A converation about overpowered trained combattigers led to a converastion about humans and pointy sticks, and the extinction of a lot of the worlds megafauna.
We had 17 periods of global warming and climate change without a mass extinction.The extinction disproportionately affected larger animals... which should, if anything, be better able to adapt to changes in climate. At some point, wolf populations dropped to the point that they may have been extripated from north america and had to recolonize from Asia. Considering that wolves can live from mexico to alaska with only moderate changes in body shape it seems unlikely that they weren't able to adapt to climate.
When did the North American megafauna become extinct, exactly? (Answer, over a period of some 10-20 thousand years). When did humans arrive in North America- exactly? (answer, we still don't know but recent discoveries have pushed back the date by more than 10 thousand years).So? It took a while for populations to build up high enough to cause extinctions.
And, look at it another way. During that period there were far less than 1 Million natives in North America (estimates say around 100000). Right before Columbus, there were 100 million natives- and living happily with 100 million buffalo. The buffalo were a thriving population.Bison are hard to hunt without horses. They're more apt to consider a man sized opponent a threat, don't have the gigantic payoff that a mammal does, and have a reproductive rate twice as fast, reach sexual maturity in 2-3 years (estimates based on elephants would put mammoths at 8-9 years). They're MUCH better set up to withstand hunting pressures from humans with pointy sticks.
Or another way. since the invention of modern firearms, mankind has not managed a single extinction of a land mammal megafauna species, despite having weapons hundreds of times more deadly and having a population SEVENTY THOUSAND TIMES GREATER.And much more efficient sources of food as an alternative (agriculture+/including animal husbandry) that weren't available.
Species are hard to extinct by simple hunting. Even some of the best examples- Passenger pigeon for example- was more depletion of the hardwood forests than hunting, altho no doubt hunting played a part.We were low on hardwood forests but we were never out of them. They also did fine on agricultural seeds.
No serious modern scientist accepts the Pleistocene Overkill hypothesis any longer.Bulte, Erwin, Richard D. Horan, and Jason F. Shogren. "Megafauna extinction: A paleoeconomic theory of human overkill in the Pleistocene." Journal of Economic Behavior and Organization 59 (2006): 297-323.
Fiedel, Stuart, and Gary Haynes. "A premature burial: comments on Grayson and Meltzer's "Requiem for overkill"" A premature burial: comments on Grayson and Meltzer's "Requiem for overkill" 31 (2004): 121-31. Elsevier. Web. 9 Nov. 2009
The authors are engaged in a discourse over the competing ideas of Pleistocene extinction with authors of a previous article While its great material pertinent to my topic, I can’t help but notice that it reads much like an internet conversation, except the insults are much more subtle and verbose. They accuse other authors in the journal of ad homs, appeals to authority, lies by omission, sophistry, and not doing their homework.
Currently it seems to be Climate change was the trigger with hunting (and other human interventions) putting the coffin nail and new species finishing them off. In other words, scientists don't accept simplistic hypothesis without any shred of proof other than a coincidence that turns out to be false once you take a good look at it.Again, there were 17 previous environmental shifts without a huge extinction event. The only new factors were 1) humans and 2) fewer available species
I have a hard time believing that when I was doing the research for the mammoth report a few years ago I ran into the only overkillers out there.
Dotting
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{rolls on "Table of Calvin's Dad's Explanations"} Cro-Magnon PETA people kept splashing red paint on the mammoths and screaming 'Fur is Murder!' so often that all the mammoths died of embarrassment.
Even within the supposedly hallowed halls of science, these debates typically divide along the ideological lines of the scientists involved.
At least in the case of the mammoths, most likely it was a combination of rising temperatures and the introduction of hunting pressure from humans.
As far as I know, while early North American mammoth hunters may not have had bows, they likely had atlatls, which are extremely effective projectile launchers.
We talked about this in my Environmental Economics course last spring. Megafauna are simply too easy targets. They provide more food than a tribe can eat before it rots, they're bigger and easier targets, they tend to be slower, etc.
To me there's no question that humans were the primary cause of these extinctions. Heck, we're still seeing this today. Why to indigenous peoples hunt whale or bear or bison? We know that native americans hunted buffalo by running hundreds off a cliff.
Then there's the case of the passenger pigeon which, I know, doesn't seem like megafauna, but in the case of human predation it behaves precisely like one. It moved in swarms, sometimes hundreds of miles wide, so if you shot at it you were guaranteed to hit something. It's hard to pass up a sure thing.
That said, there's also no reason to discount other modern phenomena, such as how global warming has increased mosquito and tick populations in Canada which is leading to the extinction of the moose. In fact I'd argue there was likely a similar phenomena 10-20,000 years ago when the glaciers were receding across North America.
Overall I think it's simplistic to blame any such event on a single factor, but I think that, considering the paleontological and paleoecological evidence for it, saying humans had no hand or even downplaying mankind's effect on the extinction event is sophistry.
...A converation about overpowered trained combattigers led to a converastion about humans and pointy sticks, and the extinction of a lot of the worlds megafauna.
We had 17 periods of global warming and climate change without a mass extinction.The extinction disproportionately affected larger animals... which should, if anything, be better able to adapt to changes in climate.
Wait... what?
Large animals are the first to go in any climate change event. They take gigantic amounts of food to power them. Changing climate usually means less food, or the loss of a particular sort of food, which means starvation.
Smaller is better. Evolution has favored it over and over again. This is why we have small versions of once giant animals in the world and few of the actual giant animals themselves.
I can't imagine a more simple example of how evolution works, than the question of feeding a large wolf compared to a small wolf, or a giant sloth compared to a small sloth.
Well, that over a relatively short span of time, predation can be just as powerful a selective pressure as resources.
Regardless your point stands that smaller creatures are better able to adapt to new paradigms, as a general rule.
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{rolls on "Table of Calvin's Dad's Explanations"} Cro-Magnon PETA people kept splashing red paint on the mammoths and screaming 'Fur is Murder!' so often that all the mammoths died of embarrassment.
And we'll do it again in a heartbeat, filthy slaughterers!
Even within the supposedly hallowed halls of science, these debates typically divide along the ideological lines of the scientists involved.
At least in the case of the mammoths, most likely it was a combination of rising temperatures and the introduction of hunting pressure from humans.
As far as I know, while early North American mammoth hunters may not have had bows, they likely had atlatls, which are extremely effective projectile launchers.
In 10th grade we studied the mbuti.
One guy became chief by figuring out how to whack elephants: the strategy is to run up underneath the elephant with guile, stab it in the heart a bunch of times with a spear, and haul ass before it kills you or falls on you. With any luck it will bleed to death shortly thereafter.
That's probably how you do it with flint. Either that or scare them with fire to run over the edge of cliffs and such.
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If you are going to hunt Bison on Foot you hunt them with fire. Its the one thing even an aggressive animal will have the sense to fear. likewise a Hairy mammoth should be easily distracted by the burning sensation of its hair and flesh cooking.
I don't know where I recall it but a documentary spoke of Mammoth remains in a lake in the Rocky Mountains where they found Mammoth bones cleaned off as though the meat had been boiled off the bones. Something that might happen to Mammoths seeking refuge in Warm heated Water that slowly cooks the animal to death.
There are still some oddities -- if the teratorns (huge birds that looked like giant vultures) were really small-prey eaters, not carrion feeders, it's not clear why they would have died out. (EDIT: Not clear to me, that is. I'm hardly an expert on Pleistocene megafauna, just an interested nature/wildlife fan.) They certainly don't look like prime human food species.
I am personally not 100% convinced that carrion wasn't an important dietary component for teratorns. It's pretty compelling that the largest north American scavenging bird to not go extinct (California Condor), is also from isotopic evidence the only large scavenger to make use of marine resources such as stranded whales. The other extant NW vultures either are small carrion specialists (Turkey Vulture) or small/random prey generalists (Black vultures tend to go after garbage, dead fish, etc). We know vulture guilds are far far more complex in how they divide up the carrion supply in Africa and Asia, hence why there is a greater diversity of vultures there than in NA currently, although we know there were several extinct species
Similarly, one would think that some of the "smaller" predators the Americas lost, like the giant cheetah-like cat Miracinonyx, could have lived off deer and pronghorns and such. (Supposedly pronghorns may have developed their speed to get away from stuff like that, as they are now ridiculously faster than their only possible predators nowadays.)
Cheetahs are today at the bottom of the carnivore hierarchy, and frequently lose there prey to other carnivores. They seem to be quite vulnerable to predator competition. My labmate has done dental wear analysis on Miracinonyx and has found that it was also specialized in it's diet. It's probably also worth mentioning that that we lost several species of pronghorn during the end-quaternary extinctions, and it's probable that the living population suffered extreme population declines followed by recovery. It wouldn't take much loss of prey diversity to take out Miracinonyx.
since the invention of modern firearms, mankind has not managed a single extinction of a land mammal megafauna species
Depends on how you define species -- if the tarpan is considered a different species from the domesticated horse, it's thought to have become extinct 1909.
(The aurochs has a similar question of definitions, and it went extinct in the 1600s).
And while the thylacine doesn't technically meet the usual minimum size for megafauna of 100lb or 50kg, it WAS the largest mammal predator of its environment. (Extinct 1936)
hhhmm...I have no idea where the previous poster was getting his information from regarding no megafaunal extinctions since the advent of guns
Arabian Ostrich, Atlas Brown Bear, Bubal Hartebeest, several species of middle-eastern gazelle, several subspecies of tiger, Bluebuck, Caucasus Wisent, Quagga, Schomburk's Deer, etc are all extinct post introduction of guns. Several other Large Herbivores, including the Bison, Bontebok, Black Wildebeest, Wisent, etc were only saved at the last minute. Quite a few ungulates, especially in SE asia and the Middle-east are severly endangered from poaching and sport hunting with guns, and some species may technically be extinct. It also ignores the huge range reductions many species suffered from hunting.
Even so, outside of south Asia and Africa, most of the megafauna was already depleted. When all of your most vulnerable taxa are already gone, of course the survivors will be less impacted.
Even within the supposedly hallowed halls of science, these debates typically divide along the ideological lines of the scientists involved.
At least in the case of the mammoths, most likely it was a combination of rising temperatures and the introduction of hunting pressure from humans.
As far as I know, while early North American mammoth hunters may not have had bows, they likely had atlatls, which are extremely effective projectile launchers.
At least amongst the Paleo community, I don't think there a whole lot of doubt that a lot of the end quaternary extinction events were anthropogenic. Most of the arguing seems to be based on divisions amongst the research schools (Paleo versus Anthro/Archae) Sure, there were probably some background extinctions, either because of climate change (Florida Bog Lemming) or competition with newly immigrating taxa (Stag Moose). But for most mammals, humans seem to be the source of blame.
Climate change could have weakened and made populations more vulnerable to extinction via drought, which would have had a deleterious effect on populations and might have restricted populations around waterholes, etc, making them easy game.
However by itself it wouldn't have cause much of a problem. For starters, Holocene and Pleistocene climate change is well studied, and the Holocene was not especially unusual when compared to past event that the same species survived with no problems. In fact, the warming was actually less than that of previous intervals. You should also take in account there wasn't just one species of Wooly Mammoth. The Columbian Mammoth for instance was adapted for warmer climates and occurred throughout the southern and central states into Central America. We also had Gomphotheres in the new world, which basically ranged from Arizona/Northern Mexico, as far south as chile and up into the Andean mountains. The tropics were still...tropical...and climate change can't really explain why this taxon would go extinct.
Wait... what?
Large animals are the first to go in any climate change event. They take gigantic amounts of food to power them. Changing climate usually means less food, or the loss of a particular sort of food, which means starvation.
Smaller is better. Evolution has favored it over and over again. This is why we have small versions of once giant animals in the world and few of the actual giant animals themselves.
I can't imagine a more simple example of how evolution works, than the question of feeding a large wolf compared to a small wolf, or a giant sloth compared to a small sloth.
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Except the climate change at the end of the Pleistocene and beginning of the Holocene wasn't any more dramatic than repeated climatic events, and was actually less dramatic.
Being large actually does provide a lot of benefits. If the climate warms/cools, you have the ability to easily shift your range. Large animals can more effectively migrate large distances, and there is at least some tentative data to suggest that some of the NA megafauna was migratory.
Large mammals get lots of other benefits too.
They can exploit a greater variety of food sources. A large carnivore can pretty much eat whatever it wants.
They are harder to predate. A mammoth in a herd would have been immune to most predators, with maybe the exception of the occasional skilled lion pack
Their surface to body ratio is smaller, and so they actually need proportionally less food. A mammoth can shrug off several days without food without a problem. A mouse in contrast will die in that time.
They can actually eat tougher, less nutritious food. Large size means the ability to have large guts for fermentation, which means abundant food sources (such as grass) can be efficiently processed
Really the two weakness for large mammals are a low birth rate (big mammals have large offspring, which means smaller litters, longer pregnancies, and longer nursing period) and problems with severe increases in global temperature.
The latter has only occurred once during the Cenozoic, during the PETM event. This led to tropical rainforests in the high arctic, and overall dwarfing of mammalian taxa. Past the PETM we see absolutely no trend in decreasing size of lineages over time. this has been tested numerous times for different mammal lineages; my own dissertation actually focuses a lot of body size change through time in pinnipeds, for instance.
Bruunwald has the right of it.
I don't know what led DrDeth to his opinion.
Another point is that bigger animals are favored in colder climates because bigger animals lose body heat slower whereas smaller animals are favored in hotter climates for the opposite reason.
Bergmans rule
Colder climates generally lead to "larger animals". However it should be noted that this is more a intra species phenomena, not a interspecific. Large animals can actually do quite well in tropical climates as well. See extant elephants, rhinos, giraffes, etc.