# What caused the Pleistocene/Holocene extinction? Human hunters, or climate change? **URL:** \ **Category:** Great Debates\ **Created:** [April 20, 2006, 12:32am UTC](https://boards.straightdope.com/t/what-caused-the-pleistocene-holocene-extinction-human-hunters-or-climate-change/353398 "2006-04-20T00:32:00Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![BrainGlutton](https://avatars.discourse-cdn.com/v4/letter/b/82dd89/32.png) [@BrainGlutton](https://boards.straightdope.com/u/BrainGlutton)\ **Post date:** [April 20, 2006, 12:32am UTC](https://boards.straightdope.com/t/what-caused-the-pleistocene-holocene-extinction-human-hunters-or-climate-change/353398/1 "2006-04-20T00:32:00Z")
Between 13,000 and 9,000 years ago, a great many “megafauna” – large mammals – went extinct all over the world. This was the sixth known “mass extinction event” in the planet’s history. There are two main theories as to what caused it: 1. Humans spread out from Africa and hunted the megafauna to extinction, either directly, or by interrupting their food supply. 2. They died out from natural climate change (the end of the last Ice Age), to which they could not adapt fast enough. [http://en.wikipedia.org/wiki/Holocene\_extinction\_event](http://en.wikipedia.org/wiki/Holocene_extinction_event) Which is it? Note: There was no significant extinction in Africa – where large mammals had a change to evolve alongside humans and gradually adapt to their presence, and which still supports more large mammals than any other continent. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [April 20, 2006, 4:54am UTC](https://boards.straightdope.com/t/what-caused-the-pleistocene-holocene-extinction-human-hunters-or-climate-change/353398/2 "2006-04-20T04:54:19Z")
> [@BrainGlutton](#): > > Which is it? It’s not an either/or question. A recent review by Anthony Barnosky et al. concludes that it was the combination of human pressure and climate change that produced the extinction, with climate being more important in some areas and humans in others. [Climate Change Plus Human Pressure Caused Large Mammal Extinctions In Late Pleistocene](http://www.sciencedaily.com/releases/2004/10/041001092938.htm) [Here’s](http://sciencereview.berkeley.edu/articles/issue9/large-mammal.pdf) a pdf of another article. The article itself is: Barnosky, Anthony D., Paul L. Koch, Robert S. Feranec, Scott L. Wing, Alan B. Shabel. 2004. Assessing the Causes of Late Pleistocene Extinctions on the Continents. _Science_ 306: 70-75. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [April 20, 2006, 4:57am UTC](https://boards.straightdope.com/t/what-caused-the-pleistocene-holocene-extinction-human-hunters-or-climate-change/353398/3 "2006-04-20T04:57:47Z")
Here’s the abstract of Barnosky et al.: > [@](#): > > One of the great debates about extinction is whether humans or climatic change caused the demise of the Pleistocene megafauna. Evidence from paleontology, climatology, archaeology, and ecology now supports the idea that humans contributed to extinction on some continents, but human hunting was not solely responsible for the pattern of extinction everywhere. Instead, evidence suggests that the intersection of human impacts with pronounced climatic change drove the precise timing and geography of extinction in the Northern Hemisphere. The story from the Southern Hemisphere is still unfolding. New evidence from Australia supports the view that humans helped cause extinctions there, but the correlation with climate is weak or contested. Firmer chronologies, more realistic ecological models, and regional paleoecological insights still are needed to understand details of the worldwide extinction pattern and the population dynamics of the species involved. ---
**Author:** ![John\_Mace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_mace/32/185_2.png) [@John\_Mace](https://boards.straightdope.com/u/John_Mace)\ **Post date:** [April 20, 2006, 5:33am UTC](https://boards.straightdope.com/t/what-caused-the-pleistocene-holocene-extinction-human-hunters-or-climate-change/353398/4 "2006-04-20T05:33:11Z")
Of course \*\*Colibri \*\*nailed it. This is a subject about which biologists are doing research and publishing papers. I’m not sure I see the point of a bunch of amateurs debating a subject such as this. Although there isn’t strictly a factual answer to the OPs question, this thread would probably be more suited to GQ. ---
**Author:** ![Frank](https://avatars.discourse-cdn.com/v4/letter/f/3d9bf3/32.png) [@Frank](https://boards.straightdope.com/u/Frank)\ **Post date:** [April 20, 2006, 5:42am UTC](https://boards.straightdope.com/t/what-caused-the-pleistocene-holocene-extinction-human-hunters-or-climate-change/353398/5 "2006-04-20T05:42:02Z")
> [@John Mace](#): > > Of course \*\*Colibri \*\*nailed it. This is a subject about which biologists are doing research and publishing papers. I’m not sure I see the point of a bunch of amateurs debating a subject such as this. Although there isn’t strictly a factual answer to the OPs question, this thread would probably be more suited to GQ. I’d say that the wikipedia article was written by an amateur, or by a pro doing an extremely poor job of talking down. It is, however, a very interesting question to many of us amateurs, and I’ll be fascinated to follow the argument when those who actually do know what they are talking about pick up this thread. Even if it’s just to say, “Umm, dunno.” ---
**Author:** ![Apos](https://avatars.discourse-cdn.com/v4/letter/a/838e76/32.png) [@Apos](https://boards.straightdope.com/u/Apos)\ **Post date:** [April 20, 2006, 5:52am UTC](https://boards.straightdope.com/t/what-caused-the-pleistocene-holocene-extinction-human-hunters-or-climate-change/353398/6 "2006-04-20T05:52:20Z")
> [@John Mace](#): > > Of course \*\*Colibri \*\*nailed it. This is a subject about which biologists are doing research and publishing papers. I’m not sure I see the point of a bunch of amateurs debating a subject such as this. Although there isn’t strictly a factual answer to the OPs question, this thread would probably be more suited to GQ. 50 QUATALOOS ON THE CLIMATE CHANGE! (i.e., I agree. There’s no solid answer, and people who don’t spend their time pouring over statiscal breakdowns of climate data, paleoecology journals, and so on aren’t going to have much to add, or even good groudns to debate a side) ---
**Author:** ![John\_Mace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_mace/32/185_2.png) [@John\_Mace](https://boards.straightdope.com/u/John_Mace)\ **Post date:** [April 20, 2006, 5:57am UTC](https://boards.straightdope.com/t/what-caused-the-pleistocene-holocene-extinction-human-hunters-or-climate-change/353398/7 "2006-04-20T05:57:16Z")
> [@Frank](#): > > I’d say that the wikipedia article was written by an amateur, or by a pro doing an extremely poor job of talking down. > > It is, however, a very interesting question to many of us amateurs, and I’ll be fascinated to follow the argument when those who actually do know what they are talking about pick up this thread. \*\*Colibri \*\*already did that. > [@](#): > > Even if it’s just to say, “Umm, dunno.” You’re fascinated by people saying “umm, dunno”? 🙂 ---
**Author:** ![Frank](https://avatars.discourse-cdn.com/v4/letter/f/3d9bf3/32.png) [@Frank](https://boards.straightdope.com/u/Frank)\ **Post date:** [April 20, 2006, 6:08am UTC](https://boards.straightdope.com/t/what-caused-the-pleistocene-holocene-extinction-human-hunters-or-climate-change/353398/8 "2006-04-20T06:08:03Z")
> [@John Mace](#): > > \*\*Colibri \*\*already did that. **Colibri** did not make any arguments of his own, but merely linked to two sources. Do you believe there are no sources/no scientists which/who disagree? Of course not. If it turns out that **Colibri** ’s links do reflect a concensus of “I dunno”, yes, I will be interested in that, as it overturns what I thought I knew. ---
**Author:** ![Khadaji](https://avatars.discourse-cdn.com/v4/letter/k/9e8a1a/32.png) [@Khadaji](https://boards.straightdope.com/u/Khadaji)\ **Post date:** [April 20, 2006, 10:34am UTC](https://boards.straightdope.com/t/what-caused-the-pleistocene-holocene-extinction-human-hunters-or-climate-change/353398/9 "2006-04-20T10:34:30Z")
Could man also have carried diseases for which these mammals had no natural defenses? ---
**Author:** ![Sailboat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sailboat/32/461_2.png) [@Sailboat](https://boards.straightdope.com/u/Sailboat)\ **Post date:** [April 20, 2006, 1:09pm UTC](https://boards.straightdope.com/t/what-caused-the-pleistocene-holocene-extinction-human-hunters-or-climate-change/353398/10 "2006-04-20T13:09:23Z")
Was the climate change at the time of the extinctions siginifcantly greater than the previous climate changes of the Ice Age fluctuations? I was under the impression that the ice had advanced and retreated many times over a long period (40,000 years is the number in my memory, but take it with a grain of salt, please). If the megafauna did not die out in previous similar climate changes…and large animals are (very generally) well suited to cool climates due to their favorable surface-area-ratio making it easier to retain heat…and man’s arrival DOES coincide with the extinctions…then is there persuasive evidence that climate change was really responsible? The timing of human presence seems to match the extinctions, which would seem to make climate change a far-fetched coincidence, and we know how capable humans are of driving extinctions. I had been under the impression that the debate was primarily whether human hunting or human disease introduction were responsible, not _whether_ humans did it but _how_ they did it, in other words. Are these scientists paleontologists, trying objectively to isolate the cause for extinctions, or are the climatologists looking for grant money? 😉 Okay, that was evil of me. But I do wonder about researcher objectivity at times. If your only tool is a hammer, every problem looks like a nail. If you’re a climatologist… For one thing, there’s a political movement afoot these days to de-emphasize the damaging effects humans have had on the enivornment and say “it’s all a natural climate cycle”: see Bush, Rove et. al.: _Everything is Peachy, Go Back to Sleep: God Did It_, Volume I, 2000-2006. Sailboat ---
**Author:** ![John\_Mace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_mace/32/185_2.png) [@John\_Mace](https://boards.straightdope.com/u/John_Mace)\ **Post date:** [April 20, 2006, 1:51pm UTC](https://boards.straightdope.com/t/what-caused-the-pleistocene-holocene-extinction-human-hunters-or-climate-change/353398/11 "2006-04-20T13:51:43Z")
> [@Sailboat](#): > > I had been under the impression that the debate was primarily whether human hunting or human disease introduction were responsible, not _whether_ humans did it but _how_ they did it, in other words. Nope. It may have been painted that way by the popular press, or by some Discover Channel show, but scientists have never ruled out climate change as a cause, or one of the causes. > [@](#): > > Are these scientists paleontologists, trying objectively to isolate the cause for extinctions, or are the climatologists looking for grant money? 😉 Did you go to the links given? Here are the very first few words of the first link: > [@](#): > > A University of California, Berkeley, paleobiologist… This is a multidisciplinary study, but there are plenty of biologists involved. > [@](#): > > Okay, that was evil of me. But I do wonder about researcher objectivity at times. If your only tool is a hammer, every problem looks like a nail. If you’re a climatologist… > > \ > > For one thing, there’s a political movement afoot these days to de-emphasize the damaging effects humans have had on the enivornment and say “it’s all a natural climate cycle”: see Bush, Rove et. al.: Everything is Peachy, Go Back to Sleep: God Did It, Volume I, 2000-2006. It’s always good to question things, but research into this issue long predates the present administration and will keep going after Bush is safely retired in Crawford, TX. If you have some tangible info that these particular scientists have a politcal agenda, that would be interesting to see. It’s certainly not out of the question, and we have seen cultural bias slip into anthroplogical research over the years, but I don’t see it in this case. ---
**Author:** ![jshore](https://avatars.discourse-cdn.com/v4/letter/j/b5e925/32.png) [@jshore](https://boards.straightdope.com/u/jshore)\ **Post date:** [April 20, 2006, 1:58pm UTC](https://boards.straightdope.com/t/what-caused-the-pleistocene-holocene-extinction-human-hunters-or-climate-change/353398/12 "2006-04-20T13:58:55Z")
> [@Sailboat](#): > > Was the climate change at the time of the extinctions siginifcantly greater than the previous climate changes of the Ice Age fluctuations? I was under the impression that the ice had advanced and retreated many times over a long period (40,000 years is the number in my memory, but take it with a grain of salt, please). Yes, the earth has been locked into its current ice age - interglacial cycles for about the past 2 million years. Roughly speaking, the cycle for the last ~million years has been about a 100,000 year cycle (i.e., interglacial periods occur about once every 100,000 years) although in the previous ~million years before that, the dominant cycle period was more like 40,000 years. [There are cycles involving the earth’s orbit found at both these frequencies that are believed to serve as triggers for the climate change…although it is not understood why it primarily followed one frequency for a while and then switched to predominantly following the other frequency.] Anyway, the short answer is that if climate change alone is responsible, you are right that there wasn’t anything particularly special as far as I know about the most recent change from glacial to interglacial climate. On the other hand, I wonder if the relative recentness of this change means we have more fossil data on extinctions than we have for the previous transitions. I.e., is it possible that the previous transitions saw similar levels of extinction but that we just don’t have as detailed a record as one goes further back in time, or is it clear that this last transition had a much higher extinction rate than the previous ones? ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [April 20, 2006, 3:59pm UTC](https://boards.straightdope.com/t/what-caused-the-pleistocene-holocene-extinction-human-hunters-or-climate-change/353398/13 "2006-04-20T15:59:43Z")
> [@jshore](#): > > On the other hand, I wonder if the relative recentness of this change means we have more fossil data on extinctions than we have for the previous transitions. I.e., is it possible that the previous transitions saw similar levels of extinction but that we just don’t have as detailed a record as one goes further back in time, or is it clear that this last transition had a much higher extinction rate than the previous ones? It’s extremely clear that the most recent extinction was exceptional in its extent. From Barnosky et al: > [@](#): > > Fifty thousand years ago, continents were populated with more than 150 genera of megafauna (animals 944 kg) (1–4). By 10,000 years ago, at least 97 of those genera were gone (Fig. 1, Table 1, and table S1) . Note that this is _genera_, not species. Genera take longer to differentiate than species, so one would expect that many would be several million years old (and thus predate the Pleistocene itself). For nearly two thirds of genera to become extinct over such a short period is truly astonishing. > [@Frank](#): > > If it turns out that Colibri’s links do reflect a concensus of “I dunno”, yes, I will be interested in that, as it overturns what I thought I knew. What did you think you knew? I wish I could link directly to the Barnosky article, but I believe it requires a subscription to Science. In any case, here’s a quote that sums up part of the conclusions: > [@](#): > > Current State of the Evidence > How far has the debate about Pleistocene extinction on continents progressed in the last 40 years? The case for humans contributing to extinction is now much stronger than it was in the early days, with support from recent work on chronology, simulations, paleoclimatology, paleontology, and archaeology. Yet it is an oversimplification to say that an abrupt wave of hunting-induced extinctions swept continents right after first human contact. Instead, the evidence shows that blitzkrieg sensu stricto can be firmly rejected in western Europe, Siberia, Alaska, and probably Australia and central North America. Without late Pleistocene climatic change, it is likely that species such as horses in Alaska and mammoths and giant Irish deer in central Eurasia would have survived longer, despite the presence of humans. \*\*The recent information now points toward humans precipitating the extinction, but also to an instrumental role for late Pleistocene climatic change in controlling its timing, geographic details, and perhaps magnitude. \*\*The mechanism for climatic effects is likely to be found in detailed species-by-species analyses (19), rather than in one of the three existing global ecological models (10, 59, 60), none of which is fully consistent with observations. Bolding mine. The conclusion that more than one factor was involved does not translate into a conclusion that “We dunno.” Instead, as is usual in ecology, it turns out that the actual situation is more complex than simple scenarios can account for. ---
**Author:** ![ralph124c](https://avatars.discourse-cdn.com/v4/letter/r/8797f3/32.png) [@ralph124c](https://boards.straightdope.com/u/ralph124c)\ **Post date:** [April 20, 2006, 4:12pm UTC](https://boards.straightdope.com/t/what-caused-the-pleistocene-holocene-extinction-human-hunters-or-climate-change/353398/14 "2006-04-20T16:12:26Z")
Lets see: horse, wooley mammoths, sabretooth tigers and giant sloths didn’t survive in the new World. I could understand all of these animals having trouble, except for horse-the feral horses in the Western USA seem to survive very well, even given the human population pressures. Horses seem to thrive in varied climates, and can eat a wide variety of forage. I find it hard to accept that humans wiped them out. Or is it possible that soem didease caused a mass die off? The giant sloth is an interesting case-I’ve heard that a few may have survived 9in remote areas of patagonia) into historic times. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [April 20, 2006, 4:25pm UTC](https://boards.straightdope.com/t/what-caused-the-pleistocene-holocene-extinction-human-hunters-or-climate-change/353398/15 "2006-04-20T16:25:32Z")
> [@ralph124c](#): > > Lets see: horse, wooley mammoths, sabretooth tigers and giant sloths didn’t survive in the new World. I could understand all of these animals having trouble, except for horse-the feral horses in the Western USA seem to survive very well, even given the human population pressures. Horses seem to thrive in varied climates, and can eat a wide variety of forage. I find it hard to accept that humans wiped them out. Your conclusion seems to be the opposite of what the evidence suggest. If horses can survive in a variety of climates, and if they today can thrive in an area where they were formerly wiped out (the western US), then how could climate change have caused their extinction? One would think that some other factor must have been involved. > [@](#): > > Or is it possible that soem didease caused a mass die off? This has been proposed, but there is little evidence for it, and it seems unlikely due to the taxonomic diversity of animals involved (which included not only a great variety of mammals but also large birds and reptiles). ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [April 20, 2006, 5:57pm UTC](https://boards.straightdope.com/t/what-caused-the-pleistocene-holocene-extinction-human-hunters-or-climate-change/353398/16 "2006-04-20T17:57:58Z")
> [@Frank](#): > > **Colibri** did not make any arguments of his own, but merely linked to two sources. Do you believe there are no sources/no scientists which/who disagree? Of course not. Some researchers continue to disagree. One is [Paul S. Martin](http://www.americanscientist.org/template/BookReviewTypeDetail/assetid/50748;jsessionid=aaa-IlTXtJhQiS), who originated the Pleistocene Overkill hypothesis more than 20 years ago, and who still thinks that human hunting is the primary explanation. (Although even Martin, I think, concedes that climate change had some effect.) There are others who continue to argue the primacy of climate change > [@](#): > > If it turns out that **Colibri** ’s links do reflect a concensus of “I dunno”, yes, I will be interested in that, as it overturns what I thought I knew. I would not say that Barnosky et al.'s article represents a consensus, exactly, since there are still a fair number of people with different views on either side. However, it is a review article (rather than original research), published in the most prestigious scientific journal in the US. As such it can be assumed to represent a relatively objective synthesis of the existing state of knowledge on the subject. ---
**Author:** ![jshore](https://avatars.discourse-cdn.com/v4/letter/j/b5e925/32.png) [@jshore](https://boards.straightdope.com/u/jshore)\ **Post date:** [April 20, 2006, 6:59pm UTC](https://boards.straightdope.com/t/what-caused-the-pleistocene-holocene-extinction-human-hunters-or-climate-change/353398/17 "2006-04-20T18:59:47Z")
> [@Colibri](#): > > There are others who continue to argue the primacy of climate change. Given what you said in response to my question, I don’t see how these folks can stick to this notion (although it may hinge on what they mean by “primacy”). I.e., have these folks identified any way in which the climate change into the Holocene was fundamentally more difficult on flora and fauna than the previous glacial – interglacial transitions? My impression is that there was nothing particularly distinctive about it from a climatological point-of-view, although I could be wrong. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [April 20, 2006, 8:00pm UTC](https://boards.straightdope.com/t/what-caused-the-pleistocene-holocene-extinction-human-hunters-or-climate-change/353398/18 "2006-04-20T20:00:36Z")
> [@jshore](#): > > Given what you said in response to my question, I don’t see how these folks can stick to this notion (although it may hinge on what they mean by “primacy”). I.e., have these folks identified any way in which the climate change into the Holocene was fundamentally more difficult on flora and fauna than the previous glacial – interglacial transitions? My impression is that there was nothing particularly distinctive about it from a climatological point-of-view, although I could be wrong. As far as I am aware, there was nothing at all exceptional about the most recent transition between glacial and interglacial conditions compared to earlier ones, except for the presence of advanced humans with a sophisticated tool-using culture. The fact that many taxa that had survived earlier episodes died out in the most recent one is is in fact one of the strongest lines of circumstantial evidence implicating humans. ---
**Author:** ![Ale](https://avatars.discourse-cdn.com/v4/letter/a/f19dbf/32.png) [@Ale](https://boards.straightdope.com/u/Ale)\ **Post date:** [April 20, 2006, 10:28pm UTC](https://boards.straightdope.com/t/what-caused-the-pleistocene-holocene-extinction-human-hunters-or-climate-change/353398/19 "2006-04-20T22:28:02Z")
May I toss 2 cents in the ring? It would be a compelling case to the (mostly) human caused extintion if it can be stablished that a sizable proportion of the extinct animals fit within the group of animals humans hunted; mammoths, some species of large deer and moas fit the bill in that aspect. My take on this is that humans and animals at the end of the glaciar period were put on a fragile situation, humans had the edge (more than often the silex edge of a spear) to survive under uncertain conditions by preying on the large mammals at hand. The ecologically strained stocks of megafauna just needed a little poke to spiral into extinction. ---
**Author:** ![Spoke](https://avatars.discourse-cdn.com/v4/letter/s/a88e57/32.png) [@Spoke](https://boards.straightdope.com/u/Spoke)\ **Post date:** [April 20, 2006, 10:37pm UTC](https://boards.straightdope.com/t/what-caused-the-pleistocene-holocene-extinction-human-hunters-or-climate-change/353398/20 "2006-04-20T22:37:35Z")
> [@Colibri](#): > > If horses can survive in a variety of climates, and if they today can thrive in an area where they were formerly wiped out (the western US), then how could climate change have caused their extinction? One would think that some other factor must have been involved. And the same point could be made about mammoths, which also were surprisingly adaptable. Their remains have been found as far south as [Guatemala](http://www.unesco.org/culture/latinamerica/html_eng/chapter12/chapter4.htm), which would have been warm and lush even during glacial periods. People seem to have the misconception that mammoths only thrived in cold climates. Those critters were all _over_ the place. (Mammoths and mastodons were also wandering around [Florida](http://www.paleodirect.com/lm15-016.htm), for example.) Given their apparent adaptability, my money is on hunting by paleo-Indians as the primary driver of mammoth extinction. [Next page](https://boards.straightdope.com/t/what-caused-the-pleistocene-holocene-extinction-human-hunters-or-climate-change/353398.md?page=2)