Overkill, Overchill, Overill? Megafaunal extinction causes

What caused the end Pleistocene megafaunal extinctions?
This is a spin off topic from the Neanderthals thread in the Human Origins forum.

Hi Mr. JWhat were the hypothesized other hunters? Why are there so few sites supportable as kill sites?

However, it is doubtful that sabre toothed cats would have had much of an impact on mammoth populations. They might get lucky and pick of a few juveniles separated from the herd or isolated males in a weakend state but much like modern elephants, it is doubtful mammoths had serious natural predators other than humans.

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I don't really see why kill-sites (meaning a site showing the remains of vast numbers of prey species, yes?) are expected. A Mammoth carries a lot of food, so I would expect killing individuals and moving to the corpse to be a sane strategy for nomadic tribes peoples.

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This would be a sane strategy but it is not what is proposed by overkill. If human hunters killed a couple of mammoths each season you would not expect kill sites..on the other hand you would not expect mammoths to be extinct either. If humans slaughtered all the mammoths across all of Asia and America you would expect to find kill sites because it would have required massive slaughter of a massive number of animals over a short period of time.[This message has been edited by Mammuthus, 10-15-2003]

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Mammoths are by no means the only mega fauna of the age. I think it's highly likely that the very large carnivores that lived in the same period as the very large herbivores ate said herbivores. Otherwise I can see no explanation for their also increased size. I was also under the impression that adult mammoth remains had been found with teeth marks consistent with those of sabre-tooth tiger, although this might have been after-death scavenging.

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No, they were not the only megafauna. But they were a keystone species and there is precious little evidence that they had natural predators. The large size of elephantids, and tusk size in mammoths in particular, is better explained by sexual selection as opposed to predator avoidance. Elephantid size variation is rather pronounced and does not seem to correlate with presence or absence of predators.
There is evidence of sabre-tooth killing of mammoth babies. Like with both living genera of elephants males once they reach puberty get booted from the group (which consists of adult females and juveniles). They then go off and either form bachelor male groups or wander by themselves. (This was also likely the case for mammoths). Individual males in a weakened state might be susceptible to predation but elephants in groups would not. Taking an occassional juvenile or weak and injured male mammoth would not consitute full scale predation and there is no evidence for any predator that would specialize on mammoths. Hard to imagine predators of a highly intelligent, massive, group living herbivore other than humans.

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I'm not advocating the overkill hypothesis.

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I just try to bash overkill any chance I get

Nope. I prefer a combination of introduction of novel pathogens by the newly invading species (not just humans) affecting keystone species such as mammoths along with climate change allowing for faster breeding herbivores to outcompete keysoone species into extinction. Absence of the keystone species would have drastically changed the ecology in their former habitat which may have resulted in even more exinctions including sabre-tooth etc which also had competition from other carnivores who may have been better at switching prey.The appeal to me of pathogens is not necessarily that it has to be correct but at least one can potentially collect evidence for introduction of novel pathogens that correlates with the arrival of humans. Positive supporting evidence does not seem to be available for overkill. Climate change as a singular cause of end Pleistocene mass extinction is also full of holes.

I'm glad we cleared that up so quickly

Bacteria were not ruled out, but there are number of problems in searching for them from ancient materials not associated with viruses. For example, there are a lot of free living forms related to pathogenic forms so getting a funny bacterial sequence does not mean it is not a soil contaminant. Also, I could go outside, take some soil, prep DNA and sequence and find unknown species of bacteria. What do you do with an ancient sample where you find uknown bacteria when you cannot classify the modern ones? Also the dynamics of viral infections seemed more appropriate for a hypervirulent pathogen than a bacterial pathogen...It also depends on what tissues you can get.. With mammoths it is not so bad. Most is bone, but I have bone marrow, skin, brain, lung, heart, you name it from some samples....in any case, I can say so far nothing has worked ...it would probably help if I was not doing all of this a side project to a side project I have met with Paul Martin several times. He is a really nice guy and really smart...even when people disagree with him...his latest idea is to introduce elephants back into the wild in the U.S. since they were there before.

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

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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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There are thousands upon thousands of mammoth fossils found everywhere from Europe to Mexico and yet only a few agreed upon kill sites. Evidence of human settlement such as Clovis suggest there were not a whole hell of a lot of people around so each person would have to kill a lot of megafauna to make any dent in the population much less provoke extinction. Why are there so few kill sites?

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

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

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I am more surprised that people immediately assume that all cultures will be completely wasteful and destructive...even without evidence. The population boom does not have evidence. There is also little evidence that the end Pleistocene environment was in equilibrium. Dramatic climatic changes were occuring. 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. 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? I find overkill a poor explanation for the complete extinction of Pleistocene megafaunal species.

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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.

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There are a lot of viruses and bacteria that can jump among species and cause mass die offs. 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. And I never said it was a singular cause...a hypothetical important one where we have a chance (in theory) to gather evidence at the molecular level but not a sole cause. Overkill has not produced almost any postive evidence. Climate change is still being worked on...it is still up in the air but I think overkill is the weakest.

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Things like maximum effects in the areas affected the least by ice age man, many animals wiped out in the new world survived in the old world. Generally man is pointed to as being the carrier of some super 'bug' that could wipe out huge animal populations and yet it didn't harm man or the animals in other areas. Modern man shows no traces of this super bug, and there is no record in history of new species being wiped out by a human carried disease upon discovery. This super bug also left no trace of itself in fossil evidence such as bone scarring, poor health, slow growth, deformity, etc, and so far DNA testing of modern populations and ice age remains has turned up no trace of it at all. Admittedly finding the DNA bug would be very hard, but the complete lack of evidence and considering the conflicting evidence, the 'overill' theory sounds to me like a flight of fancy that flies through the air without any support at all.

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Hi wmscott,
Thanks for the post. I was afraid this thread might become extinct Let me address a few of the issues you brought up the best I can. The keystone species of interest, i.e. mammoths did not survive anywhere (except Wrangel Island) after about 9,000 years ago. I am interested in the animals that survived nowhere after the end Pleistocene. Humans are also not necessarily predicted to be the carrier of the bug (or bugs). However, as you point out, they would have to have co-evolved with the pathogens in order not to be suceptible. It is more like a typhoid Mary effect of humans, their commensals, whatever parasites they were bringing with them, laying waste to immunologically naive megafauna with slow population growth due to long gestation time being a huge disadvantage for them. Many pathogens do not leave any trace evidence such as deformities or scarring in bone. A few do and there is a group trying to isolate Mycobacterium from bovid fossils. As to DNA testing of fossils, outside of the group I worked for a few years ago, nobody else was doing it...so there were two people (me and my tech) working on substandard materials for two years on a hypothesis that was proposed in 1996. I know it is a bit of a lame excuse, but the number of people going after pathogens relative to those studying climate and overkill makes it a bit premature to write off the chance of gathering supporting evidence.

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I favor a variation of the 'overchill' theory, a run away deglaciation event that resulted in a temporary rise in sea level that resulted in wiping out many animals, or as it is more commonly known as, the biblical flood (minus all the absurd YEC theories of course). Whereas the 'overill' theory has no supporting evidence, there is evidence that supports a recent flood of global proportions. Much of this evidence has already been extensively discussed in the "Solving the Mystery of the Biblical Flood" threads, and while you are still looking for your smoking gun, I have already found mine. I can look through my microscope and see marine diatoms left behind by a recent very large marine transgression. This puts a recent global flood ahead of the 'overill' theory in terms of supporting evidence. A late Ice Age flood also has the advantage of more easily accounting for the patterns seen in the die offs, considering the effects large floods have on the types of animals that are killed and those that tend to survive.

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However, why was climate change (from everything I have heard) asynchronous throughout that period yet extinctions simultaneous? Why would mammoths in Montana be wiped out by a flood but humans survived. Why did mammoths survive on Wrangel Island yet a stones throw away in Siberia they went down? Why did muskoxen and buffalo survive? A global flood should have affected African megafauna (or Indian-southeast Asian) but it did not (or at least not to the extent of the areas where humans and their commensals showed up). I think there are a lot of climate change flaws you may be overlooking.I like the climate work and think it is worthwhile because one can formulate testable hypotheses based on it (and it is itself testable and falsifiable ultimately). Overkill, which I am glad we agree on, is lacking evidence but even finding evidence that is reliable is a challenge since markings on a bone do not mean the animal was hunted by humans. As to overill, while I will fully admit that we were unable to generate positive molecular support, it was the result of a pilot study..and biomolecular-wise, my experiences with mammoth (and other extinct megafauna) is that between 0-30% of the best preserved samples have any DNA at all. So the challenge is immense but still warrants further work before writing off pathogens completely.cheers,
M

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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?

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

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http://www.dreamwell.com/ali/anthro/mammoth.htm

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They 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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Here are some more recent studiesProc Natl Acad Sci U S A. 2002 Nov 12;99(23):14624-7. Epub 2002 Nov 04. Related Articles, LinksExplaining the Pleistocene megafaunal extinctions: models, chronologies, and assumptions.Brook BW, Bowman DM.Key Centre for Tropical Wildlife Management, Northern Territory University, Darwin 0909, Australia. barry.brook@ntu.edu.auUnderstanding of the Pleistocene megafaunal extinctions has been advanced recently by the application of simulation models and new developments in geochronological dating. Together these have been used to posit a rapid demise of megafauna due to over-hunting by invading humans. However, we demonstrate that the results of these extinction models are highly sensitive to implicit assumptions concerning the degree of prey naivety to human hunters. In addition, we show that in Greater Australia, where the extinctions occurred well before the end of the last Ice Age (unlike the North American situation), estimates of the duration of coexistence between humans and megafauna remain imprecise. Contrary to recent claims, the existing data do not prove the "blitzkrieg" model of overkill.Here is a pro overkill paper by the most over the top human only guy there isScience. 2001 Jun 8;292(5523):1893-6. Related Articles, LinksErratum in:
Science 2001 Sep 21;293(5538):2205.Comment in:
Science. 2001 Nov 16;294(5546):1459-62.A multispecies overkill simulation of the end-Pleistocene megafaunal mass extinction.Alroy J.National Center for Ecological Analysis and Synthesis, University of California, 735 State Street, Suite 300, Santa Barbara, CA 93101, USA. alroy@nceas.ucsb.eduA computer simulation of North American end-Pleistocene human and large herbivore population dynamics correctly predicts the extinction or survival of 32 out of 41 prey species. Slow human population growth rates, random hunting, and low maximum hunting effort are assumed; additional parameters are based on published values. Predictions are close to observed values for overall extinction rates, human population densities, game consumption rates, and the temporal overlap of humans and extinct species. Results are robust to variation in unconstrained parameters. This fully mechanistic model accounts for megafaunal extinction without invoking climate change and secondary ecological effects.What part of the critique do you feel is important to the discussion?

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), and the climate is just one of many factors, it itself isn't that major

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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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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 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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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.

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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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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. 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. Why would animals as intelligent as elephants be so slow to realize when something is dangerous? There is even counter evidence that shows that less intelligent animals than elephants can learn novel predator avoidance in a single generationScience. 2001 Feb 9;291(5506):1036-9. Related Articles, LinksComment in:
Science. 2001 Feb 9;291(5506):997-8.Recolonizing carnivores and naive prey: conservation lessons from Pleistocene extinctions.Berger J, Swenson JE, Persson IL.Program in Ecology, Evolution, and Conservation Biology, University of Nevada, Reno, NV 89512, USA. berger@unr.eduThe current extinction of many of Earth's large terrestrial carnivores has left some extant prey species lacking knowledge about contemporary predators, a situation roughly parallel to that 10,000 to 50,000 years ago, when naive animals first encountered colonizing human hunters. Along present-day carnivore recolonization fronts, brown (also called grizzly) bears killed predator-naive adult moose at disproportionately high rates in Scandinavia, and moose mothers who lost juveniles to recolonizing wolves in North America's Yellowstone region developed hypersensitivity to wolf howls. 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. The fact that at least one prey species quickly learns to be wary of restored carnivores should negate fears about localized prey extinction.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? 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? 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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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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Pollack JD. Related Articles, Links
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Trends Microbiol. 2001 Mar;9(3):108.J Gen Virol. 2003 Sep;84(Pt 9):2285-92. Related Articles, LinksThe origin of the 1918 pandemic influenza virus: a continuing enigma.Reid AH, Taubenberger JK.Division of Molecular Pathology, Department of Cellular Pathology and Genetics, Armed Forces Institute of Pathology, 1413 Research Blvd, Building 101, Room 1057, Rockville, MD 20850-3125, USA.Influenza A virus is a major public health threat, killing more than 30,000 per year in the USA alone, sickening millions and inflicting substantial economic costs. Novel influenza virus strains emerge periodically to which humans have little immunity, resulting in devastating pandemics. The 1918 pandemic killed nearly 700,000 Americans and 40 million people worldwide. Pandemics in 1957 and 1968, while much less devastating than 1918, also caused tens of thousands of deaths in the USA. The influenza A virus is capable of enormous genetic variability, both by continuous, gradual mutation and by reassortment of gene segments between viruses. Both the 1957 and 1968 pandemic strains are thought to have originated as reassortants, in which one or both human-adapted viral surface proteins were replaced by proteins from avian influenza virus strains. Analyses of the surface proteins of the 1918 pandemic strain, however, suggest that this strain may have had a different origin. The haemagglutinin gene segment of the virus may have come directly from an avian source different from those currently circulating. Alternatively, the virus, or some of its gene segments, may have evolved in an intermediate host before emerging as a human pathogen. Determining whether pandemic influenza virus strains can emerge via different pathways will affect the scope and focus of surveillance and prevention efforts.It should be noted that at the time of the 1918 flu pandemic, millions of pigs died from the flu as well.here is flu able to jump from birds to ferretsJ Virol. 2002 May;76(9):4420-9. Related Articles, LinksPathogenesis of avian influenza A (H5N1) viruses in ferrets.Zitzow LA, Rowe T, Morken T, Shieh WJ, Zaki S, Katz JM.Influenza Branch, National Center for Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia 30333, USA.Highly pathogenic avian influenza A H5N1 viruses caused outbreaks of disease in domestic poultry and humans in Hong Kong in 1997. Direct transmission of the H5N1 viruses from birds to humans resulted in 18 documented cases of respiratory illness, including six deaths. Here we evaluated two of the avian H5N1 viruses isolated from humans for their ability to replicate and cause disease in outbred ferrets. A/Hong Kong/483/97 virus was isolated from a fatal case and was highly pathogenic in the BALB/c mouse model, whereas A/Hong Kong/486/97 virus was isolated from a case with mild illness and exhibited a low-pathogenicity phenotype in mice. Ferrets infected intranasally with 10(7) 50% egg infectious doses (EID(50)) of either H5N1 virus exhibited severe lethargy, fever, weight loss, transient lymphopenia, and replication in the upper and lower respiratory tract, as well as multiple systemic organs, including the brain. Gastrointestinal symptoms were seen in some animals. In contrast, weight loss and severe lethargy were not noted in ferrets infected with 10(7) EID(50) of two recent human H3N2 viruses, although these viruses were also isolated from the brains, but not other extrapulmonary organs, of infected animals. The results demonstrate that both H5N1 viruses were highly virulent in the outbred ferret model, unlike the differential pathogenicity documented in inbred BALB/c mice. We propose the ferret as an alternative model system for the study of these highly pathogenic avian viruses.and good old rabiesG Batteriol Virol Immunol. 1979 Jan-Jun;71(1-6):47-54. Related Articles, Links[Routes of spread of the current rabies epizoonosis in Europe][Article in Italian]Pugliese A, Croce F.The present report describes the spreading paths of the rabic epidemic that is rapidly reaching Italy from Central Europe. The epidemiologic situation of neighbouring countries is examined and the sanitary measures undertaken in Europe against epidemic are compared.

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You've certainly implied it.

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Close, but that ain' me He writes way better...remember I am a molecular biologist..not a paleo...More seriously, in terms of gathering evidence, it is effectively useless to say lots of things contributed everyroup tries to test for evidence supporting their hypothesis and eliminate as many variables as possible. I am sure the end Pleistocene extinctions had multiple causes like everything else in nature. We can either support or eliminate potential candidates by doing research. The overkill guys like Alroy don't want anyone to do the research and just accept overkill.

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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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Ok, so first you say small bands of nomads living in tents but then immediately below

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

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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? 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?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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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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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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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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It is relatively small compared to the area from Europe to Mexico where every single last one of the largest megafauna became extinct.in any case here is a referenceECOLOGY
Sporormiella and the late Holocene extinctions in MadagascarDavid A. Burney * , Guy S. Robinson * and Lida Pigott Burney **Department of Biological Sciences, Fordham University, Bronx, NY 10458; and The Louis Calder Center Biological Station, Fordham University, P.O. Box K, Armonk, NY 10504Communicated by Henry T. Wright, University of Michigan, Ann Arbor, MI, July 24, 2003 (received for review January 25, 2003)Fossil spores of the dung fungus Sporormiella spp. in sediment cores from throughout Madagascar provide new information concerning megafaunal extinction and the introduction of livestock. Sporormiella percentages are very high in prehuman southwest Madagascar, but at the site with best stratigraphic resolution the spore declines sharply by 1,720 yr B.P. (radiocarbon years ago). Within a few centuries there is a concomitant rise in microscopic charcoal that probably represents human transformation of the local environment. Reduced megaherbivore biomass in wooded savannas may have resulted in increased plant biomass and more severe fires. Some now-extinct taxa persisted locally for a millennium or more after the inferred megafaunal decline. Sites in closed humid forests of northwest Madagascar and a montane ericoid formation of the central highlands show only low to moderate Sporormiella percentages before humans. A subsequent rise in spore concentrations, thought to be evidence for livestock proliferation, occurs earliest at Amparihibe in the northwest at 1,130 yr B.P.And in fact for moa extinctions habitat destruction is considered just as plausible as huntingHoldaway RN, Jacomb C. Related Articles, Links
Rapid extinction of the moas (Aves: Dinornithiformes): model, test, and implications.
Science. 2000 Mar 24;287(5461):2250-4.

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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.

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In short, they were selected against.

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Which shows how different an island is from continental populations.

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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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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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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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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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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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So all of Europe to Mexico, where most of the megafauna that went extinct was concentrated, was artic? If this was the case humans would never have spread anywhere. It was precisely this retreat of the arctic that allowed for the spread of humans and other animals into north America. Nothrotheriops in Arizona was not living in the arctic...and Mammuthus columbi was not either. 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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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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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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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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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? 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 pressureMol Ecol. 2002 Dec;11(12):2489-98. Related Articles, LinksPatterns of molecular genetic variation among African elephant populations.Comstock KE, Georgiadis N, Pecon-Slattery J, Roca AL, Ostrander EA, O'Brien SJ, Wasser SK.Clinical Research Division, Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue N, D4-100, Seattle, WA 98109-1024, USA.The highly threatened African elephants have recently been subdivided into two species, Loxodonta africana (savannah or bush elephant) and L. cyclotis (forest elephant) based on morphological and molecular studies. A molecular genetic assessment of 16 microsatellite loci across 20 populations (189 individuals) affirms species level genetic differentiation and provides robust genotypic assessment of species affiliation. Savannah elephant populations show modest levels of phylogeographic subdivision based on composite microsatellite genotype, an indication of recent population isolation and restricted gene flow between locales. The savannah elephants show significantly lower genetic diversity than forest elephants, probably reflecting a founder effect in the recent history of the savannah species.

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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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Interesting then that moose (the only animals tested thus far) learned in one generation to avoid predators. And there still is not clarification as to what the selective pressure was against overhunting considering buffalo and cervids (smaller ones) were expanding in population size as mammoths and other giant grazers were disappearing.

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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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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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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".

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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. Human populations would be expected to exhibit behaviors conducive to their survival. Hunting a food source to extinction is not particularly compelling. Especially as the prey source declined and it takes more energy to find let alone kill the prey, there would be intense pressure to switch prey. As we see from elephant seals, if you leave a species alone even for a short while they recover..it is not easy to drive things to extinction....what would have been the selected behavior to hunt every single last mammoth down instead of turning and slaughtering all the buffalo which they did not.

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Once again, and hopefully for the last time: Large animals have smaller numbers, and consequently less stable populations.

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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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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...

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

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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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Alroy also thinks we should not even start hunting around for pathogens since obviously it had to be overkill disregarding the complete lack of evidence. And you seem to be indicating that finding supporting evidence for overkill in the form of kill sites would be detrimental to the hypothesis?I am not wedded to any particular hypothesis...but just like creationism, I am not going to accept things merely because someone tells me they are right. I want evidence..especially if I am going to be addressed like a stupid ass. If the overkill guys come up with a ton of rock solid evidence and I am convince..great...then I have one less project to worry about. If the climate guys can fill in all the holes and contradictions in their hypothesis..ditto. If I cannot find any pathogens or find data exactly contradicting the overill hypothesis, then it is history. But at this point I think overkill is just as badly supported as overill.

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

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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. 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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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.

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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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I am astounded that work as important as yours is so severely neglected and underfunded. I think you are probably barking up the wrong tree, but how will we ever know unless you are able to find out? I would very much like to see your work completed, I would like to know if you are right or not.

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Hi wmscott,
Thanks for the encouragement. I don't feel particularly put upon. I did successfully get money a couple of times from private donors and from the NSF. But we never had a big enough operation to go thoroughly through all the fossils. This may happen in the future though as a couple of other ancient biomolecule groups have been sounding interested lately.

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On the problem of climate change being asynchronous throughout that period yet extinctions were simultaneous, a sudden abrupt large rise in sea level would of course be simultaneous all over the world. Simultaneous extinctions are easy for a flood model to deal with, the problem is with progressive extinctions that are believed to have occurred over time towards the end of the ice age. But we must be careful not to over simplify, before the flood event there may have been other factors at work, perhaps even your super bug, that may have caused a number of extinctions.

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How would a flooding model explain the expansion of the grasslands in North America and the increase in population size of several other species of herbivore such as buffalo and several species of cervids?

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There may have been smaller abrupt changes in sea level leading up to the big one, that caused some extinctions in animals who's habit was limited to low elevations. Plus we have to remember that there is some noise in the data and what may appear to have been asynchronous may have been simultaneous.

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There is a lot of noise in the data to be sure. However, Wrangel Island is particularly vexing. The bones date from anyhere between 20 and 30 Kya to 4.5 Kya whereas just a few km away in Siberia the record stops at 9.5 Kya. This suggests the climate change was asynchronous.

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The surviver problem is solved by remembering that there would have been scattered 'islands' of survival. North America seems to have been particularly hard hit, many of the large animals that we have today are actually recent arrivals from the old world.

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For some species such as muskoxen that is correct. They apparently survived in isolated refugia. But buffalo and most cervids did not and to my knowledge, there is no evidence of a genetic bottleneck at this time.

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The ice age humans didn't do any better, take a look at the difference between ice age skulls and modern populations in those same areas, the modern populations are nearly always the result of later migration. As demonstrated by the complete lack of Neandertal survival and complete lack of even their DNA in modern populations, there was a human bottle neck as well. The extinction event hit the hunters as well as the hunted, which throws a monkey wrench into both the overkill theory and the 'overill' theory as well.

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A problem with using neandertals as an example is two fold 1) the evidence is very thin that there was no interbreeding (see my arguments in the Neandertal thread) 2) All neandertal fossils studied to date predate the end Pleistocene extinctions by about 20 K years. So whatever happened was in Europe and independent of the end Pleitocene megafaunal extinctions.The origin of the human genetic bottleneck is unknown but I do not believe it dates to the appropriate time period i.e. end Pleistocene. If anything, H. sapiens was an expanding population at that time.In any case, all three hypotheses are full of holes currently which makes both research and debate rather interesting.

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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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Deliberately being like what? 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. Either the density was high enough for them to hunt the megafauna to extinction in which case one would expect to see evidence of such pervasive hunting or the density was much lower which provides no logical way that so few people would have killed off so many animals in so short a time.

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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.

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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? 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? Don't you see that you are supporting a hypothesis that only thrives on LACK of evidence. You keep repeating this and then are defensive about the fact that there is virtually NO evidence for the scenario.

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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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15 sites with 50 mammoths and this is the sum total evidence that 12 million people inhabited North America and caused the extinction of the megafauna at the end Pleistocene. Do you really find this compelling? Case closed, Alroy can send us all home? Would you accept such tenuous support if it were a hypothesis you did not like? The culled elephants in Haynes studies were also collected for their ivory as Haynes notably leaves out of his comparisonHaynes first "Clovis mammoth sites are supposed to be rare. I think we can refute that pretty easily. I think Paul Martin originally, in his talk here, said something about something that I've told him, that there have been thousands and thousands of elephants killed -- not only in clearing of land for agricultural use, but in culling operations. In 1984, '85 and '86 I saw 9,000 elephants culled, and I cannot find a single site anymore of their bones -- within 10 to 15 years they're all gone. And I saw this happening within three months of every year, over those three-year periods."...but then"Now, let me go to my Zimbabwe work, to my own fieldwork, because that's the viewpoint I can tell you the best, or the most about. Most of what I have produced seems to be used to support the climate-change-only model of explaining extinction. Now, admittedly, a lot of it actually does point that way very clearly. For example, if you look at the mammoth sites in the fossil record, and you look at modern elephant sites -- the ones that have been documented during culling or other noncultural death events -- they look very much alike. The same kinds of age profiles are represented in the fossil and the modern elephants; the same kind of geomorphic locations -- not at big rivers or big waterholes, or whatever -- these are at headwater locations, rather small streams.There's lots of different species represented -- it's not only elephant or mammoth. There's large masses of bone; there's bone that looks like it could be broken artifactually, or broken to make something out of. And another point that oftentimes is not raised when comparing the modern elephant population depletion during the ivory-hunting craze of 100 years ago is that, in spite of the fact that many elephant populations were driven to about zero -- at least to a virtual zero point -- during the ivory-hunting phase of late 19th century southern Africa, they've recovered to some of the highest densities anywhere in Africa within a hundred years. So elephants can recover from overhunting. How could Clovis people, with spear points, have hunted an entire population of mammoths in North America to extinction, if people with high-powered rifles couldn't do it in the late 19th century?"So, ivory collectors would have just left these culled elephants alone? They just dump the culled bones, don't burn them? How is this similar to what Clovis would use the bones for 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? 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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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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Which part of Jarkov do you mean? The skin I have in my freezer or the bone marrow? Or the disappoitment that it was not a grown version of Dima? Jarkov was badly overhyped. The Pilot site mammoth and the ones that are not reported except to museums are much more interesting not to mention well preserved.

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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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What assertion? I asked you to give an example and you claim it is my assertion..nice evasion there Mr. WilliamsLets see..bovids..no obvious bottlenecksImmunogenetics. 1997;46(3):237-44. Related Articles, LinksAnalysis of genetic diversity at the DQA loci in African cattle: evidence for a BoLA-DQA3 locus.Ballingall KT, Luyai A, McKeever DJ.International Livestock Research Institute (ILRI), Box 30709, Nairobi, Kenya.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. This approach, equally effective in European and Asian cattle breeds, detects the presence or absence of DQA1 and most duplicated DQA2 genes. Nucleotide and predicted amino acid sequence analysis of the highly polymorphic second exons, in addition to analysis of the locus-specific and relatively non-polymorphic transmembrane, cytoplasmic, and 3-prime untranslated regions, has provided evidence for considerable diversity between each of the duplicated DQA2 genes. Therefore, we propose the designation BoLA-DQA3 for the previously unpublished alleles at the second DQA2 locus. Fourteen distinct PCR restriction fragment length polymorphism (RFLP) patterns, each identifying families of alleles at three DQA loci, can be distinguished. Nucleotide sequence analysis of new PCR-RFLP patterns from 193 Kenyan Boran, Ethiopian Arsi (B. indicus), and Guinean N'Dama (B. taurus) cattle identified 13 DQA1 alleles within eight major allelic families, five DQA2 alleles within a single allelic family, and seven DQA3 alleles within three major allelic families.not in horses eitherScience. 2001 Jan 19;291(5503):474-7. Related Articles, LinksComment in:
Science. 2001 Apr 13;292(5515):218-9.
Science. 2001 Jan 19;291(5503):412.Widespread origins of domestic horse lineages.Vila C, Leonard JA, Gotherstrom A, Marklund S, Sandberg K, Liden K, Wayne RK, Ellegren H.Department of Evolutionary Biology, Uppsala University, Norbyvagen 18D, S-75236 Uppsala, Sweden. carles.vila@ebc.uu.seDomestication entails control of wild species and is generally regarded as a complex process confined to a restricted area and culture. 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. Sequence analysis of equids from archaeological sites and late Pleistocene deposits showed that this diversity was not due to an accelerated mutation rate or an ancient domestication event. Consequently, high mtDNA sequence diversity of horses implies an unprecedented and widespread integration of matrilines and an extensive utilization and taming of wild horses. However, genetic variation at nuclear markers is partitioned among horse breeds and may reflect sex-biased dispersal and breeding.moose did have a bottleneck but in eurasia and at the wrong time..Genetika. 2002 Aug;38(8):1125-32. Related Articles, Links[Genetic diversity of moose (Alces alces L.) in Eurasia][Article in Russian]Udina IG, Danilkin AA, Boeskorov GG.N. I. Vavilov Institute of General Genetics, Russian Academy of Sciences, Moscow, 119991 Russia. udi@vigg.ruPolymorphism of nucleotide sequence of D-loop fragment of the mitochondrial DNA was studied in 20 moose from several local populations on the territory of Eurasia. Three main haplotype variants of D-loop were detected by molecular phylogenetic method, which formed three clusters named European, Asian and American. Intraspecies variation in the length of HVSI of D-loop of the mitochondrial DNA of moose was revealed. In the Far Eastern and Yakutian moose, haplotypes with a 75-bp deletion were found, which were most similar with haplotypes (also with the deletion), earlier observed in North American moose [1]. The highest diversity of the haplotypes of mitochondrial DNA is characteristic of Yakutia and the Far East (where three haplotype variants were found), which demonstrates the probable role of the region as the center of the species or as the region of ancient population mixture. The geographic region might be considered as a probable source of ancient moose migrations from Asia to America, basing on the data of distribution of mitochondrial haplotypes of D-loop and alleles of MhcAlal-DRB1. 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. In Europe, only haplotypes of mitochondrial DNA referred to European variant were observed. Basing on analysis of variation of nucleotide sequences of D-loop, exon 4 of kappa-Casein and exon 2 of MhcALal-DRB1, we demonstrated that Eurasian moose studied belong to the unique species, which has probably passed through a bottle neck. The time of the origin of modern diversity of D-loop haplotypes of the species was estimated as 0.075-0.15 Myr ago.canids eitherJ Hered. 1999 Jan-Feb;90(1):71-7. Related Articles, LinksPhylogenetic relationships, evolution, and genetic diversity of the domestic dog.Vila C, Maldonado JE, Wayne RK.Department of Biology, University of California, Los Angeles, USA. Carles.Vila@bmc.uu.seThe 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. Here we review past molecular genetic data that are relevant to understanding the origin and phylogenetic relationships of the dog. DNA-DNA hybridization data show that the dog family Canidae diverged about 50 million years ago from other carnivore families. In contrast, the extant canids are very closely related and diverged from a common ancestor about 10 million years ago. The evidence supporting a close relationship of dogs with gray wolves is overwhelming. However, dogs are remarkably diverse in mitochondrial and nuclear genes. Mitochondrial DNA analysis suggests a more ancient origin of dogs than has been indicated by the fossil record. In addition, dogs have originated from or interbred with wolves throughout their history at different times and different places. We test the possibility of an independent domestication event in North America by analysis of mtDNA variation in the Xoloitzcuintli. This unusual breed is believed to have been kept isolated for thousands of years and may be one of the most ancient breeds in North America. Our results do not support a New World domestication of dogs nor a close association of the Xoloitzcuintli with other hair-less breeds of dogs. Despite their phenotypic uniformity, the Xoloitzcuintli has a surprisingly high level of mtDNA sequence variation. Other breeds are also genetically diverse, suggesting that dog breeds were often founded with a large number of dogs from outbred populations.My muskoxen data is not yet published so I am not putting it here.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? If not, why did the hunters leave such a bounty alone? Your assertion is they were also attacking the other megafauna...can you back it up?

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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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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.

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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:

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Archaeology - Archaeology Magazine

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Now 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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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?Relevant Publications: MacPhee, R.D.E. and P.A. Marx. 1997. The 40,000-year plague: Humans, hyperdisease, and first-contact extinctions. Pp. 169-217. In: Natural Change and Human Impact in Madagascar, S. Goodman and B. Patterson (eds.). Washington, D.C.: Smithsonian Institution Press. MacPhee, R.D.E. and C.E. Flemming. Mammalian extinctions since AD 1500: A preliminary census. In: The Living Planet in Crisis, J.L. Cracraft and F. Grifo (eds.). New York: Columbia University Press, in press.Extinction: Complexity of Assessing Risk
In discussing the extinction risk of nave prey species confronted by reintroduced predators (Science's Compass, 9 Feb., p. 997), J. L. Gittleman and M. E. Gompper say that, apparently because of diverse anthropogenic impacts, "a markedly higher proportion of ungulate species compared with other mammalian taxa have become extinct in the past 500 years."
Not so. Although the belief seems to be widespread that large mammals such as ungulates have suffered substantial losses during the modern era (that is, the last five centuries), the facts lead to a different conclusion. Of the ~90 well-corroborated extinctions that have occurred at the species level within Mammalia during the past 500 years (1), only five species (6%) are members of Ungulata, when the broadest available cladistic definition of this taxon is used (2): two Malagasy hippos (Hippopotamus madagascariensis and H. lemerlei, both extinct around 1500); a North Pacific sirenian (Hydrodamalis gigas, extinct by 1768); and two African bovids (Hippotragus leucophaeus, extinct by 1800, and Gazella rufina, extinct before 1894). Of these, the first three are reasonably regarded as "first contact" extinctions, although the role of human overhunting in forcing these losses is evident only in the case of the sirenian. There is no meaningful evidence regarding the cause of loss of the two African bovids (1).Getting the numbers right is important because extinction (loss of all members of a minimally diagnosable evolutionary unit) is a phenomenon in its own right, although it is often treated as merely the final stage of endangerment. Rating schemes, like the IUCN Red List, that attempt to assign extinction risk factors to endangered species are, of course, extremely important as possible guides to the planet's biotic future. But history is also important, even if its lessons are slippery. For example, the nature and cause of end-Pleistocene extinctions in the continental New World, which Gittleman and Gompper cite for their probative value, are in fact still obscure. If human overhunting of behaviorally nave species were mostly to blame for these losses [amounting to 130 species by our count (1)], how is it that during the past 10,000 years, there have been only two mammalian species-level extinctions (a Mexican cottontail and the sea mink) in the continental Americas--despite significant habitat destruction, numerous exotic introductions, and severe persecution of many species throughout this period. This pattern suggests that we should be looking for other factors as well in first-contact extinctions (3). So who has suffered most among mammals in recent times More than 50% of all species-level losses in the past 500 years are rodents; the groups next most affected are insectivores (13%) and chiropters (bats) (10%). Mammals of large body size (>44 kilograms) account for ~12% of modern-era species losses across all taxa (1). In other words, modern-era mammalian losses have been overwhelmingly minifaunal rather than megafaunal. And they have been overwhelmingly insular: the world's islands have been much more severely affected by species-level extinctions in recent times than have any continental biotopes, including the world's rainforests. If these patterns continue, it is the small, the island-bound, and the least charismatic that will continue to suffer most.So Islands and continents are not different? Why is island biodiversity different then..or is this a Syamsu arugment that there are no real differences among any group, species, etc.?

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Exactly what I have suggested this entire time.

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Where have you been suggesting a mixed approach? 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, you have only defended overkill as the singular cause and then merely handwave in a few references to multicausation at the end of your posts. Where have you supported environmental change having an impact? As I recall you were as dismissive of my refering to climate as you have been to anything else I have said.

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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.

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Because you cannot have such a low population density AND wipe out all the megafauna and leave no trace. And what is the possible use of an untestable unfalsifiable hypothesis? If lack of evidence and presence of absence both support overkill then it is useless scientifically.

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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.

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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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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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Yet you have dismissed every question I ask of you as purely stupid. That is what is insulting. Not that you challenge them. In any case, is there evidence of continental wide environmental impacts in the relevant areas for extinction? Again, evidence for human populations is sparse in this time period. 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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Are you actually trying to claim that this is related to climate change?

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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. This was before humans even left Africa so how could they have been a proximate cause? Mammuthus colombi (not the woolly mammoth) entered North America about 1 million years ago. The extinctions subsequent to this could not have been human initiated. There have been mass extinctions without humans on the scene as Quetzal also pointed out. So what you are addressing is unclear.

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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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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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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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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? Even in Africa? And the arctic they were adapted to is not like Nanook of the North. There is a short growing season where gathering would be possible. And hunting as a sole source of survival in the artic would never have allowed for population explosion.Of course some of the controversial much older dated sites in the Americas for human habitation also screw this scenario up...but also take overill as a cause out as well.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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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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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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What "unusual" migrations were occuring during this period, at a rate fast enough to disrupt long-standing human cultural stances?

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Oh things like this which show very little equilibriumBMC Genet. 2003 Oct 16 [Epub ahead of print]. LinksMitochondrial DNA transit between West Asia and North Africa inferred from U6 phylogeography.Maca-Meyer N, Gonzalez AM, Pestano J, Flores C, Larruga JM, Cabrera VM.Background: World-wide phylogeographic distribution of human complete mitochondrial DNA sequences suggested a West Asian origin for the autochthonous North African lineage U6. We report here a more detailed analysis of this lineage, unraveling successive expansions that affected not only Africa but neighboring regions such as the Near East, the Iberian Peninsula and the Canary Islands.Results: Divergence times, geographic origin and expansions of the U6 mitochondrial DNA clade, have been deduced from the analysis of 14 complete U6 sequences, and 56 different haplotypes, characterized by hypervariable segment sequences and RFLPs. Conclusions: The most probable origin of the proto-U6 lineage was the Near East. Around 30,000 years ago it spread to North Africa where it represents a signature of regional continuity. Subgroup U6a reflects the first African expansion from the Maghrib returning to the east in Paleolithic times. Derivative clade U6a1 signals a posterior movement from East Africa back to the Maghrib and the Near East. This migration coincides with the probable Afroasiatic linguistic expansion. U6b and U6c clades, restricted to West Africa, had more localized expansions. U6b probably reached the Iberian Peninsula during the Capsian diffusion in North Africa. Two autochthonous derivatives of these clades (U6b1 and U6c1) indicate the arrival of North African settlers to the Canarian Archipelago in prehistoric times, most probably due to the Saharan desiccation. The absence of these Canarian lineages nowadays in Africa suggests important demographic movements in the western area of this Continent.Eur J Hum Genet. 2003 Oct 8 [Epub ahead of print]. Related Articles, LinksHuman X-chromosomal lineages in Europe reveal Middle Eastern and Asiatic contacts.Xiao FX, Yotova V, Zietkiewicz E, Lovell A, Gehl D, Bourgeois S, Moreau C, Spanaki C, Plaitakis A, Moisan JP, Labuda D.1Centre de Recherche, Hopital Sainte-Justine, Montreal, Quebec, Canada.Within Europe, classical genetic markers, nuclear autosomal and Y-chromosome DNA polymorphisms display an east-west frequency gradient. This has been taken as evidence for the westward migration of Neolithic farmers from the Middle East. In contrast, most studies of mtDNA variation in Europe and the Middle East have not revealed clinal distributions. Here we report an analysis of dys44 haplotypes, consisting of 35 polymorphisms on an 8 kb segment of the dystrophin gene on Xp21, in a sample of 1203 Eurasian chromosomes. Our results do not show a significant genetic structure in Europe, though when Middle Eastern samples are included a very low but significant genetic structure, rooted in Middle Eastern heterogeneity, is observed. This structure was not correlated to either geography or language, indicating that neither of these factors are a barrier to gene flow within Europe and/or the Middle East. Spatial autocorrelation analysis did not show clinal variation from the Middle East to Europe, though an underlying and ancient east-west cline across the Eurasian continent was detected. Clines provide a strong signal of ancient major population migration(s), and we suggest that the observed cline likely resulted from an ancient, bifurcating migration out of Africa that influenced the colonizing of Europe, Asia and the Americas. Our study reveals that, in addition to settlements from the Near East, Europe has been influenced by other major population movements, such as expansion(s) from Asia, as well as by recent gene flow from within Europe and the Middle East.European Journal of Human Genetics advance online publication, 8 October 2003; doi:10.1038/sj.ejhg.5201097There has never been equilibrium

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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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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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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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What is the negative selection agianst the natives? Co-evolution is not enough as any mutation/behavior that provides an advantage should spread rapidly...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? Why is there no evidence that they did do it? 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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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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As preposterous as hunting a single species to extinction as it become harder and harder to find yet ignoring other species that are abundant and that we know humans have also hunted since the same time period. And not everything that went extinct was in the arctic. The youngest fossils for many of these species do not occur at the highest latitudes. And mammoths and a lot of the extinct megafauna were nowhere near the arctic or not exclusively. Giant ground sloths certainly were not.

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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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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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See the genetic diversity papers...no sign of any bottleneck in the time that all the megafauna is going extinct. Significant hunting would leave an imprint especially given it was not very long ago.

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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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What point would that be? Seriously, a single breeding pair may have all that had been left of the cheetah yet they are not extinct. Elephant seals were decimated, they are stil there...no whales have gone extinct.

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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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Ok so there were not millions of buffalo, elephants in the millions, the population size of mammoths..2 maybe 3? I guess I will have to take your word for this.

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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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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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Except that megafaunal extinctions happened frequently prior to the end Pleistocene and at times where human causes could not have been a factor..so clearly humans are not needed for extinction to occur whether they played a role in this particular extinction or not.

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

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When has there been an equivalent situation to the end Pleistocene regarding immunlogically naive species? There is somne evidence that Xmas Island rats went extinct by introduction of pathogens from ship rats..we are doing the molecular work now...there is also evidence that the thylacine was brought down by disease and not purely by hunting....though some advocates claim it is still alive in the outback.

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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.

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Why would they not be on this scale? Land of plenty..no negative selection...human population only recently became so tremendous...overkill should have been widely supportable yet write up a list of the number of megafauna that went extinct at the end Pleistocene and then do the same for the time since then..what do you think you see?

Thanks Q..but now we are down from 15 to 4 sites.

Hi wmscott,
Thanks for your reply.

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The buffalo survived and exploded, the apparent lack of genetic bottleneck maybe the result of comparison with animals which may have suffered the same crimp in their populations, our yardstick may be bent or sufficient surviving diverse groups prevented the formation of a bottleneck

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.It actually would not have to be in comparison to other animals that had a bottleneck. One would see very little intraindividual genetic diversity in such loci as microsatellites and using a molecular clock the time of the coaslescence of new alleles should be at the end Pleistocene. We don't see this for the relevant species. The only exception are muskoxen which are extremely genetically homogeneous. However, all bovids, equids, cervids, and canids that have been study show tremendous genetic variability that unless one accepts creationist selective group specific mega super hypermutation, should not be present if a gruop or species has suffered a bottleneck.

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On the other hand, perhaps there is just a dating problem that has created the paradox of the Wrangel Island mammoths

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This is very true. Even slightly more extensive dating studies show that we are missing some extremely key datafor example MacPhee et al. 2002. Radiocarbon chronologies and extinction dynamics of the late quaternary mammalian megafauna of the Taimyr Peninsula, Russian Federation. Journal of Archeological Science Vol 29, Issue 2, pp 1017-1042.I would love to find a Taimyr mammoth dating to 4500...then all the extinction hypotheses would be in the toilet

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Like the 20k gap between the disappearance of Neandertal and the end of the Pleistocene, I find it more plausible that considering the scarcity of Neandertal remains that we are just missing some from that time and they were killed off by whatever killed off the animals rather then creating a second mystery on how they disappeared as well. How could they just disappear and take all their genes with them?

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I agree with you. Especially as the fossil remains are so scarce drawing dramatic inferences about what happened to them i.e. we killed them off is premature. Also, there are severe problems with the structure of the genetic studies on neandertals as is it is being peformed i.e. the cro magnon sequence was deemed "unacceptable" by the neandertal crowd because it was "too human". Fine, but then one cannot say anything about neandertal genetics either if any sequence that looks modern is excluded due to contamination fears....then a priori we will only look at and accept the divergent ones which is not an unbiased comparison...anyway, I digress.

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Your very intelligent statement of, "In any case, all three hypotheses are full of holes currently which makes both research and debate rather interesting." is right on the money, my theory has it's holes as well, as you have pointed out, but I believe that with research those holes can be plugged. So far my findings of marine diatoms at an elevation of 1000 ft here in Wisconsin in the center of the North American continent shows that there was a very substantial marine transgression event at the end of the ice age when the extinctions are said to have occurred, it seems highly likely that it had a key role in those extinctions. It will take more very interesting research to measure the extent of the impact of this late ice age marine transgression on the Pleistocene extinctions. I suspect marine flooding will turn out to be the major cause.

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What kind of dates are you finding or at least what is the spread of the dates for a marine transgression? Are there other sites in North America that indicate the same thing as in Wisconsin?Cheers,
M