glad of your corrections.

Brent Ashcraft

[worthy 55]

Dang, the freezer burn must have been AWFUL!

LOL LOL!!!! One heck of a food saver you would need LOL LOL!!!!!!