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Pleistocene Extinctions



New research suggesting the decline of the American megafauna was a combination of both climate change and human hunting happening at the same time. For a long time, there’s been a debate over whether the rapid extinction of so many large American mammals was because of the warming climates after the last Ice Age that turned a lot of grasslands into forests or whether it was because the first human residents of the Americas marching rapidly south through the Americas after being stuck in the Arctic for several thousands years wiped them out through hunting. The most sensible answer was always that it was a combination of the two factors and now it’s pretty clearly the case.

Luckily, there’s no connection between a rapidly warming climate and human interventions decimating wildlife today so we have nothing to worry about.

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  • Gwen

    Hi Erik,

    Any thoughts on the police violence against teachers unions in Oaxaca? They’re talking about it now on the Texas Standard (a public radio program that discusses policy issues in Texas and often in Mexico).

    Seems to me like this whole sad mess is Rheeism taken to its logical end…

    • So the Oaxaca thing is incredibly complicated, far more complicated than anyone on the American left understands (there’s a certain sort of leftist with an interest in Latin America that sees each social movement as the next Che-led revolution and they jump from place to place in the region to focus on a given issue rather than really dive deep into one place or issue). The short version is that a) the leaders of Oaxaca are horrible but b) the Mexican education system is truly abysmal and c) a lot of what the teachers want is to be able to pass their jobs down to their children regardless of training. In rural Oaxaca, which is where this movement really has its strongest base, the schools are incredibly underfunded and the children barely receive any education. The Mexican state of course has completely failed in most of its basic tasks, especially as it comes to the poor. There’s a huge variety of quality among the teachers in these schools. Talking to one who is a very good friend of my wife and who teaches in a rural village, she says she has colleagues who are really committed to education but others who really don’t want to be there or care about educating children but it’s the only hold on something like a middle class they have. This helps explain the desire to pass down the jobs–there just really aren’t other middle-class jobs in Oaxaca outside of working for the government, but these teachers aren’t going to break into that, in no small part of course because of the widespread corruption and nepotism. So the Oaxacan teachers movement is demanding a lot of just causes and fighting against programs that would probably make the situation even worse and my sense is that most of the teachers do believe in the demands, but that there really does need to be widespread and overarching changes in the Mexican education system. More money for the kids and higher salaries are absolutely necessary, but some kind of certification or standards is also not the worst thing in the world.

      But it is a mistake to read this as just neoliberal Rheeism. That’s a part of it, absolutely, but it’s really messy on the ground there.

      • Gwen

        Thanks for the perspective Erik.

        My understanding of Mexico is pretty thin, having only visited once and taken a couple college courses (one a survey course on Mexican political history, and the other on “Latin American Social Revolutions” — yes, I was one of *those* kids in college).

        But the more I learn about that country, the more I realize I don’t know anything. I *kinda* think that I am close to groking things in Northern Mexico, since these states strike me as being *somewhat* similar to South Texas in terms of social strata, culture, etc.

        But Southern Mexico seems like it might as well be on another planet.

        • Southern Mexico and northern Mexico are about as different as Vermont and Mississippi.

          I am going to try and write something on the Oaxaca violence and the teacher reform stuff, but it’s a little hard to find good articles to base it on.

      • BiloSagdiyev

        Thanks. I came to make a stupid sloth joke, but yes, I’d like to hear more about the Mexican teacher situation. My fuzzy guess from a distance is that, maybe reforms are needed, but I bet the saviors who have shown up to call for structural reforms have unpleasant agendas. (My roundabout way of saying Rheeism, I guess.)

        But egads, inherited positions? That’s just nutty.

        • But egads, inherited positions? That’s just nutty.

          It’s not entirely nutty (though it certainly seems to be a bad idea in the form presented, and quite likely in any remotely possible form). There’s a strong tradition in strongly traditional cultures (I am thinking particularly of the noble savages rude mechanicals building trades) of the Northeastern USA of, if not literally passing positions of a certain type down, then at least drawing all new tenants of positions of that type from the families (by birth, marriage, or adoption) of the present tenants. Of course it is assumed (usually correctly: though obviously there’s plenty of room for corruption) that the new plumbers, electricians, etc., will actually have learned their trades and be competent.

          I know at least one third-generation math professor (all at the same elite college!), and have met any number of physicians who come from a long line of physicians; my mother (born 1906) got her teacher training at the same normal school where her mother had; one of the new residents here at the OFH is professor emerita of child development, and one of her sons is professor of the same (but not at the same place); morticians tend to pass their jobs along; etc., etc.

  • Webstir

    On that note Erik, could you run a piece on this:


    I don’t think it’s getting much too attention, but it’s eventual passage is critical to maintaining migration corridors to ensure continued biological diversity in the Northern Rockies. If we mange to make some headway in the next election, it may just have a snowballs chance on earth of getting passed.

  • I’ve read about the North American extinctions in a number of different books, and always been surprised by the resistance to admitting human involvement played a definite role in the extinctions. I can’t find a link with a quick google search, but the fact that mega fauna survived longest on the Caribbean islands humans got to last seems to rule out the argument it was solely environmental.

    I guess for some it goes against the thinking that primitive, non-industrial people lived in harmonious equilibrium with nature, and for others it goes against the idea that human activity can have an impact on the environment, and therefore drill baby drill!

    Politics… strange bedfellows… etc.

    • njorl

      Environmental changes usually just alter how well a species competes. It gets wiped out only because something else fills its niche better, or preys upon it better. The changes have to be pretty damn severe to wipe out multiple species directly.
      The American megafauna not only had to deal with environmental changes, but also the introduction of 2 of the most successful species in the world – humans and wolves.

      • *high fives wolf sitting next to me*

      • DrDick

        Wolves actually evolved in North America and spread to Eurasia across the Bering Land Bridge.

        • njorl

          Canids (cynodictus) originated in N. America.
          Canis Lupus originated in Asia and migrated to N. America with humans.

    • DrDick

      The bigger problem with the original hypothesis that it was all human driven is that all of the Pleistocene megafauna in the northern hemisphere (in Eurasia, as well as in the Americas) went extinct at the same time and humans had been present in Eurasia for tens of thousands of years before that. It is also the case that all of the available evidence shows that human population densities in the Americas during the critical period were extremely low, and unlikely to have a large impact by themselves. It is quite possible that humans played some role, and most archaeologists would not disagree with that, but climate change and habitat loss was far more important, even under this scenario.

  • I was goofing off on the Internet the other day and came across this nuget: a temperature rise of 6C results in a planet Earth that can carry less than a billion people. A temperature rise of 4C is generally considered incompatible with global civilization.

    Humans won’t be going extinct, but there’ll be whole lot fewer of us.

  • Philip

    I assume you’ve already seen this, Erik, but Gizmodo’s continuing their running story tracking the Earth’s honest-to-god immolation over the last 13 months.

    • I actually didn’t know they were updating it. God. Is it too early to start drinking?

      • John Revolta

        It’s always 120 degrees somewhere.

      • Rob in CT

        Phil Plait over at Slate has a similar thing going (he’s reposting each month with the month & monthly temperature anomaly data crossed out and replaced with the newest info.

        Of course, at some point El Nino will go away and we’ll be dealing with people talking about a “pause” or “cooling trend” or somesuch nonsense.

    • This coming apocalypse is really screwing up my retirement planning.

      Looks like the best place to be is somewhere in the middle of the continent, near fresh water, and not near a lot of people.

      The UP of Michigan maybe? Further north?

      • Brett

        Either the upper Midwest by the lakes, or New England. The oceans and lakes can moderate the temperature a lot, and they’ll still get plenty of rainfall.

    • Brett

      Minor nitpick, but it’s the hottest recorded temperature. The Earth itself has had far higher temperatures in the geological past – 25 degrees Celsius global mean temperature in the early Eocene, Cretaceous, and Triassic Eras, and possibly up to 50 degrees Celsius GMT after the “Snowball Earth” era.

      Still not good for us. Maybe Salt Lake City will finally break the 107 degrees Fahrenheit temperature record. It’s supposed to get close to 100 degrees here tomorrow.

  • Brett

    This doesn’t surprise me. Megafauna populations were low and their territories wide even under the best circumstances. If human hunters thinned them out, a bad turn in climate could have pushed them beyond the point where they simply never find mates to breed with successfully in enough numbers to save the species.

    That doesn’t bode well for the elephants, although I think they’ll survive human hunting in diminished form even if nearly all of them are tuskless (which started happening in east African parks in the 1990s).

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