Most Media Outlets Misreport A New Study Linking Interstadials with Pleistocene Megafauna Extinctions

A new study of Pleistocene megafauna extinctions published in the latest issue of Science received considerable publicity.  Most of the media outlets misrepresented the study’s conclusions.  Perhaps journalists were confused by the title of the article: “Abrupt Warming Events Drove Late Pleistocene Holarctic Turnover.”  The overwhelming majority of media outlets reported that the study suggests climate, not overhunting by man caused the late Pleistocene megafauna extinctions.   None of these journalists must have read the abstract because the last sentence of it concedes that man played an important role in megafauna extinctions.  The following passage is the last sentence of the abstract (capital letters mine).

The presence of many cryptic biotic transitions prior to the Pleistocene/Holocene boundary revealed by ancient DNA confirm the importance of climate change in megafaunal population extinctions and suggests that METAPOPULATION STRUCTURES NECESSARY TO SURVIVE SUCH REPEATED AND RAPID CLIMATE SHIFTS WERE SUSCEPTIBLE TO HUMAN IMPACTS.”

This means the authors of this study believe rapid climate change reduced and scattered megafaunal populations, making them more vulnerable to human hunting.  They make it clear that humans were ultimately responsible for the megafauna extinctions in the last 2 sentences of the main body of this study.

Human presence could have had a major and negative impact on metapopulations by interrupting subpopulation connectivity, especially by concentrating on regular pathways between resource-rich zones, potentially leaving minimal sign of direct hunting.  By interrupting metapopulation processes (i.g. dispersal, recolonization), humans could have both exacerbated regional extinctions brought on by climate change and allowed them to coalesce, potentially leading to the eventual regime shifts and collapses observed in megafaunal ecosystems.  The lack of evidence for longer such ecological shifts during earlier periods of the glacial (i.g. >45 kyr) when interstadial events were known, but humans were not, suggests a synergistic role for humans in exacerbating the impacts of climate change and extinction in terminal events.”

The authors of this study collected no original data.  Instead, they analyzed data already available from previous studies.  They plotted climate data from Greenland Ice Cores with studies of megafauna DNA that determined changes over time in population structures.  (Scientists can determine past average annual temperatures by analyzing oxygen isotope ratios in Greenland ice cores that go back 100,000 years.  These ice cores have annual rings from summer glacial melt.)  The scientists used genetic data from 31 species, including 2 from North America (mastodon and elk), 3 from Beringia, and 26 from Eurasia.  They found a close correlation between sudden warming pulses, known as Dansgaard-Oeschger Events, and reduced populations and local extinctions of megafauna.   Dansgaard-Oeschger Events precipitated interstadials (warm climatic phases) within the Ice Age that lasted for 1-3 thousand years.  In some regions some species of megafauna became locally extinct.  Later, when the climate returned to a cooler more arid stage, different clades of the same species recolonized these regions from relic refugia where they found suitable habitat during the interstadial.

DO and Heinrich events

Chart showing Greenland Ice Core data.  This data shows past average annual temperature fluctuations.  The arrows point to Dansgaard-Oeschger Events–abrupt warming events that caused brief interstadials during the Ice Age.  Prior to the appearance of Homo sapiens in Europe, these interstadials were not associated with local extirpations of megafauna species.  But after modern man colonized Eurasia, various species of megafauna did suffer local extinctions following Dansgaard-Oeschger events.  Sudden climate change made these species more vulnerable to human overhunting, according to the study linked below.

Populations of megafauna remained stable during stadials, the cold phases of the Ice Ages, because the environments they lived in were static.  Stadials were longer lasting than interstadials, and open grassy plains prevailed for millennia.  The megafauna became adapted to living in these environments.  But rapid warming with increased precipitation caused dramatic changes to the environment.  Unproductive spruce forests started expanding, and this fragmented and reduced grassland habitat, forcing megafauna to migrate longer distances for suitable pasturage.  They followed the same routes between pastures, making them easier for humans to ambush.

I have a couple quibbles with this study.  First, I think this study is not applicable to North America.  The overwhelming majority of genetic data is from Eurasian populations of megafauna.  Just 2 North American species were used–a database that is far too small upon which to base any conclusions.  Moreover, I hypothesize mastodon populations likely increased during interstadials because they were a semi-aquatic species that favored wetland habitat.  Warm wet interstadials caused wetlands to expand. The scientists involved in this study used genetic data from just a single population of mastodons.  I’m extremely skeptical that mastodons declined in abundance when wetland habitat expanded.

Second, the authors note woolly mammoths survived later in Eurasia than in North America, despite having a longer exposure to human hunting there.  I assume they were making the point that climate played a greater role than human hunting in regulating megafauna populations.  Indeed, a radio-carbon date of 9760 BP from a woolly mammoth rib found in northern Russia is more recent than a 10,800 BP date from the latest mammoth specimen from continental North America.  However, the latter very likely does not represent the last mammoth that ever lived in North America, and sedaDNA from Alaska permafrost suggests mammoths still lived in Alaska 9000 calendar years ago.  Mammoths may have lasted longer in North America–there just isn’t enough data to know for sure.  It’s unlikely that the absolute last mammoth was preserved.  Moreover, northern Russia was probably uninhabited or more sparsely inhabited than most of North America during the late Pleistocene, rendering the author’s point moot.

Reference:

Cooper, Alan; et. al.

“Abrupt Warming Events Drove Late Pleistocene Holarctic Megafaunal Turnover”

Science 2015

http://www.researchgate.net/publication/280302381_Abrupt_warming_events_drove_Late_Pleistocene_Holarctic_megafaunal_turnover

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12 Responses to “Most Media Outlets Misreport A New Study Linking Interstadials with Pleistocene Megafauna Extinctions”

  1. TheAmphicyon Says:

    Your taking a small part of the article out of context. The data showed the warming had more of an impact on wildlife than humans. Blitzkrieg theory is outdated even by Paul S. Martin’s standard. To disprove his theory we have late surviving fauna AFTER humans arrived in the Americas and humans arriving at an earlier date and faunas that died out long before humans arrived. All of these have been proven, humans are known to have arrived in New Mexico at least 18,000 to 20,000 years, in Texas it’s 15000 years. You already reported late surviving fauna living up to 8,000 years ago. Even that giant terror birds died in North America more than a million years ago. So if humans were the cause we would have seen extinction 20,000 years ago in the Americas and there may be earlier human colonization as far as we know. Here’s two others for you, the giant deer in Eurasia survived on the mainland east of the Urals until 4000 years ago and modern humans in Eurasia coexisted with extinct fauna for more than 30000 years. Australia has already disproven their extinctions by finding their mega-fauna had mostly gone extinct more than 100,000 years ago, at least 50,000 before humans arrived there. Africa and Southern Asia kept their mega-fauna. If you want Blitzkrieg than you can cite New Zealand or other islands, otherwise the researchers have indicated they will continue to look for data to buttress an already provable theory, that humans were a secondary or minor component of late Pleistocene extinctions.

  2. markgelbart Says:

    It wasn’t a small part of the article. It was the entire last 2 paragraphs.

    Humans are not known to have arrived in New Mexico 18,000-20,000 years ago. There is no solid evidence of humans in North America until ~14,000 BP.

    Australia (? the continent) has not disproven humans caused extinctions there. There is no concrete data that Australian megafauna became extinct 50,000 years before humans arrived.

    It sounds like you misunderstand some scientific papers or are sadly misinformed.

    BTW, I’m convinced humans are responsible for megafauna extinctions, but I don’t agree with the blitzkrieg scenario. I believe in a protracted overkill scenario that took place over thousands of years. That makes more sense.

    If you remove humans from the equation, most species of megafauna would still be extant. That means humans are 100% responsible for megafauna extinction, not climate change.

    See this article about this study. This study showed a high correlation between the arrival of humans and megafauna extinction. https://twilightbeasts.wordpress.com/2015/08/14/did-humans-wipe-out-the-megafauna/

    • TheAmphicyon Says:

      arch 2011 > Waters et al., 331 (6024): 1599-1603

      Prev | Table of Contents | Next
      Science 25 March 2011:
      Vol. 331 no. 6024 pp. 1599-1603
      DOI: 10.1126/science.1201855

      Report

      The Buttermilk Creek Complex and the Origins of Clovis at the Debra L. Friedkin Site, Texas

      Michael R. Waters1,*, Steven L. Forman2, Thomas A. Jennings3, Lee C. Nordt4, Steven G. Driese4, Joshua M. Feinberg5, Joshua L. Keene3, Jessi Halligan3, Anna Lindquist5, James Pierson2, Charles T. Hallmark6, Michael B. Collins7, James E. Wiederhold3

      +
      Author Affiliations

      1Center for the Study of the First Americans, Departments of Anthropology and Geography, Texas A&M University, 4352 TAMU, College Station, TX 77843–4352, USA.
      2Luminescence Dating Research Laboratory, Department of Earth and Environmental Sciences, 845 West Taylor Street (m/c 186),University of Illinois, Chicago, IL 60607–7059, USA.
      3Center for the Study of the First Americans, Department of Anthropology, Texas A&M University, 4352 TAMU, College Station, TX 77843–4352, USA.
      4Department of Geology, Baylor University, One Bear Place no. 97354, Waco, TX 76798–7354, USA.
      5Department of Geology and Geophysics, Institute for Rock Magnetism, University of Minnesota, Minneapolis, MN 55455–0219, USA.
      6Department of Soil and Crop Science, 2474 TAMU, Texas A&M University, College Station, TX 77843–2474, USA.
      7Department of Anthropology, Texas State University, 232 Evans Liberal Arts, San Marcos, TX 78666, USA.

      ↵*To whom correspondence should be addressed. E-mail: mwaters@tamu.edu

      Abstract

      Compelling archaeological evidence of an occupation older than Clovis (~12.8 to 13.1 thousand years ago) in North America is present at only a few sites, and the stone tool assemblages from these sites are small and varied. The Debra L. Friedkin site, Texas, contains an assemblage of 15,528 artifacts that define the Buttermilk Creek Complex, which stratigraphically underlies a Clovis assemblage and dates between ~13.2 and 15.5 thousand years ago. The Buttermilk Creek Complex confirms the emerging view that people occupied the Americas before Clovis and provides a large artifact assemblage to explore Clovis origins.
      Okay that’s the Texas evidence and facts.

    • TheAmphicyon Says:

      Give me a reason you think fauna in Africa and southern Asia survived. If it’s protracted overkill it would stand to reason these areas would have been empty of large wildlife long before Europe, Australia, Americas.

      • markgelbart Says:

        You claimed in your original post that there was evidence humans were in New Mexico 18,000-20,000 years ago. Those are the dates I took issue with. The paper you cite suggests humans were in Texas somewhere between 13,200-15,500 years ago. 15,500 years ago is the earliest they might have been in Texas, but that is the earliest end of an estimate. That doesn’t mean they were actually in Texas that early and is certainly not concrete evidence they were there that early. According to this study, humans may not have arrived in Texas until the later end of the estimate…13,200 BP

        Tropical diseases have always kept human populations low in Africa and southern Asia. In fact, large areas of these continents remained uninhabited or scarcely inhabited until well into the 19th and 20th centuries. Human populations remained low enough so that megafauna populations were not negatively impacted. Malaria, tsetse flies, etc. helped protect the megafauna there.

      • TheAmphicyon Says:

        Southern Asia had large settled populations for centuries going back 5000 years, even the Indus valley civilization existed back over 4000 years and Southeast Asia already had civilizations going back centuries and India at present has over a billion people today. That doesn’t cut it because they still have large game there. The Texas evidence you just dismissed out of hand, you diminished it with no valid reason. If it’s over 13000 or 15000 doesn’t matter it’s older as is Monte Verde in South America. DNA already proved that Native Americans split 13000 years into two groups and is as old as 23000 years old. Hope you don’t believe in the Clovis first theory because it’s already been debunked. Your implying that the rest of the world had such large populations of people that they had such great numbers over southern Asia and Africa where humans originated that they wiped out animals because disease didn’t hold down their numbers is based on what numbers? Makes no sense, you assume humans exploded to wipe out wildlife, yet big game persist for centuries in regions were people regularly hunted them for food, skin, ivory, sport, and protection. Even in Africa they had metal, cattle, and settled populations who farmed, even more so in Southern Asia. Apparently ice age humans with no domesticated animals except a dog and no farming/pastoral with smaller numbers and much more primitive weapons made of sticks and stones were far more deadly than any of the later more developed people of Africa/Asia with greater number, cities, villages, trade networks, cattle, sheep, goats, horses (Asia), water buffaloes, and the wheel. I believe your seeing humans today and assume they had the same impact in the past which is wrong, we didn’t have the technology or numbers back then, but if you want to go blame humans at least be consistent and realize mega fauna should have been wiped out earlier in regions were not just humans but other hominids had been in for over 2 million years.

  3. markgelbart Says:

    Yes, there were ancient civilizations in Africa and south Asia, but there were also large regions of those continents that were largely uninhabited or scarcely inhabited until very recently. The Hindus in India hold life sacred and have had a long history of not killing animals, explaining why large game still persists there despite the high population.

    I didn’t dismiss the Texas evidence out of hand. I was attempting to explain to you that the study was based on stratigraphical evidence, not radio-carbon dating. The artifacts they found there could in fact be as recent as 13,200 BP, thus debunking your certainty the study found artifacts that prove humans were there 15,000 BP.

    I don’t believe in the Clovis first theory which nevertheless has nothing to do with anything I’ve written about protracted overkill.

    DNA evidence does not prove “Native Americans split 13,000 years into two groups and is as old as 23,000 years old.”

    This statement is an example of you misunderstanding the results of some scientific studies. DNA evidence suggests the ancestors of Native Americans split with ancient Siberians in east Asia 23,000 BP. They were still living in east Asia when this divergence occurred. It’s not proof Native Americans occurred in North America that long ago.

    You claim what I write “makes no sense.” Yet, I can’t make heads or tails out of half your sentences. Go take a course in grammar before writing on my blog again.

    BTW, please learn the difference between you’re and your.

    • TheAmphicyon Says:

      You’re just attaching yourself to a modified Blitzkrieg theory, plain and simple. Instead of a quick death it’s a slow death, yet you haven’t given any evidence on how to measure extinction in the short run vs. over thousands of years. You can’t quantify it, hence you make up stories that no one can verify, at least I cited RECENT studies not outdated articles published by non-scientific laypeople. I’ll stick to the articles in scientific journals and you can keep writing your fantasy blog.

      • markgelbart Says:

        You only cited 1 paper–an archaeology study that had nothing to do with megafauna extinction.

        On this comment section I cited 1 study that focused on megafauna extinction. This study is brand new and was published by scientists in a peer-reviewed scientific journal. If you would have bothered to read it, you would have learned there is a close correlation between human presence and megafauna extinction.

        Here is a direct link to the paper. My previous link was to the lead author’s blog article that discussed the paper in layman’s terms. http://onlinelibrary.wiley.com/doi/10.1111/ecog.01566/abstract

        Moreover, you have demonstrated an inability to understand the content of scientific journals.

      • TheAmphicyon Says:

        How do you create rules by which you can say it was humans when other factors come into play. Pronghorn antelope, let me guess it was too fast for humans to catch, bison (wiped out in most of Asia, but survived here in North America and Europe), yak were found in Alaska but survived in Asia, musk ox too far north even though Greenland and Iceland had been occupied by humans, Llamas and camelids being hunted but survived in South America as well as being domesticated, it’s inconsistent. I could have just commented that those animals adapted to the changes in climate better than the other wildlife. Did it take 10,000 years or 5,000 years to wipe out Woolly Mammoths on the continents even though they coexisted with humans for over 35,000 years (Eurasia), so they just happened to go extinct at a random time. If extinction were occurring at a specific time worldwide, then you assume people did it. Australia has already disproved their extinctions by humans, simply because the extinctions took place over a 100,000 years ago, far earlier than humans arrived. Any and all African and Southern Asian extinctions that did occur had nothing to do with humans since YOU said disease kept human numbers down, European and northern Asian extinctions YOU said were drawn out over thousands of years, and the Americas occurred within the time period 12,000 to 10,000 with some species hanging on later. So in places with no humans we have extinctions (Australia), recent human arrivals extinctions (Americas), little to no extinctions with long term humans (Africa and southern Asia), and long term humans with extinctions (Europe and northern Asia). I still don’t see a pattern, what I would say is that each extinction should not be looked at as a broad pattern, but as an individual case applying to a species. Why did the giant deer survive thousands of years after the other ice age fauna had disappeared is a better question? That humans hunted them out, really, well why do we still have moose running around, both co-existed with humans for thousands of years. There so many exceptions, humans being the major cause of extinctions, TODAY, yes we are, back then hardly.

  4. markgelbart Says:

    Here is an example of your poor writing skills.

    “Australia has already disproved their extinctions, simply because their extinctions took place over 100,000 years ago, far earlier than humans arrived.”

    What do you mean by this? Australia, the continent itself, disproved extinctions? How can a continent prove or disprove anything? It is an inanimate object. And how can extinctions be disproven. Do you mean the species that lived in Australia 100,000 years ago are still alive and are no longer extinct, thus disproving their extinctions?

    Incidentally, I don’t know where you get this bologna. The colonization of Australia by humans 50,000 years ago is closely tied to the extinctions of megafauna there. See: http://onlinelibrary.wiley.com/doi/10.1111/ecog.01566/abstract

    I don’t have time to discuss the extinction or non extinction of every species that has lived since the end Pleistocene, even though I have thought about them and have explanations for each and every one.

    It’s fine if you disagree with me, but I’m not going to waste any more time responding to your incoherent writing.

    • TheAmphicyon Says:

      It’s obvious your biased against any scientific articles that disprove your belief in long term human induced extinctions even going against the proof that Australian megafauna had been wiped out before humans arrived. As I said before I go where science leads and not on outdated science.

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