News About the Younger Dryas

I don’t want to write anything really interesting here until the technology gets upgraded…

… but I figure I might as well start puttle little comments about ecological issues here, instead of on my diary.


• Chris Colose, Revisiting the Younger Dryas, RealClimate, July 17, 2010.

The Younger Dryas was, among other things, a sudden cooling event in Europe shortly after the end of the last ice age. In only 20 years, the temperature in Europe dropped about 7 Celsius! It stayed cold for about 1,300 years. In Greenland, the temperature went down 15 Celsius. And then, at the end of the Younger Dryas, temperatures in Europe bounced back just as fast.

Sudden climate changes of this magnitude could have a huge impact on human civilization – just imagine glaciers in the Lake District in England. So, it’s worth learning all we can about this episode. Indeed, some people have suggested that freshwater from melting ice was what brought on the Younger Dryas, by disrupting ocean circulation in the northern Atlantic… which raises the specter of a repeat of this incident sometime soon! Luckily, the chances of that now seem very low. But it’s still good to understand this stuff.

If you haven’t learned a bit about Heinrich events (when icebergs drop lots of rocks on to the floor of the northern Altantic), the Bølling-Allerød warm period that came right before the Younger Dryas, the Last Glacial Maximum or LGM around 20,000 year ago, and the Atlantic meridional overturning circulation or AMOC, Chris Colose’s comments may seem a bit dry and jargonesque. But I find them fascinating!

For one thing, I hadn’t known that people were finding evidence of Younger-Dryas-like episodes at the end of earlier glacial periods, suggesting that these events are in some sense routine, rather than something that requires a freak event like a comet impact to explain. (Yes, some people have argued that a comet was to blame.)

5 Responses to News About the Younger Dryas

  1. Tim van Beek says:

    I suppose that the younger Dryas was too long ago to have any documented impact on any ancient society?

    This question comes to my mind because I am reading Jared Diamond’s “Collapse”, which you mentioned on your diary some time ago, if I remember correctly.

    I’ve read several papers that suggested stochastic resonance as a possible explanation of anomalous but periodically occurring climate changes.

  2. John Baez says:

    Let’s see… the Younger Dryas lasted approximately from 10,800 to 9,500 BC, or between 12,800 and 11,500 years ago. What was going on then? I’ll ask the all-knowing one

    • 7,000 years ago: late Neolithic civilizations, invention of the wheel and spread of proto-writing.

    • 9,000 years ago: Jiahu culture began in China.

    • 9,500 years ago: Çatal Höyük urban settlement founded in Anatolia.

    • 9,000-10,000 years ago: In northern Mesopotamia, now northern Iraq, cultivation of barley and wheat begins. At first they are used for beer, gruel, and soup, eventually for bread.

    • 11,000 years ago: founding of the city of Jericho

    • 12,000 years ago: start of the Holocene epoch and Neolithic Age. Invention of agriculture.

    So, there wouldn’t have been writing around… but some theorize that the Younger Dryas helped trigger the rise of agriculture.

    By the way, I went to Çatal Höyük on my trip to Turkey. They consider it the first city. It’s pretty impressive, given that.

  3. Tim van Beek says:

    …but some theorize that the Younger Dryas helped trigger the rise of agriculture.

    Aha: It’s a simple prejudice of mine that some of the factors that favor the development of societies are:

    – rich fauna and flora, a rich summer that allows agriculture,

    – a harsh winter that favors those who invested in building houses, storing food, domesticating etc.

    – a rich interaction with other societies in the neighborhood, both friendly and otherwise.

    That a moderate deterioration of the environment may actually increase the cultural output of a society seems to be a plausible hypothesis to me (one that Diamond does not consider in his book, at least not in the first half, haven’t read the second one yet).

    • John Baez says:

      While some theorize that the Younger Dryas helped trigger the rise of agriculture, I don’t get the feeling that most researchers agree on this. For example:

      • Natalie D. Munro, Small game, the Younger Dryas, and the transition to agriculture in the southern Levant.

      ABSTRACT: The Younger Dryas, an intense cooling and drying event of global proportions, has been attributed a major causal role in the adoption of agricultural economies in the southern Levant. Here, the impact of the Younger Dryas on human adaptations is evaluated using a small game index that measures the efficiency of human foraging as a proxy for site occupation intensity. The study examines faunal assemblages spanning the agricultural transition and dating to the Early and Late Natufian and Pre-Pottery Neolithic periods (ca. 14,500 to 11,000 Cal. BP). The small game index and other supporting evidence document major fluctuations in human site occupation intensity across this critical phase. Site occupation reached an unprecedented high during the Early Natufian, but quickly reverted to pre-Natufian levels with the onset of the Younger Dryas in the Late Natufian phase. By decreasing site occupation intensity and increasing mobility, the Late Natufians implemented effective demographic strategies to cope with changing resource distributions. In contrast, there is no evidence for intensified resource use or food stress in the Late Natufian, at least in comparison to the Early Natufian phase. Although it is tempting to assign the Younger Dryas a causal role in the adoption of agricultural economies, support for this hypothesis (in the form of food stress and resource intensification) does not currently exist.

      If you’re reading Jared Diamond’s Collapse, you might try two other books that I haven’t managed to read yet. This one sounds very interesting:

      • Joseph Tainter, The Collapse of Complex Societies, Cambridge U. Press, Cambridge, 1990.

      And friend Christopher Lee wrote:

      It just occurred to me that if you haven’t read Tim Flannery’s book, The Future Eaters, I think you would find it fascinating. If you haven’t read it, a quick synopsis: the many lands of Australasia have been the site of an amazing variety of experiments on what human and ecological history looks like under severe resource constraints (e.g. when the Maori wiped out all the moa). Flannery goes way beyond the surface stories of mass extinctions (e.g. Jared Diamond’s book, Collapse) into the detailed data and dynamics of many, many examples both positive and negative. The lessons are often surprising.

  4. Tim van Beek says:

    I’ve got the book by Joseph Tainter, if I get to read it I’ll report back :-)

    Since I think we should also have some fun on this blog, despite the dire topic, I’ll mention the funniest archeological project that I ever heard of, pyramids in California!.

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