American Quaternary Extinction Event

[Zirojtan]

So, I was told somebody named Thanas would not be pleased if I didn't know what I was talking about when posting "what ifs" about history. It would be really nice to have someone with which to discuss this stuff though...


So I have a question:


If we are to assume that a combination of Second-Order Predation and Extreme Climate Change was responsible for the American Quaternary Extinction event, then if we remove the first factor, what animals would we be left with, in both North and South America?

[Simon_Jester]

To clarify:

As I understand it, the "second-order predation" hypothesis states that when humans first came to the New World, they were a new predator on the block. Thus, they competed with existing predators for prey, and actively killed some of those predators, causing predator populations to crash. As a result, prey populations started oscillating out of control, the ecosystem is destabilized, and the ensuing boom-bust cycles kill off a lot of herbivore species that couldn't handle the boom-bust conditions well.

So... I assume you're effectively asking, "what species would survive in the Americas had humans not come to those continents in prehistoric times?" Or possibly, "what species would survive in the Americas if the native Americans were all vegetarians," but that would be silly.

We might then ask "what species would climate change be most likely to kill?" And/or "what species would most likely have suffered the most from second-order effects of humans competing with and killing predators?"

[Thanas]

Moved to appropriate forum.

[Thanas]

Also, how hard is it to read the rules?

c) Alternate History
Some alternate history scenarios can serve a purpose and provide for good discussion. When posting an alternate history scenario, make sure that you are able to take part in such a discussion and that your post is not simply a request for information or an argument from ignorance in disguise.

When presenting your Alternate History, your OP should outline a clear argument, including why you are diverting from the official time line and how you think such a change may have affected history, as well as an argument for why such a change might have been possible.

Please take care to actually read the rules in the future. I did not delete your topic as it asked a question about science, but really.

[Zirojtan]

Please take care to actually read the rules in the future. I did not delete your topic as it asked a question about science, but really.

In my experience, the rules of forums are simple, and it's ok to ask questions. I'm sorry if the way in which I asked the question bothered you, but I actually didn't want to go into that level of detail about the PoD of my timeline before I had had an intelligent discussion with people on here in which I might have learned something new that I could use to adjust it before getting poor reviews.

As I understand it, the "second-order predation" hypothesis states that when humans first came to the New World, they were a new predator on the block. Thus, they competed with existing predators for prey, and actively killed some of those predators, causing predator populations to crash. As a result, prey populations started oscillating out of control, the ecosystem is destabilized, and the ensuing boom-bust cycles kill off a lot of herbivore species that couldn't handle the boom-bust conditions well.

In a nutshell, although it is important to note that in the Second-Order Predation Hypothesis, it is not the naïveté of prey animals, but that of predators that is of importance, as predator interaction with one another are learned, where prey animal avoidance of predators is instinctual. Therefore, humans compete with predators who have not learned how to respond to human presence, and predator populations are depleted enough to upset the balance of prey populations, resulting in boom-bust cycles at a fragile time in the ecosystem (the transition from a glacial period to an interglacial).

So... I assume you're effectively asking, "what species would survive in the Americas had humans not come to those continents in prehistoric times?" Or possibly, "what species would survive in the Americas if the native Americans were all vegetarians," but that would be silly.

The PoD for my timeline, which I did not want to share until I had gotten some answeres about which animals people think might have gone extinct by climate change (a question I thought was perfectly clear in the OP), involves Neanderthals reaching the Americas through the development of seal hunting similar to methods employed by the Dorset and Thule cultures of North America OTL. So, that taken into account, as Neanderthals do not seem to have directly caused the extinction of any of the fauna in Europe, their presence might help North American predators learn better how to deal with the presence of humans in a manner similar to that of the Eurasian fauna, thus eliminating the naïveté, and possibly the Second-Order Predation (although I think that it would've still been present, just to a lesser degree).

We might then ask "what species would climate change be most likely to kill?" And/or "what species would most likely have suffered the most from second-order effects of humans competing with and killing predators?"

As we have somewhat of a clear picture of the latter question by which animals are extinct today, the first question is exactly what I was getting at. After we've established what which animals would have been most likely killed by the change in climate, we can then approach which ones might be effected by a less drastic Second-Order Predation model.

[Covenant]

I think that you're going to end up with roughly the same kinds of animals as you ended up with anyway. Like the Cave Bear, it is tempting to think that we killed them off, when it is more likely that a relative (in the case of the Cave Bear, the Brown Bear is the suspect) with a higher degree of flexibility managed to out-compete them as the environment shifted. Humanity in the infancy of the era doesn't have nearly as big of an impact on these populations as climate change. Given how specific predation can be, if a new population replaces an old one... like Moose replacing the Stag-Moose, then you're going to have a shift. You'll even have your bang-bust population yo-yos if a new population of Herbavores suddenly shows up in one already populated.

In any case, despite being a wet blanket, what you're going to want to look at is what creatures humans have a record of introduction with and which did not have direct competition from another animal. Maybe something like the Saiga, which seems very vulnerable to human predation, and would have been a valuable source of meat, fur, and horn. But I have no idea if there's even a tiny fragment of Saiga horn in a human settlement. Not finding one would put a hole in that theory too.

Problem just comes back to there being very little evidence for us having been a deciding factor in most of these megafauna extinctions. Even things you'd think would be prime targets for human attack, like the Giant Beavers, have no record of being hunted by us.

[Zirojtan]

I think that you're going to end up with roughly the same kinds of animals as you ended up with anyway. Like the Cave Bear, it is tempting to think that we killed them off, when it is more likely that a relative (in the case of the Cave Bear, the Brown Bear is the suspect) with a higher degree of flexibility managed to out-compete them as the environment shifted. Humanity in the infancy of the era doesn't have nearly as big of an impact on these populations as climate change. Given how specific predation can be, if a new population replaces an old one... like Moose replacing the Stag-Moose, then you're going to have a shift. You'll even have your bang-bust population yo-yos if a new population of Herbavores suddenly shows up in one already populated.

Ok, climate change hypotheses concerning the severity of the Quaternary Extinction have been picked apart over and over and over again. Primarily because the Pleistocene was a time in which the climate fluctuated in this way multiple times and all of the species that went extinct at the end of this last glacial period survived all of those fluctuations, which in some cases were more severe. Because of this, it does adequately explain the extinction, especially in terms of North America, that is why there is a scientific consensus that the spread of modern humans during the last glacial period across Eurasia and their introduction to North America during this time must have adversely affected the ecosystem in some way. In what way, is a matter of debate, but the Second-Order Predation Hypothesis combined with Extreme Climate Change has so far been the best way to explain it (at least in the Americas) mathematically, as it accounts for both changes in vegetation and in fauna that did not happen in previous interglacials.

In any case, despite being a wet blanket, what you're going to want to look at is what creatures humans have a record of introduction with and which did not have direct competition from another animal. Maybe something like the Saiga, which seems very vulnerable to human predation, and would have been a valuable source of meat, fur, and horn. But I have no idea if there's even a tiny fragment of Saiga horn in a human settlement. Not finding one would put a hole in that theory too.

Problem just comes back to there being very little evidence for us having been a deciding factor in most of these megafauna extinctions. Even things you'd think would be prime targets for human attack, like the Giant Beavers, have no record of being hunted by us.

Honestly, until recently, I did realize just how little archaeological evidence there is for anything at all past say, 6,000 or so years ago. Many of the animals that we tend to think of as having occurred in huge abundance during the Pleistocene have less than 20 actual archaeological sites, and maybe one or two examples of human butchering. So if you're going to look at things in that way, in terms of real bones being discovered with evidence of human butchering, then of course there's very little evidence. But besides the fact that these animals were not affected by previously extreme climate fluctuations, many of those that went extinct, such as horses, should have been prospering, as there was a gradual expansion of their preferred habitats. And then you have the fact that megafauna like Mammoths survived in a few places before humans were introduced into the mix, like Wrangel Island.


Again, the consensus is that climate change doesn't explain the extinction entirely, although it is considered a contributing factor.

[Thanas]

DP by Covenant deleted upon request.

[Zirojtan]

Hmmmm... I guess no other takers on the subject?

[Guardsman Bass]

I'm not sure if I know enough to do a response.

I did read some interesting points about it in The Great Extinctions by Norman Macleod (he's the Keeper of Paleontology at the Natural History Museum, London). He says that the herbivorous mega-fauna that survived in the Americas tended to be characterized by feeding strategies adapted to landscapes with low diversities of plant materials (particularly ruminants such as bison, deer, and moose). The large herbivores that weren't so adapted to that type of forage were much more vulnerable to going extinct during major climate change, and of course that meant the predators who preyed upon them were more vulnerable as well. On top of that, large body size mammals are just in general more likely to go extinct due to smaller population sizes, more specialization on diet, larger geographic ranges required, and fewer average offspring.

Any thoughts? I don't know enough about the subject to either criticize or defend it, but I thought it was worth bringing up. The book, as I mentioned above, is called The Great Extinctions.

[madd0ct0r]

another half formed thought to toss into the ring:

One theory I've come across suggested megafauna comes from herbivores and carnivores are in an arms race - both growing tougher, bigger with more muscle and horns and spikes until both can barely move, go extinct and the cycle starts all over again.

Humans were the disruption factor towards fast and agile in modern species. So perhaps the species that did go extinct, would still go extinct a little later, be replaced by new variants that gradually grow in size until they in turn go extinct.
in short - about now we'd have wolves the size of cows

[Zirojtan]

I did read some interesting points about it in The Great Extinctions by Norman Macleod (he's the Keeper of Paleontology at the Natural History Museum, London). He says that the herbivorous mega-fauna that survived in the Americas tended to be characterized by feeding strategies adapted to landscapes with low diversities of plant materials (particularly ruminants such as bison, deer, and moose). The large herbivores that weren't so adapted to that type of forage were much more vulnerable to going extinct during major climate change, and of course that meant the predators who preyed upon them were more vulnerable as well. On top of that, large body size mammals are just in general more likely to go extinct due to smaller population sizes, more specialization on diet, larger geographic ranges required, and fewer average offspring.

That sounds a bit simplistic to me, and actually sounds like a variation of the Increased Continentality Hypothesis. One of the problems with this hypothesis is that a number of the megaherbivores in questions actually seem to have prospered in continental climates. The North American climate today might be more continental than it was during the Pleistocene, but it isn't actually more continental than Siberia during the Pleistocene, where these megaherbivores (mammoths, woolly rhinoceros, Elasmotherium) were very abundant. Megaherbivores should also have been able to migrate from environments that they found to be too extreme, either seasonally or permanently, and studies have shown that since they stored more fat, their increased body mass should've encouraged adaptations that would compensate for extreme seasonal fluctuations in food availability. This is also taken apart by the fact that various megaherbivores survived on isolated islands until human discovery. Then of course you have the fact that animals that are perfectly well adapted to finding enough food in low-diversity habitats went extinct, i.e. horses. In fact, horses happen to be specialized grazers at this point in their evolutionary history, with your browsing varieties of horses having gone extinct with the expansion of C4 grass habitats in the Miocene and Pliocene. I think about 6 different species of horse disappeared at that point in time. So, if we're to blame over-specialization to a specific kind of habitat, then horses don't fit the bill, since their habitat drastically expanded. Just as well, camelids should also have done well in at least a few areas of North America as habitat generalists, as they did in Eurasia, but all North American species disappear after 10,000 years ago, and a couple South American species as well.

[cosmicalstorm]

I've always found it ridicolous that so many find it so difficult to implicate the rise of h.sapiens with the extinction of the mega-fauna after the last glacial period. Knowing how humans work and what humans value (trophy, easy food, social status) it is extremely obvious that humans did most of the large animals in.

[Ziggy Stardust]

I've always found it ridicolous that so many find it so difficult to implicate the rise of h.sapiens with the extinction of the mega-fauna after the last glacial period. Knowing how humans work and what humans value (trophy, easy food, social status) it is extremely obvious that humans did most of the large animals in.

While it does seem obvious that humans had such an effect (and for the record, I do believe they did, this post is for the sake of playing Devil's advocate), in the name of scientific rigor there's no reason why we have to accept this to be the case. The fact is, the archaeological evidence is not terribly complete in this regard. In fact, there is no direct evidence of heavy human hunting of predatory mega-fauna, and no evidence of a severe decrease in the populations of other predators (brown bears, wolves, mountain lions). Knowing what we know about the behaviors of these predators, we have no reason to think that they would not have filled the niche previously filled by the now extinct predators (cave bears, etc.).

In fact, so far as I can tell through a cursory glance at the available evidence, none of it supports the predictions that you would make through the second-order predation theory.

My point being that there is plenty of room to argue about the mechanisms of the extinction and the role humans may or may not have played in it, and just blandly saying, "Well, we know humans kill stuff, so they must have done it" doesn't really pass any standards of rigor.

[Zirojtan]

Maybe you should take more than just a "cursory glance" at the available evidence, and then compare it to the second-order predation theory. The dissertation, written by Elin Whitney-Smith, is available online, I don't think I can post it here cuz the file's too large.

[Ziggy Stardust]

It is a 220 page dissertation. Perhaps you could cite this paper more specifically, and show me where it presents evidence that contradicts what I said?

So far as I can tell through other sources, the only evidence in favor of second order predation theory is it fits the predictions made by a computer model, rather than anything specific in the archaeological record. Not that this makes it "wrong," in fact (and not that I actually have an opinion with relation to this specific hypothesis), but rather that the question still seems to be pretty open to discussion/debate.

(Also, as a side note, is there another name for second order predation theory? When I search it on Google scholar, virtually no results come up except for papers by Elin Whitney-Smith. This is typically a major red flag in the hard sciences, as it tends to indicate that it is not even discussed in the literature. In fact, the few recent papers I can find that cite the theory don't even discuss it in any specificity, merely listing it along with several dozen other extinction models, usually followed by a comment along the lines of, "This strongly suggests to some investigators that a more interesting extinction debate lies within the realm of potential human-caused explanations and how climate might exacerbate human impacts. New obser- vations emerging from refined dating techniques, paleoecology and modeling suggest that the mega- faunal collapses of the Americas and Australia, as well as most prehistoric island biotic losses, trace to a variety of human impacts, including rapid overharvesting, bio- logical invasions, habitat transformation and disease." Look here, for instance. If you are convinced as to the veracity of this particular hypothesis, perhaps you can point me to some more firm evidence?)

[Alyrium Denryle]

I am so glad I found this thread

In a nutshell, although it is important to note that in the Second-Order Predation Hypothesis, it is not the naïveté of prey animals, but that of predators that is of importance, as predator interaction with one another are learned, where prey animal avoidance of predators is instinctual.

Wrong on both counts, because depending on the organism, it is a combination of both learning and innate behaviors for both predator and prey.

So, that taken into account, as Neanderthals do not seem to have directly caused the extinction of any of the fauna in Europe, their presence might help North American predators learn better how to deal with the presence of humans in a manner similar to that of the Eurasian fauna, thus eliminating the naïveté, and possibly the Second-Order Predation (although I think that it would've still been present, just to a lesser degree).

No. H. neanderthalensis were obligate carnivores (or mostly so), the only reason they may not (and I will need to look that up) have decimated european populations of animals was because the climate was harsh and their own populations pretty bloody small (it is really hard to live at high density as a relatively large carnivore on what is essentially Taiga and alpine tundra). They were outcompeted by H. sapiens because the later was a lot more flexible and had stronger social adaptations. Imagination sufficient to produce artwork and invent new tools at a prodigious rate is no small thing.

H. sapiens reaches high density because when prey is scarce, they can live on other foodstuffs, decoupling their populations from prey populations, while still heavily depredating the local wildlife.

That said, the organisms that coexisted within the native range of H. neanderthalensis co-evolved with them, starting with H. heidelbergensis, for 200k years before H. neanderthalensis can be found in the fossil record. If the secondary predation hypothesis is true, the native fauna of the Americas would be just as screwed, provided Neanderthals could survive the climate change if-not-for-H. sapiens-competition. That is a bit of a maybe.


---

Now for the proverbial meat.

If we assume that humans never show up... the actual cause of extinction in the Quaternary is probably a combination of the indirect effects of climate change, direct thermal stress, and human predation pressure. Larger species with more insulation are more vulnerable to this. When temperature goes up by 6 degrees celsius over a short time interval... large organisms with a low surface area/volume ratio will suffer direct thermal stress and as a result will be subject to range contractions. Thick fur coats prevent heat exchange. Animals with specialized diet or habitat requirements will also suffer under these conditions. The most likely candidates for definite extinction are species for which both of these conditions apply, with the remainder for which only one condition applies being... difficult to distinguish from random using the fossil record. It is often a matter of luck when it comes to surviving a selective filter like that. "Does a species occupy an area that is suitable habitat in both climatic conditions" being the operative question, and if there are geographic barriers, the answer may well be No. Or, if yes, then their distribution is patchy with limited gene flow, and if one population goes under, the other may be reduced in size and go extinct due to inbreeding depression.

Now, if you combine people into the mix, yeah. They are likely to have either killed directly, or indirectly through competition and Trophic Cascades, some of the species that would otherwise have made it through the selective filter.

When I search it on Google scholar, virtually no results come up except for papers by Elin Whitney-Smith. This is typically a major red flag in the hard sciences, as it tends to indicate that it is not even discussed in the literature. In fact, the few recent papers I can find that cite the theory don't even discuss it in any specificity, merely listing it along with several dozen other extinction models

That is not... actually unusual. "secondary predation", otherwise known as a "trophic cascade". The problem is, paleontologists are not actually ecologists, and trophic cascades are fresh enough in terms of how well we understand them that paleontologists might not incorporate them into their models for a while.

[Ziggy Stardust]

That is not... actually unusual. "secondary predation", otherwise known as a "trophic cascade". The problem is, paleontologists are not actually ecologists, and trophic cascades are fresh enough in terms of how well we understand them that paleontologists might not incorporate them into their models for a while.

I don't know how things work in paleontology in general, but in my personal experience (in psychology, cognitive neuroscience, and neuroethology; which I admit are radically different fields) it is pretty unusual for a 13 year old model to not even be widely cited or mentioned in the literature if it is at all taken seriously. I will concede that I don't know how different things may be for paleontology, but you would expect it to show up, at the very least, in review papers or paper backgrounds if it is widely accepted.

But "second order predation" comes up with 25 hits on Google scholar - and many are by the same author. (Remember, I am referring rather specifically to this specific hypothesis with reference to the Quaternary extinction event, not the premise of secondary predation/trophic cascades in general. The "second order predation" hypothesis discussed in this thread is not synonymous with trophic cascade as a general concept, though they are related). Even if you look at the relative citation patterns of the other Quaternary extinction hypotheses, they all come up with significantly more hits in the literature.

I understand this is not my field, but this is a red flag at least with regards to how seriously this hypothesis is considered with respect to the others. Further, when reading the papers that are associated with it, there doesn't appear to be any actual physical evidence presented in favor of it, and it seems to have been proposed entirely on the basis of it fitting a computer model.

EDIT: For the record, I am not arguing against the idea that humans played a role in the Quaternary extinction. I think it is obvious that they did, in combination with other factors as you discussed. I am merely playing Devil's advocate against the OP's apparent zeal for this specific model.

[cosmicalstorm]

I have heard one argument stating to the effect that the mega-fauna survived 23 glacial periods before the current extinctions. It seems even the large animals can adapt rapidly enough to survive the various climate changes that occur when a glacial period ends. This last glacial ending could not have been so very different than the other ones could it? And this is consistent with what I know of natural selection and genetics and some recent epi-genetics, namely that animals animals have the capacity to evolve extremely fast during heavy selection pressure. I have heard of animals on islands who can undergo rapid size change in under few generations, almost as if their bodies were able to effect some kind of epi-genetic reprogramming as an answer to environmental change. With this in mind it seems strange that everything disappeard on the 24'th round, when this murderous hairless ape with a glowing mind showed up everywhere at once. It seems rather obvious that humans played a large part in the extinction. However, I am not providing good sources here, and I write this out of memory so please take it with a grain of salt, and please correct me if I'm wrong.

[Guardsman Bass]

I have heard one argument stating to the effect that the mega-fauna survived 23 glacial periods before the current extinctions. It seems even the large animals can adapt rapidly enough to survive the various climate changes that occur when a glacial period ends. This last glacial ending could not have been so very different than the other ones could it? And this is consistent with what I know of natural selection and genetics and some recent epi-genetics, namely that animals animals have the capacity to evolve extremely fast during heavy selection pressure. I have heard of animals on islands who can undergo rapid size change in under few generations, almost as if their bodies were able to effect some kind of epi-genetic reprogramming as an answer to environmental change. With this in mind it seems strange that everything disappeard on the 24'th round, when this murderous hairless ape with a glowing mind showed up everywhere at once. It seems rather obvious that humans played a large part in the extinction. However, I am not providing good sources here, and I write this out of memory so please take it with a grain of salt, and please correct me if I'm wrong.

But then the question becomes "why did some mega-fauna die out, and not others?". Why did mammoths die out, and not buffalo/bison, for example? Or horses/camels, but not llamas and pronghorn?

[Zirojtan]

It is a 220 page dissertation. Perhaps you could cite this paper more specifically, and show me where it presents evidence that contradicts what I said?

I believe 272 pages, and if I can read through it all in a day, then I can anyone else can if they have the time and the patience.


However, while there are good arguments in the dissertation, one only need to look to how predatory guilds and niche partitioning works to refute what you said. You said, essentially: "Why couldn't the surviving predators adapt to fill the niches of the extinct or decimated ones, if we take the Second-Order Predation Hypothesis into account?" Because that's not how the ecosystem was set up, and many of the surviving predators are not specifically adapted for the prey animals of the period. Bison were considerably larger, so were a few of the species of horse, as well as the species of camel, Camelops, and mammoths and sloths. Arctodus simus and Tremarctos floridanus are called "running bears" because of their adaptations to hunt very LARGE prey animals in open environments. Grizzly bears and black bears of today don't even compete, and they're also pretty omnivorous, subsisting more on plants than they do on meat, so the megafaunal extinction was not an issue for them in the same way. Likewise, cougars, while magnificent, are a much smaller kind of cat than Smilodon, Panthera leo atrox, or even Homotherium, which was quite slenderly built. The North American ecosystem was partitioned in a very specific manner, and it seems that the exhaustion of the ecosystem proposed in the hypothesis did not adversely effect the surviving predators in the same way, as their prey didn't seem to suffer, so there would be no incentive beyond the fact that a niche was open. That being said, while that is kind of how animals evolve to take up new ecological niches, that's a very long process that takes a little longer than a couple of thousand years, which is what we're being presented with here.

So far as I can tell through other sources, the only evidence in favor of second order predation theory is it fits the predictions made by a computer model, rather than anything specific in the archaeological record. Not that this makes it "wrong," in fact (and not that I actually have an opinion with relation to this specific hypothesis), but rather that the question still seems to be pretty open to discussion/debate.

Of course it's open to debate. It's not scripture... But I didn't post this topic to debate the hypothesis. In my original post, I said: "Assuming the Second-Order Predation Hypothesis is true...", or something to that effect. I personally think that it best explains the extinctions, and there's a variety of evidence within it besides a computer model, such as detailed descriptions of what is found in the archaeological record as well as recorded and widely excepted patterns of change in vegetation from the Pleistocene-Holocene, examples of predator-prey relationships today as well as a fine example of how a large proboscidean can destroy its environment using observed data from African elephants. However, that doesn't mean that I think that it's gospel. I think that the example used to show predator naivety (reintroduced wolves and red foxes) was a very big generalization to make. I'm sure that Ms. Whitney-Smith has more examples in her book, and when I buy it, I'll let you know. But I chose to adhere to this hypothesis for the sake of my timeline solely because it means that I don't have to radically alter human behavior in a very unrealistic manner, and can instead attempt to explain an alternate extinction pattern that will leave some more domesticable animals with the introduction of hominins into the mix, lending the animals in the ecosystem 106,000 years to get used to their presence.


Personally, I think I'm doing a pretty damned good job considering that everybody else who attempts to write about the idea of certain animals surviving the Quaternary Extinction Event usually just says: "For whatever reason..." or "For reasons lost to history..." The Second-Order Predation theory might not be completely or even remotely accurate, future discoveries in science will tell, but for now, it is a decent explanation, and the best explanation for fitting the purposes of the timeline. That's the extent of my "zeal" for the subject.

Wrong on both counts, because depending on the organism, it is a combination of both learning and innate behaviors for both predator and prey.

... When you use a generalistic term like "organism", then I suppose so. But when you compare it to the closest modern-day analogues, this seems to be the case, at least according to what I've read. I'm not sure if there are very many examples of previously extirpated predators being reintroduced to a specific geographic region to compete with predators they once shared that environment with that are well-studied enough to draw from.

No. H. neanderthalensis were obligate carnivores (or mostly so), the only reason they may not (and I will need to look that up) have decimated european populations of animals was because the climate was harsh and their own populations pretty bloody small (it is really hard to live at high density as a relatively large carnivore on what is essentially Taiga and alpine tundra). They were outcompeted by H. sapiens because the later was a lot more flexible and had stronger social adaptations. Imagination sufficient to produce artwork and invent new tools at a prodigious rate is no small thing.

Ok, THAT, is sooooooo not proven. That is a very hotly debated subject in paleontology, archaeology and anthropology and has very little evidence besides a perceived lack of Neanderthal artistic expression, and some recent studies that say that the structuring of their brains may have resulted in what you just said. The only thing that was in that paragraph that can honestly be said to have some really good evidence behind it is the statement that they were probably obligate carnivores, which is backed up by numerous Neanderthal turds that have been studied that showed that they could digest meat at the same or similar level of efficiency to wolves. What you said about their population however actually most probably owes itself more to their habitat specialization than it does to anything else, as they are now thought to have been hypercarnivorous ambush predators of woodlands, with a special emphasis on wooded highlands. That being said, their preferred habitat was not very big except during interglacials, but once glacial periods began, with the extensive continentality of Europe and Asia, they would've been restricted to a few pockets where their habitat persisted.


North America had extensive boreal forests on the East Coast, much larger then what was available to them in Europe, and with an abundance of slow-moving, large prey animals (Castoroides, Paramylodon, Eremotherium, and a woodland proboscidean in mastodons), I can actually see them doing quite well. Mind you, the Neanderthals in the timeline have already adopted in many areas a new subsistence strategy, and so will not be as limited as they were OTL, but that doesn't mean that I'm trying to argue for their survival in North America in this timeline. They will go extinct here with the introduction of poxviruses by modern humans.

That said, the organisms that coexisted within the native range of H. neanderthalensis co-evolved with them, starting with H. heidelbergensis, for 200k years before H. neanderthalensis can be found in the fossil record. If the secondary predation hypothesis is true, the native fauna of the Americas would be just as screwed, provided Neanderthals could survive the climate change if-not-for-H. sapiens-competition. That is a bit of a maybe.

I think 106,000 years is a decent amount of time to make some room in the predator guild if we use the Second-Order Predation Hypothesis, don't you?

If we assume that humans never show up... the actual cause of extinction in the Quaternary is probably a combination of the indirect effects of climate change, direct thermal stress, and human predation pressure. Larger species with more insulation are more vulnerable to this. When temperature goes up by 6 degrees celsius over a short time interval... large organisms with a low surface area/volume ratio will suffer direct thermal stress and as a result will be subject to range contractions. Thick fur coats prevent heat exchange. Animals with specialized diet or habitat requirements will also suffer under these conditions. The most likely candidates for definite extinction are species for which both of these conditions apply, with the remainder for which only one condition applies being... difficult to distinguish from random using the fossil record. It is often a matter of luck when it comes to surviving a selective filter like that. "Does a species occupy an area that is suitable habitat in both climatic conditions" being the operative question, and if there are geographic barriers, the answer may well be No. Or, if yes, then their distribution is patchy with limited gene flow, and if one population goes under, the other may be reduced in size and go extinct due to inbreeding depression.

Yes...


Temperature really can't be said to have played a factor, since the very same animals seem to have been unaffected by the previous... 23 was it? 23 interglacial periods, the one immediately proceeding the Weichselian Glaciation (the last ice age) having actually completely melted the ice caps, and exposed large sections of Greenland. Taking that into account, and also the ease at which arctic animals seem to be able to handle the temperatures at zoos in more temperate areas, which they normally do by decreasing their fat reserves, as hair is not the only factor in keeping an animal warm.

Animals with specialized diet or habitat requirements will also suffer under these conditions

Indeed, and this was where I was going with the original post before somebody tried to argue that it was mostly climate change, thereby hijacking the entire discussion from trying to find out which animals suffer the most from climate change if we remove the human factor in a Second-Order Predation model to a debate about the model's actual validity.

I don't know how things work in paleontology in general, but in my personal experience (in psychology, cognitive neuroscience, and neuroethology; which I admit are radically different fields) it is pretty unusual for a 13 year old model to not even be widely cited or mentioned in the literature if it is at all taken seriously. I will concede that I don't know how different things may be for paleontology, but you would expect it to show up, at the very least, in review papers or paper backgrounds if it is widely accepted.

I'm not sure either, since I'm not a paleontologist, but what I can say is that the most recent papers on the issue don't really present anything new. I've read quite a few "different" approaches to the subject over that past few months, and this one is actually the one I can find that isn't easily visible as a slight variation of another one, and it also doesn't stick its foot in its mouth with unfounded or outdated assumptions about the animals in question (such as a 2 year old trophic cascade model that I read the other day that claimed that Homotherium was a specialist in killing mammoths and other megafauna, even though this is no longer believed to be the case). Maybe it's something like linguistics, which in my experience, having gone to school for it, is very much a good ol' boys club with its own cliques. I've spoken with the author of the dissertation, Ms. Whitney-Smith, and to be honest, she's not very pleasant, and though she does seem to be very intelligent, given her writing anyways...

[Ziggy Stardust]

That being said, while that is kind of how animals evolve to take up new ecological niches, that's a very long process that takes a little longer than a couple of thousand years, which is what we're being presented with here.

Why would this process be necessarily slower than the proposed boom/bust cycles? Especially given that we are not talking about the evolution of new behaviors or adaptations. Further, we know from more recent and documented examples that predators like wolves, coyotes (Pleistocene coyotes were also quite large compared to the modern ones, as a matter of fact), and cougars are far more plastic in their behaviors than you seem to give them credit for. Modern populations of these species have changed their behaviors and ranges with respect to shifts in human habitation/hunting over a much shorter time frame. (Also, for the record, the adult size of the prey species doesn't mean that much, as predators tend to go for the sick/injured/young/old over healthy adults of larger prey.)

I personally think that it best explains the extinctions, and there's a variety of evidence within it besides a computer model, such as detailed descriptions of what is found in the archaeological record as well as recorded and widely excepted patterns of change in vegetation from the Pleistocene-Holocene, examples of predator-prey relationships today as well as a fine example of how a large proboscidean can destroy its environment using observed data from African elephants.

Where is this evidence? I So far as I can tell through a search on Google scholar, there is no archaeological evidence, and it is not "widely excepted" [sic]. As I already noted, the paper is barely even cited by other papers in the field.

Looking through the thesis paper, almost the entire thing is devoted to the parameters of the model. Which is fine, there is nothing inherently wrong with this. But I cannot find a detailed discussion of the evidence. And as the author of the paper notes on page 196,

The first challenge for further research would be to find field evidence to support or falsify the theory.

So, I ask you, where is the evidence to which you keep referring? I am not trying to sound combatative about this, I am honestly just curious. I apologize if this has come off as more of an attack than an inquiry, but that was not how I intended it. It is just from my attempts to look at the issue, through what information is available online, I cannot find a justification for accepting it.

[Zirojtan]

I really do hate losing a long post half way through...


Damn you dad, for asking me to come out and help you get rid of those stumps, and damn you laptop for being such a piece of poop.


Anyways, what you're about to get is a greatly condensed version of what I previously wrote, as I don't have the patience to write it twice in one evening.

Further, we know from more recent and documented examples that predators like wolves, coyotes (Pleistocene coyotes were also quite large compared to the modern ones, as a matter of fact), and cougars are far more plastic in their behaviors than you seem to give them credit for

Yes, but they were not large enough to efficiently hunt the megafauna. Take gray wolves for example, and their interaction with bison. A National Geographic Documentary that I watched the other day on Youtube about dire wolves included footage from a 36 hour engagement of modern gray wolves with a bison in which the biologists narrating explained that modern gray wolves have trouble taking down such large prey as opposed to smaller (yet, still large, comparatively speaking) prey such as elk. I was interested in the subject and found a short PDF entitled Megafaunal Extinctions and the Disappearance of a Specialized Wolf Ecomorph that is available for free on Google. In the document, it is described how modern gray wolf haplotypes have little in common with a number of gray wolf haplotypes from the Pleistocene, suggesting that they do not share a common ancestor, and that the modern population's low genetic diversity suggests a significant reduction in population and spread from a small, surviving population. It also goes into talking about how a significantly larger morph of the gray wolf was present in Beringia that seems to have filled the ecological niche held by dire wolves south of the ice sheets as hunters of large prey including horses, bison, musk ox, and a mammoth here and there.


So to summarize, it seems that gray wolves were effected by the Quaternary Extinction Event, and that they have and are continuing to alter their behaviors to fill niches left to them by a decimated predator guild. There are also similar studies concerning modern day North American cougars, who also exhibit a surprisingly low genetic diversity.


Now, how does this pertain to the Second-Order Predation model? Well, obviously there was a significant reduction in predator populations that you might not expect if the cycle goes the other way, with the extinction of large herbivores leaving large carnivores without the prey that they need to sustain themselves. Of course, maybe there was also a reduction in the populations of smaller prey animals that cougars and gray wolves relied on, but I've never read anything that suggests that. In fact, everything I've ever read on this suggests the contrary, as the extinction visibly seems to have favored these smaller herbivores.

Where is this evidence? I So far as I can tell through a search on Google scholar, there is no archaeological evidence, and it is not "widely excepted" [sic]. As I already noted, the paper is barely even cited by other papers in the field.

Ok, this is where I was when I had to go pull stumps...


Now I have to ask, how much of the dissertation did you read? Did you just skim through it? Because I don't know how you would've missed this stuff if you had read it all, or at least that much of it which isn't mathematics and computer modeling. This will take a bit, but I have a bit now, so that's ok:


At the end of page 41, she cites a paper written by Hawkes and O'Connell in 1994 in which their studies of modern day hunter gatherers suggest that pre-agricultural humans (bolded, underlined, and italicized, because we know this definitely isn't true of agricultural societies) as economically thinking omnivores, are actually less likely to over-hunt their prey than non-human predators because of the observed ease with which they switch prey animals in times of scarcity, because utilization is actually based on frequency of encounter and profitability of encounter, and as that frequency decreases, other food sources are more likely to be utilized. It's easier for us anyways, because we're far more omnivorous than pretty much every large predator with which we've competed. It's not concrete evidence, but I think it lends a little weight to it.


On page 47 she cites Janis in 1975 and Guthrie in 1989 for the extinction's bias towards significantly smaller ruminants, which of course is blatantly obvious, as today we have deer, pronghorns, bison, sheep, goats, caribou, elk, and moose, and we lack horses, sloths, glyptodonts, pampatheres, mammoths, mastodons, camels, and llamas (although there are some ruminants that disappear, like Micromeryx, Stockoceros, Euceratherium, and Bootherium). Her reasoning is that the bias in favor of ruminants, who are better at extracting nutrients from their food, therefore needing much less of it, over monogastrics, suggests a scarcity in food.


On page 51, as we get into the "Argument for Second-Order Predation" section, she sites an interesting study in 1988 (Leader-Williams et al.) where the lack of natural predators of caribou on Antarctic Islands on which they were introduced led to a population bust via exhaustion of the environment. Now she doesn't cite anything about the White Tailed Deer problem back East, but I've seen a couple documentaries on this, one in which a biologist fenced off a certain section of the forest for about 10 years, allowing new shoots that the deer were eating to grow that increased the density and brought back a number of snake, bird, lizard, and insect species that were becoming scarce.



At the end of page 52, she talks about the introduction of rinderpest to Africa, and how the reduced population of traditional prey of the lions caused a change in the mutual avoidance relationship that had been established with humans, causing them to prey on humans, which in turn caused an anti-lion pogrom, which allowed the populations of wildebeest and buffalo to grow, although not reaching the same numbers as they did in pre-rinderpest times; probably due to the continued presence of the disease. Now, you could easily flip that and say that the newly arrived humans upsets the established partition of prey in the predator guild, causing certain prey animal populations to crash so much that predators begin to actively prey on humans, and then you get an anti-predator pogrom that reduces the population of the predator, causing the prey population to bounce back (slowly), and exceed its normal limit. Although you could also achieve this kind of predatory hostility towards humans without their hunting of a certain predator's prey, since their presence already upsets the prey partitioning, and so puts them in direct competition anyways.


Page 53 is where she talks about the relationship of mutual avoidance that was previously established between wolves, foxes, and coyotes in many parts of North America prior to the extirpation of wolves, which led coyotes and foxes to unlearn that behavior after a certain amount of time before wolves were reintroduced, whereas elk didn't unlearn their protective behaviors, and were prepared for the wolves' reintroduction. The reintroduced wolves can frequently be observed killing coyotes and foxes to eliminate competition in areas that they have been reintroduced. Now, she doesn't cite this, because I don't think that studies had been done on it at the time, but you see the same thing with the introduction of raccoon dogs in areas of Europe where wolves remain extant (Italy, Eastern Europe), where wolves have been observed to kill them rather indiscriminately and not eat their carcasses.


And finally, because I'm tired, page 55 is where she cites about 10 or so different studies that observed the destruction of habitats by African herbivores in the absence of predators, most famously the ability of elephants to turn mixed woodlands into grasslands by engaging in their normal behavior of knocking over trees to get at leaves which can obviously damage the environment if the population is not kept down. She cites Wing and Buss in 1970 that elephants, combined with natural fires have been observed transforming landscapes this way in as little as 50 years.

So, I ask you, where is the evidence to which you keep referring? I am not trying to sound combatative about this, I am honestly just curious. I apologize if this has come off as more of an attack than an inquiry, but that was not how I intended it. It is just from my attempts to look at the issue, through what information is available online, I cannot find a justification for accepting it.

Well, there's some of it. And thank you for clarifying, cuz you kind of did come across that way


I'm not sure why her paper is not cited very often, but what I do know is that the Quaternary Extinction Event is the Olympics of paleontological debate. Everything else that I have read on this matter only explains part of the story, as everyone else is proposing either overkill, climate change, or hyperdisease, and many of them also don't seem to be consistent with research about the animals in question. For example, the trophic cascade model that I read a week or so ago that claimed empirically that Homotherium was definitely a predator of megaherbivores, like mammoths, even though some of the most renowned experts in the field of Pleistocene Carnivores, like Mauricio Antón, don't think that this was the case. Or, other models that suggest that climate change empirically accounts for the disappearance of animals like the "giant beaver" Castoroides (which actually doesn't seem to have had a lot in common with beavers besides being in the same family), even though their optimal habitats increased after the Pleistocene-Holocene transition.


So yeah, I really don't know. But to me at least, it seems to fit with most of what I've read, and that's why I've picked it as the model for my timeline. However I'm not basing everything solely off of this PDF. There is evidence that disease may have played some role at least in the disappearance of mastodons, who appear to have been suffering from an outbreak of tuberculosis towards the end (introduced by humans), which is why I have placed the arrival of humans in the Americas in the timeline before the hypothesized evolution of TB. Also, the model doesn't really take into account the damaging effect that hunting sexually dominant male elephants can have in destabilizing the social hierarchy, and the effects that that can have on populations of both elephants and other animals (sexually frustrated younger males in musth whose behavior is not regulated by dominant males were observed to be killing rhinoceros en masse in Africa after rhinoceroses had turned down their sexual advances). If mastodons and mammoths behaved anything like extant proboscideans, which it is hypothesized that they did, then this is definitely something to take into consideration as well. We haven't found any evidence of mammoths/mastodons killing animals that turned down their sexual advances in the same way that elephants killed rhinos (perhaps sloths, or bison, maybe even camels?), but there's extensive evidence that mastodons at least were getting very aggressive with each other towards the end.


EDIT: Just so you know, I ALMOST lost this post too... I was ready to just say fuck it and give you my Facebook so we could chat.

[cosmicalstorm]

Humans to blame for extinction after Ice age:

The late Quaternary megafauna extinction was a severe global-scale event. Two factors, climate change and modern humans, have received broad support as the primary drivers, but their absolute and relative importance remains controversial. To date, focus has been on the extinction chronology of individual or small groups of species, specific geographical regions or macroscale studies at very coarse geographical and taxonomic resolution, limiting the possibility of adequately testing the proposed hypotheses. We present, to our knowledge, the first global analysis of this extinction based on comprehensive country-level data on the geographical distribution of all large mammal species (more than or equal to 10 kg) that have gone globally or continentally extinct between the beginning of the Last Interglacial at 132 000 years BP and the late Holocene 1000 years BP, testing the relative roles played by glacial–interglacial climate change and humans. We show that the severity of extinction is strongly tied to hominin palaeobiogeography, with at most a weak, Eurasia-specific link to climate change. This first species-level macroscale analysis at relatively high geographical resolution provides strong support for modern humans as the primary driver of the worldwide megafauna losses during the late Quaternary.

http://rspb.royalsocietypublishing.org/ ... 7/20133254

[madd0ct0r]

seems this thread dosen't go extinct though