Overkill, Overchill, Overill? Megafaunal extinction causes

(Comments moved from the Neanderthal thread)

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Also because of the thickness of the skin and the high muscle to fat ratio the meat of an elephant is not as good as other large herbavores

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But what can't be eaten can be used for other quite useful purposes, from shelter to clothing.

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This still does not address the extreme lack of kill sites

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I find it surprising that you would expect to find even a significant percentage of total kill sites from a species hunted in such a vast range for such a (geologically) insignificant time. We don't hold anywhere close to such a standard for other fossils - why would we expect it for mammoths? A much more reasonable stance would be to compare the number of mamoth fossils found at kill sites during this time period to those not found at kill sites.

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Aside from the fungi that live on Choloepus

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And insects. Which live in the hair, not the skin (or more importantly, the muscle).

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I can hardly imagine anyone subsisting on sloth meat

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Why? Because of the size? If so, then Mylodon isn't addressed.

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In any case, Mylodon, Northrotheriops to a lesser extent, was full of ossicles throughout the skin and probably not so easy to kill.

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Humans are inventive. Depending on species, you may find mammoths that were upwards of 10 tons. Mylodon was only the size of an ox. Yes, it's better armored - but so? Humans have fought off far more fearsome armored creatures than that - for example, Megalania prisca. Throughout history, humans have killed crocodiles and alligators; small families of islanders alone have fought off komodo dragons, which have some pretty impressive armor; etc. I have little doubt that humans could have killed mylodon. Our chiefest hunting ability has been to learn the weak points of our prey.

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This assumes that the immigrants practiced a more non-economical form of subsistance i.e. killing more than you need in the lands they came from. I don't know that there is any evidence for this.

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There's tons of evidence that early natives to different areas employed incredibly ecologically destructive practices. When westerners first found Easter Island, there wasn't a tree on the island more than 10 feet tall, and a devastated people in constant warfare; this is why the presence of giant statues (which would have needed scaffoldings to make) was so surprising. Digs on the island have revealed that it used to be almost completely forested.Likewise with the Anasazi. For a while, it was a puzzle how the Anasazi developed such a large civilization in the middle of a desert. However, archaeology has revealed that initially, Chaco Canyon wasn't a barren desert - arid, yes, but it was forested with pine and fir trees. As logging increased, they responded not by reducing consumption, but increasing the range that they brought in resources from. They built elaborate log-roads to get their wood in - from as far as 80 kilometers. Being a fairly delicate area, the region was inexorably altered.I find it amazing that many people have trouble accepting that, given the track record of humans, that this would happen to the megafauna. What we're dealing with is a "land of plenty" situation. Humans move into an area where animals are not adapted to survive with humans hunting them or competing for their food supply, and where the flora is in rough equilibrium with its environment. Humans encounter what seems like a limitless hunting and harvesting paradise. A human population explosion occurs, and a native species population bust occurs, with some species going extinct. It has happened across the entire planet. If too many species go extinct in a region, the human populations there will decline or die out as well. As a consequence, over time the more balanced resource-utilizing societies are selected for.And I agree with Speel-yi - there is far too wide of a range of species that go extinct to be explained by disease alone. I don't buy into the concept of a lethal disease that happens to jump species, but never made it over before we did, despite all of the migrations by other species of animals. Disease may be part, but wasn't the cause itself.------------------
"Illuminant light,
illuminate me."

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Where are the remains of this shelter and clothing considering how many other things are preserved in the same environments?

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1) How much ancient clothing and shelter *has* been found? Hides don't preserve well over the aeons. Where do you think they lived, in ice caves? Native americans, when westerners encountered them, were living in shelters made of the hides of the large game that they hunted. Why would you expect otherwise from the Clovis people?2) It has been found clovis people used numerous bone tools (although their hunting tips were flint).The question is not how many kill sites. The question is the ratio of the number of mammoth fossils found at kill sites, to the ratio of fossils found elsewhere from during this brief time period. Kill sites are going to be small and isolated, making them harder to find. Also, kill sites will only reflect places where killing mammoths was related to geography.

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I was being a bit ironic here since eating a sloth sounds disgusting. Mylodon had ossicles throughout its skin and had, like mammoths a low fat to muscle ratio...not really idea for subsistence.

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And still would feed a person for an incredibly long time.

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We are not talking hunting. We are talking hunting to extinction..every last member of the species gone.

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In the case of the mammoth, I am not. This is now the third time I have had to say this. I believe that hunting was *one* factor, of many. Am I going to be made to state this yet again?

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Why is it that the humans prior to the end Pleistocene were so much more inventive that they decimated the megafauna and then almost NO subsequent megafaunal extinctions occurred in the ensuing 10,000 years?

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How many times to I have to state this as well? Please, Mammothus - for the last time: The cultures that destroyed all of the large game in their areas would themselves be selected against. It takes time for a steady state to be reached. If you have an argument against *this*, please state it, but don't make me repeat it yet again.

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I am more surprised that people immediately assume that all cultures will be completely wasteful and destructive...even without evidence.

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Care to address the Anasazi or the Easter Islanders? I can give you plenty more examples of native environment destruction if you'd like. Want some native animal extinctions which are obviously due to hunting? I can discuss Madagascar and New Zealand if you'd like.

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The population boom does not have evidence.

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Stephen Mithen, of the McDonald Institute for Archaeological Research in Cambridge has put the human population at 12 million before the mammoths fell significantly, and had an extinction at about 5,500 years after human arrival. Here's some info about his computer modelling:http://www.dreamwell.com/ali/anthro/mammoth.htmThey also discuss some critiques of the overkill theory - if you would like to bring them up, by all means do. Note that this is a simulation for the kill-only cause of extinction, which I do not agree with.

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There is also little evidence that the end Pleistocene environment was in equilibrium. Dramatic climatic changes were occuring.

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No - equilibrium with *humans*. Since humans and their effects were the chief cause of the extinction (directly and indirectly), and the climate is just one of many factors, it itself isn't that major - if equilibrium can be reached with humans.

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There would have been no humans even there if the climate changes had not occurred. Hunter gatherer societies rely much more on the females gathering than the supplemental protein the hunters bring in.

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Completely true - in societies that are in equilibrium, in temperate climates (the number that I've typically heard is 80% from gathering, 20% from hunting in such environments). If the society is focusing heavily on hunting for calories, it is not in equilibrium. If we're not talking about a temperate climate, then gathering isn't as major of a percentage of calories. How many calories did the innuits traditionally get from plants, for example?

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Why are African megafauna, which are hunted and have been for even longer by humans, not extinct? Elephants numbered in the millions in Africa, why were they not "the land of plenty" leading to full scale Rambo attacks to decimate them and lead to a human population explosion?

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For the last time: Because they are in equilibrium. Cultures that have hunted the species in their area to extinction have been selected against. The end result is society whose values and way of life reflects as much as they can take from the local environment without damaging it. Likewise, the animals themselves are more adapted to human predation, learning to instinctively fear this (relatively) light, unassuming creature.When europeans moved to the new world, they suddenly found passenger pigeons, in abundance. Europeans had not traditionally relied on them as a food source - they had a fairly sustainable system of agriculture, livestock, and limited game hunting. Suddenly, here is this plentiful food source. We hunted them to extinction. And largely not through technology - it was mostly done through trapping and bagging. Why should we believe that the continent's natives were somehow different when *they* arrived?

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There are a lot of viruses and bacteria that can jump among species and cause mass die offs.

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Name one that can jump between most large mammal species that is highly lethal. Just one. Yes, there are diseases that can jump species. There are diseases which are lethal. But one that can jump to such a broad range of species, and is lethal to all of them, is not evidenced by what we find in the world.

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And all you have to do is nail a few keystone species like mammoths and that will cause problems for everyone else. And megafauna would be very suceptible since their gestation times are so long. Kill all the baby elephants quickly, it will take two years before the next round are born. If the adults are sick it will take longer if at all.

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Exactly - that is why the cumulative effect of many types of change is so critical.

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And I never said it was a singular cause...

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You've certainly implied it.P.S. - clovis rambos - Google Search------------------
"Illuminant light,
illuminate me."

Ok. Then name a series of lethal diseases which can cover the wide variety of species that we see go extinct.It's just not feasable. We've seen plenty of hunting to extinction, and plenty of habitat-destruction-to-extinction, etc, but never before witnessed a disease-to-extinction, especially not across such a wide variety of species.------------------
"Illuminant light,
illuminate me."

Thank you, Quetzal, I was not familiar with the morbillivirus. However, it is worth nothing that the virus has never established itself in North America or New Zealand. That doesn't mean that some other disease could have been the culrpit, but I would expect that we would see at least some New World reminant of whatever disease it was.The die-offs we have seen occur everywhere humans have arrived, right after humans have arrived. We're not just talking about ungulates here, we're talking everything from Megalania prisca (a giant monitor lizard in Australia) to the Moa in New Zealand and the Elephant Bird (the "Roc" of legend, extinct in the late 1600s), to the large New World mammalian dieouts (Artiodactyla, Perissodactyla, Carnivora, Rotentia, Xenarthra, you name it). Virtually every single time humans have arrived in a place with large animals, this has happened. The concept of a fatal mite or protozoan even affecting such a diverse population, and having followed every migration, in every time period, that humans have taken, really seems quite unreasonable.

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We've seen widely dispersed populations of single species eliminated globally by disease (ex, the global extinction of the snail Partula turgida by the protozoan parasite Stenhausia)

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Funny. I'd say that the biggest cause of the death of Partula turgida was the introduction of a florida snail, to control the population of an escaped African snail. Only the last 5 snails died of the Stenhausia, and that was in captivity - the species was all but extinct anyway. That's nothing at all like this situation Mammothus advocates.

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and we're currently seeing the global reduction of amphibians by the Batrachochytrium fungus

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But nothing close to extinction. Even threatened populations seem to be holding out ok against it.I'm not saying that it's impossible for a species to go extinct from a disease - but I think the species has to be in *severe* trouble already before this can happen. This does not describe the megafauna at all - they were very widespread, across all kinds of climates. Disease may have been a "finishing blow", or something that perhaps weakened their populations, but disease - or even disease and climate together - causing this? Doesn't seem likely.------------------
"Illuminant light,
illuminate me."[This message has been edited by Rei, 10-19-2003]

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Skins, bone huts, every different part of mammoths and various other extinct megafaunal species are found throughout Siberia in excellent preservation. Fairly intact skeletons of megafauna are found throughout North America. Why are all of the shelters etc then absent? You would expect a lot more than what is found if mammoths were being hunted so intensely.

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Some poor-condition mammoth skin has been found in permafrost, but for the most part, it is bones that remain. Especially large bones and tusks. I still find it incredibly odd that you're expecting to find intact shelters from the Clovis civilization. It's not like they built giant cities out of stone and brick (which themselves are hard enough to find). We're talking about bands of nomads living in tents. And, as I stated, bone tools *have* been found from Clovis peoples (want references?). but most are in poor states of preservation.

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2) It has been found clovis people used numerous bone tools (although their hunting tips were flint).

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The question is not how many kill sites. The question is the ratio of the number of mammoth fossils found at kill sites, to the ratio of fossils found elsewhere from during this brief time period. Kill sites are going to be small and isolated, making them harder to find. Also, kill sites will only reflect places where killing mammoths was related to geography.

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If kill site are small and isolated how did overkill bring down a species that was spread from Europe to Mexico in about 1000 years by making pin pricks at the population by hunting?

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A single tribe makes pin pricks. Several million people cause a slaughter.

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Selected against how? They had muskoxen, bison, deer, caribou, moose (Sorry Moose ), bear, marine mammals all megafaunal and all in abundance that they could have turned and slaughtered. Why stop after the truly large megafauna was gone? I see no evidence of negative selection before, during or after the end Pleistocene.

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And there you are assuming again - assuming that regions did *not* experience a killoff of whatever large game were available. Just because a species didn't go extinct doesn't mean that it wasn't heavily hunted, and killed off in specific regions. You know very well that populations of large animals, due to smaller numbers, are less stable and more prone to extinction.

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You can discuss anything you want. Island extinctions do not work exactly the same way as continental with species as widely distrubted as mammoths.

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Madagascar and New Zealand are no small islands. Madagascar is about the size of Arizona. New Zealand is about the size of Colorado. The Moas of New Zealand had a maximal weight of about 300kg, compared to up to 7000kg for a mammoth. They both were herbavores; most of New Zealand's plants seem to have adapted specifically to avoid being eaten by Moas. I can'd find population estimates for moas or mammoths, but given the size ratios, I would expect that the ratio of mammoths in North America to moas in New Zealand would at least be reasonably low, making the population of Moas almost as stable as that of Mammoths.

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And don't try to hang the idea on my that I dont believe humans cannot cause extinction. I just don't see that there is any support for humans being a singular cause or even an important cause of end Pleistocene megafaunal extinctions via overhunting. Even the evidence for moa extinctions as due to hunting pressure has come under fire recently.

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Such as...?

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Island extinctions arent such an open and shut case. Even environmental destruction you are talking about does not explain the mass extinctions at the end Pleistocene

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The environmental example shows how drastically environmentally destructive early native tribes can be. Easter islanders *completely deforested* their island - do you realize what that would do to all species there? The Anasazi turned an area 80 kilometers in radius into a desert. These are not ecologically friendly people. As a result, what happened to them? The easter islanders decimated their populations. The Anasazi effectively dissapeared.In short, they were selected against.

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Here are some more recent studies

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What was that? You cited one study for, and one against, and simply declared that the one against was by an "over the top" guy, despite his very pessimistic assumptions. In case you're not aware, this is a hotly debated issue in the scientific community. What sort of studies did you expect to find?

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You don't think climate is important for species adapted to specific vegetation and significantly colder (or at least stable) yearly temperature cycles? Considering how drastically the landscape changed as a result of the transition from Pleistocene to Holocene, I think climatic impact must have been a tremendous selection pressure on the entire ecosystem.

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The dieouts at the end of the last ice age dwarf those of any other recent ice age. Normally, species have time to adapt due to the selective pressures of changing climate and vegetation, because the process is slow enough. Not in this case.

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Why would you assume that even without equilibrium there would be a shift to something as unpredictable as hunting success from gathering where there is a much higher probability of obtaining calories for your group?

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Unpredictable as hunting success in the arctic? What else do you expect people to survive on in the arctic, lichens or grasses? Even in temperate climates, what do you expect - gathering unknown plants from an unknown region, when there is large prey that has never learned to fear or avoid humans, that can feed a tribe for weeks?

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What evidence is there that Africa was in equilibrium? There were population migrations in and out of the continent. The end Pleistocene climate transitions did not just pass Africa by.

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Not climatic equilibrium - equilibrium with humans, the critical selection factor involved here. Equilibrium with humans involves both the humans having been selected not to overhunt their area, and the animals having adapted to avoid humans.

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If there is negative selection for killing when things are scarce but it is positively selected as soon as there is " a land of plenty" then surely the selectively advantageous overkill would have returned to Africa as a behavior considering that elephant populations were dramatically larger than they are currently.

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Then they are currently, or then they are before the introduction of guns and the ivory trade? BTW, up and down cycles are expected, but I would just like to clarify this point.

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Why would animals as intelligent as elephants be so slow to realize when something is dangerous?

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It's a sharp learning curve. Literally. It's not just the intelligence of the prey that matters. Equally critical are things like the difficult-to-change societal structure elements of the animal (unknown for mammoths), the time for knowlege of dangerous situations to fixate into the population as a whole instead of just a small group, and most critically the memes of the human societies involved not to overhunt.

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Why should I believe that all Pleistocen megafauna were somehow less adaptable in their behavior, that the selection pressure for overkill only works in one direction, that human cultures that did not practice overkill show up in the new world and start but those in Africa without any negative selection against intensively hunting megafuana do not?

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Humans developed during most of their evolution in Africa. There was plenty of time for adaptation both by humans, human culture, and the prey.

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That in Asia and North America humans killed off mammoths and dozens of other large mammals but then their was intense selection pressure to stop this behavior even though there was still megafauna present in abundance?

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Time. It takes time for equilibrium to be reached. There was no magical moment when humans just decided, "Hey! We should stop killing all the animals and altering the environment! We should adopt practicies and social expectations that control our population, instead of reproducing extensively as we have at the rate that filled up this continent".Once again, and hopefully for the last time: Large animals have smaller numbers, and consequently less stable populations.

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And finally, where are all the kill sites? If one accepts a number of 12 million people (which is much higher than any number I have ever heard) killed off ALL the megafauna of the size of mammoths in a short period of time why do we not find hundreds of kill sites that date to this age?

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1) If you want to dig a couple dozen feet down through layers of permafrost or other barriers, across 16,245,000 square miles, be my guest. Talk about unreasonable expectations... 2) For the last time, I do NOT claim that humans killed off all of the megafauna! I am an advocate of the theory that there are multiple causes, of which hunting is just one.

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Direct transmission of the H5N1 viruses from birds to humans resulted in 18 documented cases of respiratory illness, including six deaths

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Influenza, a species threatening disease? Rabies? Please.
Read my response to Quetzal on this front.

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The overkill guys like Alroy don't want anyone to do the research and just accept overkill.

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Yes, no evidence, except for the fact that we've witnessed it occuring with hundreds of species in modern times, and can look to the recent geological record for where it clearly has happened to many others in recent history.------------------
"Illuminant light,
illuminate me."[This message has been edited by Rei, 10-19-2003]

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So there is no evidence because the population was sparse and disperesed but there were so many millions of people simultaneously hunting mammoths that they caused their extinction?

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Are you deliberately being like this? You know very well that 12 million people scattered across over 16 million square miles is under one person per square mile - i.e., scattered bands.

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In addition you propose a hypothesis is valid because NO evidence is left behind? So I guess if 10,000 kill sites are found next week overkill will be invalidated?

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My god, Mammuthus, this is annoying. Please, if you're going to keep indirectly asserting that you would *expect* to find even a measurable percentage of the kill sites in 16 million square miles of land, then please explain why, or stop asserting it. Point to where even elephant kill sites from 100 years ago are found in Africa. We know that elephants were heavily hunted in Africa 100 years ago. Where are the sites? Kill sites typically preserve rather poorly, because they are not buried quickly, as a general rule. Gary Haynes (an archeologist who has studied modern elephants, and elephants in the fossil record) discussed how between 1984 and 1986 he saw 9,000 elephants culled, and has been unable to find any of their bones anymore. In reference to Clovis, "In fact, 15 sites with 50 mammoths dead in them to me is an extremely rich, enormously rich, archaeological record, of something going on over a very brief period."

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And sorry, while you are correct that most mammoths are represented by bone there are tons of skin samples and some almost fully preserved carcasses including Dima from which I have personally observed brain, liver, intestine, heart, blood, etc.

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My claim was that bones are a lot more common than skin, and that what skin remains is typically in poor preservation. Do you have a specific counter to this assertion? I'm sure you're quite familiar with the big dissapointment that was Zharkov.

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Then where is the huge genetic bottleneck in all of these species? Bovids, nope, equids nope, canids, nope...cervids, nope..muskoxen, sure though it is hard to determine if they had a bottleneck at all and some work I am doing right now suggests not.

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Nice assertion. Do you have anything to back it up with, or is it pure conjecture? The work that you're doing "suggests not"? Can you give an example?

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It is relatively small compared to the area from Europe to Mexico where every single last one of the largest megafauna became extinct.

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And as I pointed out and you didn't address, Moas are about 1/23rd of the size of the Mammoths, and so would be expected to be much more stable in smaller populations.

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And in fact for moa extinctions habitat destruction is considered just as plausible as hunting

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Whoah, look what we have here! Habitat destruction, hunting, and other mixed causes - of which hunting is one of them. Exactly what I have suggested this entire time.Are you familiar with the quite common cooking sites filled with butchered Moa bones? Holdaway and Jacomb's population study paper which shows that from hunting alone a population of 158,000 moas (in an area the size of Arizona) would be dead within 160 years? Any of this? Here's a quick summary article:Archaeology - Archaeology MagazineNow this is odd... I reference heavy environmental destruction by both an island tribe, and a continental tribe, and you respond with:

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Which shows how different an island is from continental populations.

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Please explain how you got this. Do you not know who the Anasazi were?

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Considering you have been writing as if I am a stupid fuck for even challenging the holy overkill hypothesis I figured I would demonstrate that not everybody is convinced and that an anonymous internet forum poster such as myself represent the only skeptics...

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I do not mean to sound as if I am insulting your intelligence, Mammothus. However, there are things you need to address. You still haven't explained why you would expect to find all of the kill sites when the land area in discussion is over 16 million square miles. You haven't explained how you get that the ratio of megafauna kill site fossils and megafauna fossils that otherwise show evidence of hunting, to other fossils during this same brief time period, suggests that hunting wasn't a major factor. You've yet to address the ample evidence of massive environmental destruction by native peoples, continental and island. Etc. You can see why I would be insistant on getting answers on these things from you. My apologies if it sounds insulting.

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So the other cyclical changes since the Pliocene where humans were not involved but extinction did occur could not have involved climate change? And I don't know that the extinctions at the end of the last ice age dwarfed previous die offs...the curious aspect of the end Pleistocene die offs was that they so specifically involved megafauna.

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Are you actually trying to claim that this is related to climate change? All of the major human 'invasions' occured at different times (Australia, New Zealand, Madagascar (all 3 not during a time of climate change), North America, etc); the Northern latitudes in the Americas had their bust before the Southern latitudes; the Ice Age was already on the decline during the American dieoffs; islands that weren't colonized with humans didn't experience the dieoffs (the Galapagos, Reunion, the Seychelles, Lord Howe, etc) until recent times; etc. Also, are you trying to actually claim that the Pliestocene extinctions weren't incredibly exceptional for extinctions during periods of climatic change in recorded history? A whooping 43% of North America's mammal genera went extinct during this extinction. 91% of the animals that went extinct were greater than 5 kilograms, and 73% were greater than 44 kilograms. In South America, 46 genera died, 80% were greater than 44 kg. Europe only had 13 genera go extinct, and I'm not aware of any in Africa during this time period.The sad thing is that Wooly Mammoths might have made it, if not for the discovery by humans of Wrangel Island about 6,000 years ago. As soon as humans find it, the mammoths dissapear.

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So all of Europe to Mexico, where most of the megafauna that went extinct was concentrated, was artic?

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They arrived in the New World from the arctic - their culture must have had to be completely adapted to survival in such cold climates to survive - including getting most of their diet from hunting. When expanding further south, you seem to just expect them to suddenly change culture and start farming or whatnot (what do you propose they did for food after getting used to a mostly meat diet, in an area filled with abundant large game animals?)

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The gatherers would still supply a more predictable supply of calories than the hunters...and if a single mammoth could supply the group for weeks, why would they kill every single one and all of the other megafauna (except for all the other megafauna that they left alone)..never prey switch either when the density of one species got to low to be worth it?

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Are you familiar with the extinction of the passenger pigeon? Humans didn't kill every last passenger pigeon - not even close. However, once the population was damaged enough, it was unable to recover. People prey-switched on Moas, also, but they still went extinct. The archaeological evidence switches from butchered moas to other game and shellfish.

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What equilibrium with humans? At this time humans were mass migrating all over the place. You had bountiful megafauna in Africa. What possible selection against killing them all would be in Africa that did not exist outside of Africa?

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What "unusual" migrations were occuring during this period, at a rate fast enough to disrupt long-standing human cultural stances?

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So 10,000 years go by and then Europeans hunt elephants with guns and for the first time put the species under pressure....what is the evidence for up down cycles in elephants prior to this?

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How many times do I have to point out that humans, and human culture, coevolved with elephants in Africa? Whether there were up and down cycles is irrelevant (do you have counterevidence?), although yes, one would expect small up and down cycles. Even a most nomadic tribe taking on highly destructive social memes isn't a threat to elephants in general - just in their particular region.

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It certainly does not show up in the genetic record to my knowledge...quite a bit of variation still is present suggesting a huge effective population size was present prior to the recent hunting pressure

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I'm not arguing that elephants were nearly wiped out by natives. I'm arguing that because of coevolution, that they *weren't*, and that there would just be the typical up and down cycles, nothing dramatic. *You* were the one arguing about instability, and I was mentioning that the population change that you referred to was due to a new population coming in, with a new "land of plenty" situation - europeans with guns, and the ivory trade.

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For some of their prey. But humans (if you don't accept multiregionalism) evolved in a single part of Africa and spread...why didnt they overkill as they spread out? Elephas maximus in India should have been wiped out. Land of plenty, no people, left Africa 4 million years before, did not co-evolve with humans...yet no overkill.

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You seem to expect *every* species that humans encounter to get hunted out of existance. That seems pretty preposterous to me. Different animals live in different types of geographic environments, and with different organizational structures. Furthermore, one would expect that the more recent migrants from Africa would still retain more of the social structure that they lived on before, while the further in the arctic they get, the more their culture will become dependant on hunting the abundant wild game.

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Interesting then that moose (the only animals tested thus far) learned in one generation to avoid predators.

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How do you come to the conclusion that they learned in *one generation*?

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But that is what would have to be believed to accept overkill since they left lots of megafauna alone that were still in abundance.

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Provide one piece of evidence that they were "left alone". They weren't hunted to extinction. That hardly means that they were "left alone".

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Hunting a food source to extinction is not particularly compelling.

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Even the hunting-only people (which, again, I am not one*) seldom believe that the species were hunted to extinction - only that they were hunted to the point where they were unable to recover.

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Oh really? And what is the evidence for this? elphants can reach tremendous population densities. So can other large herbivores...smaller populations than rats? Maybe, but small populations? the evidence runs against that.

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Please, Mammothus. You know very well that the ability to sustain an animal is generally relative to its size (at least, I *assume* that you do). The more massive it is, the more calories it needs to consume, and the smaller its population will be (on average).

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Should not have to, most of the late mammoth finds are in areas that are not permafrost so the kill sites should be easy to stumble over.

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Actually, I would expect them to be harder, because they won't preserve as well.

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Except you have made clear you discount anything related to climate or pathogens as factors...in your response to Quetzal

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Better work on improving those reading skills. I'll quote:

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'm not saying that it's impossible for a species to go extinct from a disease - but I think the species has to be in *severe* trouble already before this can happen. This does not describe the megafauna at all - they were very widespread, across all kinds of climates. Disease may have been a "finishing blow", or something that perhaps weakened their populations, but disease - or even disease and climate together - causing this? Doesn't seem likely.

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Sounds like I'm advocating a "multiple causes" hypothesis, doesn't it? I'm stating that disease and climate together isn't enough - what also is needed is changes in population through hunting of the animals, hunting predators, hunting prey, etc; altering of the flora; etc.

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Depends, if you are immunologically naive and the population densities are as low as you have been claiming all you have to do is kill off the young (which are more suceptible anyway) and in a generation the population has collapsed.

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Yes. "Only have to kill of the young". Now, where has this happened to cause a species to go extinct?

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Even mild viruses can have a huge impact on megafauna for example elephant herpes of Loxodonta is often fatal to Elephas. The two genera can no longer be housed together (if you want a successful breeding program or dont want to blow the zoo budget on gancylovir).

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I'll repeat. Now where has this happened to cause a species to go extinct?

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We have had megafaunal extinctions on the scale of the end Pleistocene in the last 10 K years? Please present this data. It would be a Science paper at the very least and a discovery of the century.

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They need not be on the scale of the end of the Pleistocene. What you are asking for is essentially impossible, since humans had, after this, moved into all of the world's major land masses. However, extinctions relative to the sizes of the land masses that were moved into after this point, clearly due to overhunting and other human-related causes, are quite observed.------------------
"Illuminant light,
illuminate me."

Quetzal,First off, you'll notice that the first thing I did in my response to you was to thank you for your hyperdisease example. Secondly, I apologize for pigeonholing you into the role of a defender of the disease-only hypothesis; as you'll notice, the same is happening to me concerning kill-only. I do believe that disease may well have played a role, but that it hardly could be blamed, even with climate, for what we witness at the end of the Pliestocene.

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it was an example of a pathogen that countered your assertion that no such pathogen exists

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Which I thanked you for. It would be nice if you would at least acknowledge humility.

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Your argument, that rinderpest hasnt been established in NA or New Zealand is specious IOW, so what?

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That wasn't my argument at all. Read again. I quote:

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That doesn't mean that some other disease could have been the culrpit, but I would expect that we would see at least some New World reminant of whatever disease it was.

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(emphasis added)

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In the case of the Late Pleistocene event, even in areas which were unsuitable for human habitation, isolated or relictual populations were ALSO decimated.

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I would be curious as to what sort of regions you are thinking of here, in which evidence of megafauna exists.

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Im sorry, but no matter effectively a group of humans managed to extirpate multiple species in the constrained space of an island using primitive, essentially hand tools (and theres little question that the Maori accomplished that feat in a couple of centuries on New Zealand),

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Or faster. And note that New Zealand is the size of Arizona. I don't have range plots for the various megafauna, and I know that many were widespread, but I wouldn't be surprised if there were at least a couple who had a range that size.

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Although its pretty fruitless to speculate on effective population size in a large migratory species like Mamuthus primogenus, overall were talking about (on two continents) at a minimum 10^7 to 10^9 individual animals eliminated in around 1-2000 years when you take all the different species into consideration.

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I'll accept those numbers, although it should be noted that, if mammoths spread in a manner similar to elephants in Africa, I would expect much closer to the 10^7 number for them. Also, one expects the lower ranges on carnivores which, while not as large, need to eat from a much larger prey base.And yet, how many moa would you expect in such a lush environment as New Zealand, the size of Arizona? They're a tiny fraction of the size of mammoths. I think the only reasonable argument that you could make against them is that there was geographically less area for humans to fill, but that argument only lasts so long in a continental situation.Again, also, keep in mind that many populations are unstable once they get damaged (such as passenger pigeons proved to be).

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it strikes me that the blitzkrieg hypothesis is asking more from human hunters than they are capable of. How many humans are we talking about?

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Assuming a population growth rate of 4 births that make it to adulthood (in this environment without as many human diseases, with plentiful game) per woman, from a source of 10,000 people they could reach about 1e34 in 2000 years. Clearly birth rate isn't a problem - the issue is how much resources are there for people to survive on. Initially, there are vast resources. Consequently, one expects, in the absense of social memes preventing it, a population boom.

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And they didnt miss a single population?

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They missed Wrangel Island until about 6,000 years ago - I mean, that was the time of the Pharaohs. The fact is, they had tons of time to find all of the remaining populations. And again, I don't advocate overkill as being the only reason; just one reason.

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Worse, the overkill hypothesis ignores the fact that numerous species DIDNT disappear that would be as easy or easier to kill than mammoths, for example. Why didnt the American bison disappear? Too many of them? What about caribou, elk, mule deer, etc etc. These were harder to hunt than mammoth or ground sloth?

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Smaller animals in general survived the Pliestocene better than large ones. For many reasons, humans have historically prefered to hunt large animals when they are capable of it, whether for food, for ritual, or for sport. Also, needing to be explained by people who do not consider overkill as part of the cause of the extinction, is why the extinction was so heavily focused on large animals.

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Those few undisputed tool-marked bones could just as easily have been worked AFTER death: Clovis-as-scavenger vice Clovis-as-hunter.

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I'm familiar with the theory, but that wouldn't explain the massive spear points designed to be mounted on massive spears that have been found. Perhaps one might argue that they went after the young or sick, but they clearly were killing these massive animals.

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However, your belief that humans abruptly behaviorally adapted to a radically different lifestyle in spite of the fact that there remained a wide variety of prey species they could have continued to massively over-exploit requires even more assumptions than hyperdisease.

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Again, for the last time, I do *not* believe that it was an abrupt change - that's Mammothus's suggestion. I believe that it was steady natural selection. It sometimes feels like I'm debating with creationists here, and their "So why do these species changes just appear in the fossil record? Did the animals just suddenly decide to evolve?"

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However, it was an counterexample to your assertion that no species had ever gone extinct through disease not that this was a hyperdisease.

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That seems like a rather unfair argument. If the last Steller's Sea Cow had died of pneumonia, would we claim that pneumonia wiped out the species?

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but specifically the extinction of Bufo periglenes,

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Bufo periglenes once occupied a region only 4km^2 - hardly a stable species. To make matters worse, they had a very rain-sensitive breeding cycle. Their population crashed in 1987 due to unusual rainfall - only 29 toads were known to have survived out of 30,000.ADW: Incilius periglenes: INFORMATIONPlease name another species, preferably one that wasn't already essentially extinct.------------------
"Illuminant light,
illuminate me."

Good post. I just wanted to mention something:

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The idea of Homo Sapiens Sapiens taking out Homo Sapiens Neanderthalensis is ridiculous, the average Neandertal could have taken the average Sapiens and twisted him into a pretzel. With greater brain capacity and much greater strength, Neandertal had a huge advantage, thinking otherwise is simply pure sapiens arrogance.

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Quite true, the average neanderthal was stronger and far more resiliant than the average cro-magnon, although the greater numbers of our species per tribal group probably at least balanced that out, if not shifting it in our favor.However, on the brain capacity front, there are a number of animals that have larger brains than us - for example, most dolphins. However, when you study their brain under an MRI, you find a much simpler internal structure. The size of the brain isn't the most important thing when it comes to intelligence. Parrots are quite intelligent, and can learn things such as being able to recognize the difference between similar objects (size, shape, color, etc) and understand the concept of "names" for objects, and yet have tiny brains.If we could get a neanderthal brain, I would be all over that, it would really be facinating I write software that is used to study MRI images for a living. I bet there's lots of grad students that work in the lab here who would give their right arm (figuratively) to be able to write their thesis on that.One of the reasons that archaeologists suspect that neanderthals weren't as intelligent as homo sapiens sapiens is that their tools hardly evolved over the duration of their existance.------------------
"Illuminant light,
illuminate me."

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You are arguing polar opposites. You first argue that there are so many people around at this point in history that they can hunt down every last breeding pair of mammoths and multiple other species of megafauna yet are so sparsely distributed "scattered bands", that no evidence could possibley exist that they killed ALL of these megafaunal species.

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As I just stated, you can have 12 million people (plenty to kill off mammoth populations), and still have them be scattered bands. What is so difficult about this for you to understand? Are you expecting some sort of herd of 10 million mammoths all in one location? If so, that's preposterous, there never would be near enough food for them. The 25-60 million (depending on which estimate you use) buffalo in the early 1800s roamed through a good portion of the great plains in search of food. Were the indians all in one location when hunting buffalo? Did they leave these massive buffalo kill sites? What you're expecting to find goes completely against all evidence for human hunting in history.

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Hmmm, overill is critcized because of lack of evidence for what you and others "expect" to find yet I am not allowed to ask for evidence of mass hunting?

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1) I never once have criticized overill for a lack of evidence. Quite to the contrary, I wouldn't expect to find very much evidence for it even if it did happen.2) You're not allowed to ask for evidence for something that I'm not advocating. I'm not trying to claim that there was this big 12 million-person tribe that followed the mammoth around, and stampeded entire swaths of the herd off cliffs or whatnot (and then conveniently buried them, in easy-to-find locations, so that they'd preserve well).

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I suppose then that because of lack of evidence for 12 million human inhabitants in North America at the end Pleistocene that this is good evidence that they were there?

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NO! Can you be any more frustrating? It's like I'm debating with a creationist who keeps on saying "Well, if precambrian life was so widespread, where are all the fossils???" Again, I will ask, and I want a response this time: Please explain *Why* you would expect to find a sizable percentage of the human and mammoth remains from this brief time period to have been recovered. Cite examples of where this has occured elsewhere.Now, for the LAST TIME: The lack of evidence isn't evidence itself, and never once have I claimed that. The finding of a few sites (what, 15 kill sites) is what is expected.

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You keep repeating this and then are defensive about the fact that there is virtually NO evidence for the scenario.

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Apart from the fact that humans *have* caused megafauna extinctions in recent history through overhunting. So, in short, your claim falls to "it can't happen on a continent" and the unsupported "we should find more kill sites", despite all of the evidence that we *shouldn't* find more kill sites, and that we're lucky to have found the ones that we did.

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The culled elephants in Haynes studies were also collected for their ivory as Haynes notably leaves out of his comparison

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Try a better criticism, that hardly stands. Bones are not ivory. Where are the bones?Nice job with your quote, BTW - you literally pulled one out of the creationist playbook: starting a quote where a person points out a criticism of their theories, and cutting off where they go on to show how the criticism isn't valid.

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So, ivory collectors would have just left these culled elephants alone? They just dump the culled bones, don't burn them?

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Are you trying to claim that ivory hunters would take the time to burn the bones of the elephants that they hunted? If so, you're *really* stretching, Mammothus.

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i.e. in Siberia you can find huts constructed from mammoth bones, why not in North America where all of these Rambo killers should have been building skyscrapers with the excess of bone they would have had available?

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Are you talking about what *modern* people are building huts out of? If so, how is that relevant at all to this discussion?

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And note, you are now switching from the immense use the mammoth carcasses would have to Clovis people to they just killed the mammoths and dumped them for fun so that all evidence for them conveniently disappeared.

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How do you come to this conclusion? Name one place where I advocate that they just dumped the mammoths. I'm growing tired of these straw men. Are they intentional, or accidental?

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The skin I have in my freezer or the bone marrow?

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The preservation on that much-hyped mammoth has been, from what I have read, disappointing to say the least. And this is a mammoth that *wasn't* cut up, used as a shelter, and left to be pounded by the elements. I am rather shocked that you expect to find preserved shelters - and you have yet to explain why you feel that they would be preservedLet me turn your argument around: Where are the innuit artifacts through history? If you're expecting to find clovis shelters, there should be 10k years worth of innuit artifacts sitting in layers above them. Where are they all? You expect to find abundant clovis artifacts, so why not innuit?We find many clovis points, just as we find indian arrowheads. But we don't find indian shelters much at all. Again, though, you seem to have this weird notion that we should expect them to be preserved. Indians used bone tools, and all sorts of animal products. Why don't we find them abundantly preserved, like we do arrowheads?

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What assertion? I asked you to give an example and you claim it is my assertion..nice evasion there Mr. Williams

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No, that's not the case. I was referring to your claim that you have evidence that "suggests not". I'm calling you on that evidence. What are you saying that you asked for an example of?

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We describe the development of a polymerase chain reaction (PCR)-based approach for analysis of genetic diversity at the DQA loci in African Bos indicus and Bos taurus cattle.

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Good job, Mammothus! You showed that there's not a bottleneck in African cattle. Now can we get back to the North American megafauna situation?

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Previous DNA sequence analyses of several domestic species have suggested only a limited number of origination events. We analyzed mitochondrial DNA (mtDNA) control region sequences of 191 domestic horses and found a high diversity of matrilines.

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Great job again! Old-world horses don't have a bottleneck. Again, can we get back to the North American megafauna situation? Why are you putting in these ridiculous, unapplicable sidetracks?Concerning the moose:

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Divergence of nucleotide sequences of haplotypes with the 75-bp deletion (forming the American cluster on the phylogenetic tree) was the lowest (0.4%), which evidences respectively recent origin of the group of haplotypes

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Can you provide a link to the full text? BTW, a tight bottleneck isn't needed - just a reduction in population. Here's something I found on moose, which seems to indicate that there was a postcolonization bottleneck, at least among alaskan moose: http://www.bioone.org...
{Shortened display form of URL, to restore page width to normal - Adminnemooseus}

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The spectacular diversity in size, conformation, and pelage that characterizes the domestic dog reflects not only the intensity of artificial selection but ultimately the genetic variability of founding populations

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And now, we're back to old-world species...

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I can go on and on with this but can you provide a clear cut example of ALL surviving megafauna going through a genetic bottleneck?

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No. And you quite apparently can't show the opposite - thus, this point remains open to debate until better evidence can be provided. Let me know when you get your muskoxen data.

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And as I pointed out and you didn't address, Moas are about 1/23rd of the size of the Mammoths, and so would be expected to be much more stable in smaller populations.

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Any reference for this?

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Sure. The original numbers that I used were 515lbs for a large moa, and 12,000lbs for a small mammoth. I meant to compare a large moa with a large mammoth - the ratio is actually far worse if you do that.Moa sizes:45-550 lbs.
http://news.nationalgeographic.com/..._030911_moamating.htmlMammoth sizes: Columbian, 16,000-20,000 lbs; Wooly, 12,000-16,000 lbs.So, comparing maximum size animals of both types, we get about 36 times bigger for mammoths, and comparing minimum size animals, we get 227 times. Regardless, the Moa is a far, far smaller animal, and will consequently be expected to have a more stable population given a certain amount of land.

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Easy, on an island where are the refugia? Do you really think comparing and island population is identical to continental? If so why is there an entire subdiscipline dealing with island extinctions?

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An island the size of Colorado? Certainly, one would expect a faster extinction given the smaller land area, but seing as humans could cause an extinction of a (proportionally) small, common animal on such an area, why couldn't humans do it on a larger area? Where do you draw the line, between island and continent? Does Australia count as an island or continent?By the way, you didn't address my question: Do you not know who the Anasazi were? Because I referred to the environmental destruction wrought by the Anasazi and Easter Islanders, and then you stated that island populations are different - which makes me believe that you don't know who the Anasazi were.

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So Islands and continents are not different?

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There is no fundamental difference, only size. New Zealand is huge. So is Madagascar. Seing as there were no undesturbed continents left on Earth for us to study in the historic period, we can't witness, in real-time, a mass extinction on a continent, looking at what happened on the largest of islands is our best example.(by the way, when you quote something, please either italicize it ,quotation-mark it, put it in a quotation block, or otherwise distinguish it from your text)

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Where have you been suggesting a mixed approach?

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In Every Single Post!

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You have been claiming that absence of evidence for overkill is not harmful to the hypothesis, that my having any expectations of evidence is ridiculous,

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No. I have claimed that there is ample evidence of overkill in historic times even by "primitive" peoples, even on fairly large land masses, and named a bunch of other correlating factors that would tend to indicate that overkill was part of the extinction (different timings, by different peoples, in completely different regions, all resulted in the same result, for example). I cited that you don't need to hunt a species to extinction, only to weaken it to where it can't recover. I have stated that disease can play a part, either in finishing off a weakened species, or weaking a species so that other causes (such as hunting or habitat destruction) can take effect. What more do you want? The only region that I'm having to defend overkill is that you consider it to be *not* a factor, which is ridiculous given all of the observed incidents of overkill in history. You then put these preposterous levels of evidence that need to be recovered from the ground, ignoring the fact that we're talking about a very brief period, and things that one would never expect to preserve very well, across a massive expanse of land.

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Because you cannot have such a low population density AND wipe out all the megafauna and leave no trace.

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False. The population models for the Moa extinction (which concide with the arrival of the Maori people and the last remaining Moa fossils) indicate only 160 years growth from a seed population of 100 people, with pessimistic assumptions about the number of moas and the people's birth rate, and optimistic numbers about the Moa's birth rate. There's no huge population being discussed, and yet it obliterated the Moa in no time.Keep in mind: In the North American extinctions, while humans had a low population density, so did much of the megafauna (proportionally).

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15 sites with 50 bones that cannot even be distinguished from scavaging? A kill site cannot even be confirmed. Why do the tens of thousands of mammoth finds (mostly dating around the relevant time period due to preservation constraints) show natural death causes and not hunting? The ratio you ask for is overwhelmingly against overkill.

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Not around. *During* We've got a, what, 2000 year window here?So, if you think clovis points were for scavenging, be my guest. How such a tool would be relevant for a scavenger is beyond me.

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Yet you have dismissed every question I ask of you as purely stupid. That is what is insulting.

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What questions of yours have I not answered? There have been several that I have had to ask you multiple times.

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In any case, is there evidence of continental wide environmental impacts in the relevant areas for extinction? You yourself say they would have been very dispersed. So how would that support human environmental impacts causing such massive ecological trauma? I have yet to read anyone proposing this in the extincition literature for continents so I am wondering where you get your support for this scenario.

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If you alter the environment of part of a migration route, that's catastrophic. If you alter the balance of species in a region, that can have a catastrophic effect (for example, destroying the top predators, leading to a boom of herbavores). If you harvest certain types of plants only, you can change the flora of a region. There are many different ways which can have major effects. Also, you seem to believe one would expect that all human cultures, over all of the Americas, over all of the time of the extinction, to be identical, despite completely different environments. Why?

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I said prior to the end Pleistocene extinctions there was massive movement of animals between the continents and multiple mass extinction events.

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Are you claiming that there was an extinction prior to 12-14kya in recent geological history that was even comparable in size? Please, be more specific.

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There have been mass extinctions without humans on the scene as Quetzal also pointed out.

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I don't argue with this. However, the consistancy with which humans have caused mass extinctions of genera of large animals -directly or indirectly - wherever we have migrated to, is undeniable.

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And interesting that the little evidence for humans on Wrangel Island show they were a fishing culture...and in a place where mammoths are so well preserved that you can stumble over the bones in every river and they contain bone marrow and have skin, there is not a single butchered find.

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Once again, you're ignoring the time frame. Humans arrived and mammoths dissapeared at about the same time. You have to compare contemporary mammoth remains only, or you distort the picture. Why do you keep doing this? Also worth noting is how Wrangel Island sheds doubt on the climate change theory, since their mammoths survived. Wrangel Island is also only 2,000 square miles - smaller than Delaware. One would expect the extinction to be fairly quick, regardless of which model you use.

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No, I do not expect them to start farming. But then where would you get a number of 12 million? Is there a single nomadic purely hunting group that has ever reached a population size like this?

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I just use 12 million as an example number because it is the number Mithen uses in his hunting-only model of extinction. With a multiple cause theory, the number can be quite smaller.The number of Native Americans in the Americas when Columbus arrived is unknown, but from what I have read previously (I can try and hunt down the numbers), it was estimated to be between 40 and 90 million - roughly 2.5 to 5.6 per square mile.

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Oh yes, and the origin of the humans that entered the new world is not thought to have been the arctic but may have been in several waves and as far south as Mongolia so it is completely unclear that it was arctic adapted nomads who colonized Beringia and North America.

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This I've got to see...

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You familiar with the elephant seal or the cheetah? They suffered almost complete extinction and were able to bounce back. There has hardly been a megafaunal extinction since the end Pleistocene.

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The cheetah is in horrible shape right now, it has almost no genetic diversity. This is actually a case where a disease-caused extinction could likely occur, if it weren't for the dispersion of cheetahs to zoos around the world. Some animals bounce back better than others; notice how you didn't address the passenger pigeon despite it being brought up. Why couldn't various kinds of megafauna need to live in a sizable population, as the pigeons did?

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There has never been equilibrium

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How, exactly, are your cites supposed to suggest that there hasn't been a relative equilibrium when it comes to hunting cultural memes and prey adaptivity? If we're talking about moving back into an area where humans already are living, then they're going to be equally subject to fairly rapid selection factors if they overhunt. In the New World, it would take thousands of years for overhunting to catch up with them, because they can always just go elsewhere.

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Interesting that you argue this here but have no problem assuming it for the extinction of mammoths and all the megafauna throughout Europe all the way to Patagonia....and humans actualyl had contact with all of these animals long before the end Pleistocene extinctions i.e. cave paintings, 30,000 year old bone carvings in Siberia...so they had a really bad cycle..suddenly?

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Might I mention that we don't have any preserved siberian clothing, only needles carved from bone, in poor preservation? And yet, again, you are of the opinion that we should be finding worked hides or other similar pieces of evidence.Do you realize how vast and inhospitable Siberia is? It itself is about 5.2 million square miles. The coldest temperature recorded in the Northern Hemisphere is Verkhoyansk, with -96 F. While there is a brief growing season in the summer, and some regions are forested, the area as a whole is frigid and bleak. Due to this, it took humans almost 20,000 years to reach the Bering Straight. Clothing pretty much had to be invented by humans, in addition to other things needed to survive such frigid weather.If they haven't made it to a location yet, how do you expect them to cause animals to go extinct in it?

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What is the negative selection agianst the natives?

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Natives are selected against if they destroy their own food supply or other cultural requirements, just as the Anasazi were.

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Co-evolution is not enough as any mutation/behavior that provides an advantage should spread rapidly...

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Yes. But we had cultures filling up an entire continent here. Even if those who remained in Alaska reached a relative steady-state, it won't have any effect on those who are by then pushing down to Mexico. The Maori eventually reached a steady state too, you know.

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why would they not have recognized their own land of plenty..especially if you argue that there were cycles where they did? What would have brought them back to not doing it?

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I said that it is possible for a culture in a (relative) steady state to go back to a destructive mode - social memes change, after all. But if they do, they themselves will be selected against.

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Why is there no evidence that they did do it?

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Do you realize that you've been parallelling the "God of the Gaps" theory this whole time? My argument is from evidence of hunting to extinction and severe environmental destruction by primitive tribes in recent history on quite large land masses, but you are focusing on a lack of evidence - for or against - in the past, where preservation is quite poor and not expected very often, and we're looking at a very brief time frame.

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Also African culture is not monolithic. There are some groups that hunt elephants, others that do not. You cannot tell me that hunters in the Congo are anything like the !Kung

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And, for the most part, each of these different cultures has been in a relatively steady state with their flora and fauna.

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How do you come to the conclusion that they learned in *one generation*?

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from the paper I cited "Although prey that had been unfamiliar with dangerous predators for as few as 50 to 130 years were highly vulnerable to initial encounters, behavioral adjustments to reduce predation transpired within a single generation. "

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Ah, my mistake, I didn't realize that you were referring to that paper. So, what "behavioral adjustments" do you suggest that they make to avoid humans? It's no simple task. Of course, I put the greater burden on the human side - what the humans tend to hunt, how they tend to hunt, how wasteful they are, what age/sex they target, how much of their diet is based on hunting vs. gathering, etc.(skipping a number of already addressed points)

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Actually, I would expect them to be harder, because they won't preserve as well.

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Interesting then that many major mammoth finds are in places in the US that are not permafrost. Actual habitation would be easier to find in non permafrost since the tundra tends to shift around so much that you never find fossils intact and the layers get mixed so that you cnanot do stratiography...not so outside the tundra.

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This was in a discussion about shelters, so we're mostly talking about skin. How much skin has been found outside of the tundra?

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Those of us who do not view the end Pleistocene extinctions as a closed issue are trying to find out...Peter Dazsak is doing this type of research for modern extinctions. Exactly how much do you really think is known about extinction in any case?

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Very few would consider this a closed issue, myself included. However, judging from what we have observed of extinctions in history, overkill seems likely to be at least part of the cause. Let me know when you come into any evidence that, unlike overkill, overill has led to the extinction of a healthy species at any point in recorded history.

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When has there been an equivalent situation to the end Pleistocene regarding immunlogically naive species?

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Many, many islands.

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There is somne evidence that Xmas Island rats went extinct by introduction of pathogens from ship rats..we are doing the molecular work now..

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If you can manage to get such groundbreaking results, let me know. Until then, overill is really in tatters if you look at the historical record - we're only talking about disease wiping out species that were near extinct anyway.

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there is also evidence that the thylacine was brought down by disease and not purely by hunting...

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What, a combination of factors, which includes hunting? Guess whose position you just advocated there.

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Why would they not be on this scale?

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Because there were no more highly inhabited 16 million square mile land masses after that, quite obviously.P.S. - So, Mammothus, how do you propose that extinction-causing hyperdiseases followed every major human migration into uninhabited territory, despite time or location, throughout history?------------------
"Illuminant light,
illuminate me."[This message has been edited by Rei, 10-21-2003][This message has been edited by Adminnemooseus, 10-21-2003]

You know, Quetzal, I'm not sure why we're debating here - we actually seem to agree on most issues related to this. My view is that many issues, of which hunting was one, led to changes in the flora and fauna in various regions, which in turn caused other species to decline. Some species weren't lucky enough to be able to recover. I assume that this is what you mean by your "disequilibrium" hypothesis.I don't disagree that disease can have a strong impact. What I disagree with is the notion that a disease or family of diseases have followed every major human migration into areas that haven't seen humans before in history, in different time periods and geographical areas, and taken a diverse, large group of otherwise healthy animals, from completely different orders, and brought them to extinction each time. That really seems like a preposterous concept to me, not something that has been observed in the world. Can diseases weaken a population? Yes. Can diseases kill off an already severely weakened population? Yes. Can diseases alone cause what is witnessed at the end of the Pliestocene? Very doubtful.My main gripe with Mammothus on this front is that he seems insistant that killing had nothing to do with it. I disagree. The weapons used by the clovis culture weren't those of scavengers - they were those of hunters of large game. They had an entire continent to expand into, and plentiful food. It is only reasonable to expect a population boom. Is hunting the only reason? Of course not - the extinctions are too diverse for that. But hunting clearly is going to play a major impact on the environment itself. I also think it's preposterous to expect major amounts of preservation from such a brief time period 10kya.I hate the unreasonable belief that native cultures were somehow all in touch with the environment, and only modern humans have become destructive. It's not evidenced by history.P.S. - I still think it was unfair of you to pull out the second sentence of my first paragraph and hold it up alone, even though the sentence right after qualifies it. But that's beside the point.------------------
"Illuminant light,
illuminate me."

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Well, I'd say we're debating because of your insistence that human hunting - while perhaps not the ultimate cause - was in fact a major proximate cause of the extinctions.

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If you want me to quantify it, I'd put it at about 20-30% relevance.

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Your assertions concerning the ability of paleoindians to effect mass destruction of continent-wide populations of megaherbivores and (indirectly) their predators is unsupported, and I think unsupportable.

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Not just killing of herbavores, and indrectly causing their predators to die off. Killing of both predators and herbavores, in addition to altering the flora; this indirectly causing instabilility which leads to more die-offs, and this in turn leading to more instability... etc, until a new steady state can be reached.

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You're also using an inappropriate analogy of island extinctions (or the destructive practices of restricted populations such as the "Anasazi") to extrapolate to the wider continents-wide hecatomb of literally millions of organisms in a very brief period which is contraindicated by the available evidence.

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1) I'd hardly call around a hundred kilometer radius "restricted".
2) I'm not saying that the entire continent was deforested. It was just an example of continental populations causing local environmental destruction.

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Finally, your argument concerning behavioral/cultural (meme) evolution in paleoindians has not been well-developed (in this case, you need to provide more detail on the argument, including what evidence might lead one to suspect that this occurred). That is why we are debating.

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Well, in the case of the Anasazi (an easily documented example), wouldn't you say that they were selected against, while the Pueblo were selected for? Also, what model would you propose for memes not having an effect?

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Mammuthus certainly isn't.

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Then I would like clarification from Mammothus on just what he's advocated. Despite being continually pigeonholed into "overkill-only", I have in virtually every post explained that I do not consider overkill-only to be the cause, but instead a variety of factors (of which overkill is one: overkill, overill, overharvest, overlogging, climate change, introduced species, and the ramifications of all of these magnified through disequilibrium).

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The only potential example for this is the highly selective extinction event that occurred in the Late Pleistocene.

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Highly selective? Unless your selection criteria is "large", I don't know how you come to this conclusion. On a quick search, 95% of large herbivores (>2 tons), and 73% of genera of animals weighing 44kg or more, went extinct in North America.

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Since the former's preferred habitat was the juniper scrublands of the American southwest and Mexico, I find the lack of remains associated with the known kill sites in the area to be problematic. ... Only Martin's blitzkreig takes it as a given that no evidence will be found because of the speed of the process

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While some dates are still up in the air, it *does* appear to have been a very fast process, whatever killed them; in Europe, and Asia, it doesn't. And the key issue concerning whether the amount of evidence is what is expected or not is the speed; all debate on this topic hinges on that.P.S. - why do you keep putting "Anasazi" in quotes? Would you rather I refer to them as "ancestral Puebloans"?------------------
"Illuminant light,
illuminate me."

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You care to provide evidence for this assertion?

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What are you thinking is preventing such a population? The Americas had notably more Native Americans than that when Columbus arrived, so it clearly could support that many *without* the megafauna. Do you think population density is a problem? Hardly, that's less than one person per square mile. Do you think transportation times are a problem? Hardly - not only do we find plenty of evidence that they *did* travel down the coast to southern South America in short time, but the distance - 10,000 miles - would be only 5 miles per year (a tiny rate, really), given 2,000 years (yes, I know about how the Monte Verde is dated to 12,500, but we're going to just operate on the figures being used: 2,000 years to populate the continental *interiors*, as opposed to just the coast). Do you think growth rates are a problem? Hardly - using simplifying assumptions (a growth rate of 4 children that survive to adulthood per woman, assuming they're all born at age 20 and then the woman and her husband dies, etc) so that I can calculate quickly, in 2000 years you would have 100 doublings of the population, so an initial crossing of 1,000 people would reach 1.3e33 people if given infinite resources and infinite land. Clearly biological constraints for reproduction aren't a problem here, the issue is resources - how many people are there resources to provide for. Which was the first point addressed.

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Nope, I expect exactly the opposite. Mammoth fossil distribution spans several continents for this time period.

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Which is exactly what I'm saying: With the mammoths spread out, the humans will be spread out as well - I.e., small bands, even though the total population would be high. Are we clear on this now?... You know, these are getting longer and longer. My last response took something like 2 hours, and this one may end up being even longer. I really don't have time for this today, I'll try and catch up tomorrow.------------------
"Illuminant light,
illuminate me."