More on the Collapse

Ironically, just as I was writing my last post, on the Classic Maya Collapse, the Early Edition of the Proceedings of the National Academy of Sciences was releasing online the articles in a special section devoted to historical collapses. It appears to have been organized by Karl Butzer, the doyen of environmental archaeology. The special feature includes two articles on the Maya:

Dunning, Nicholas P., Timothy P. Beach, and Sheryl Luzzadder-Beach (2012). Kax and Kol: Collapse and Resilience in Lowland Maya Civilization. www.pnas.org/cgi/doi/10.1073/pnas.1114838109.

Luzzadder-Beach, Sheryl, Timothy P. Beach, and Nicholas P. Dunning (2012). Wetland Fields as Mirrors of Drought and the Maya Abandonment. www.pnas.org/cgi/doi/10.1073/pnas.1114919109.

I haven't had the chance to read them yet, but the authors are at the top of the field and have already made major contributions to the research on the question, so I expect the articles to be both interesting and important.

Ancient Maya Droughts Caused Collapse of Journalism

Last Friday an article [1] came out in Science on the perennial issue of the role played by drought in the collapse of Classic Maya civilization. Medina-Elizade and Rohling present a quantitative model of precipitation changes using four paleoclimate proxy records from Yucatán: 1) the high resolution (1-yr) δ¹⁸O record from the Chaac stalagmite from the cave of Tzabnah in Tecoh; 2) the lacustrine δ¹⁸O record from Punta Laguna; 3) the lacustrine δ¹⁸O record from Lake Chichancanab; and 4) the sediment density record from Lake Chichancanab. They authors conclude that the Terminal Classic period droughts were somewhat less severe, in part because they were discontinuous, than previously thought. The discontinuities are apparent in the high-resolution data from the Chaac stalagmite but were masked by the coarser temporal resolution of the lacustrine data sets. It’s a nice article. It builds on Medina-Elizade’s impressive work on the Chaac stalagmite [2].

The article generated considerable buzz in the popular press, but the journalists seem to have gotten the message wrong. Most of the newspaper articles have headlines like “Maya Collapse Caused by Drought” when the central message of the article is that the droughts were less severe than previously thought. Moreover, Medina-Elizade and Rohling interpret the isotopic signal to imply that most of the decrease in precipitation resulted from a decrease in tropical storms and hurricanes. (Water from hurricanes has a slightly lighter isotopic content than regular precipitation. Fascinating, no?) While cyclones provide a significant percentage of the total rainfall in the Yucatán Peninsula, they are also deleterious to human settlements and the agricultural economy because they destroy houses and crops and are usually followed (the next year) by huge forest fires (from the dead trees knocked down by the storm) and also sometimes by plagues of locusts. So, not only were the droughts more intermittent than previously believed, but the reduction in cyclonic activity may have actually been beneficial to some degree. Finally, we need to remember than the collapse started before the Terminal Classic droughts, in the west and southwest Maya lowlands (Petexbatun region, Palenque, etc.), where there is essentially no evidence of drought.

An additional interesting observation: an article just came out in the journal Weather in which the authors analyze climate data drawn from Arabic historical documentary sources from Iraq for the period A.D. 816 to 1009 [3]. This period corresponds precisely to the Maya Terminal Classic period. The authors list seven droughts in this period, of which two (A.D. 897 and 913) are approximately contemporaneous with two of the major Maya droughts (A.D. 895 and 909), each of which lasted for several years [see Ref. 2].

So, I’m not saying there weren’t any droughts, but their relationship to the collapse is murky and uncertain. They probably weren’t the essential underlying cause of the collapse, which was almost certainly severe overpopulation that in turn created a critically unstable political, economic, and ecological regime, which was vulnerable to almost any kind of shock—war, drought, or environmental degradation.

References Cited

1. Medina-Elizalde, Martín and Eelco J. Rohling (2012). Collapse of Classic Maya Civilization Related to Modest Reduction in Precipitation. Science 335:956-959.

2. Medina-Elizade, Martín, Stephen J. Burns, David W. Lea, Yemane Asmerom, Lucien von Gunten, Victor Polyak, Mathias Vuille, and Ambarish Karmalkar (2010). High Resolution Stalagmite Climate Record from the Yucatán Peninsula Spanning the Maya Terminal Classic Period. Earth and Planetary Science Letters 298: 255-262.

3. Domínguez-Castro, Fernando, José Manuel Vaquero, Manuela Marín, María Cruz Gallego, and Ricardo García-Herrera (2012). How Useful Could Arab Documentary Sources Be for Reconstructing Past Climate? Weather 67(3): 76-82.

Domestication of Dogs Over 30,000 years ago

In the last couple of weeks, I have seen a stream of news reports gushing about new evidence for the domestication of dogs as long as 33,000 years ago. As far as I can tell, the research they are referring to is this article published in the prestigious open access journal PLoSOne. What seems strange to me is all the fuss about an article that, according to the journal, was published back in July 2011.

Having glanced at the article, I would say that the radiocarbon dating seems unassailable. The other important question is whether the remains are really of a dog or of some other animal. I cannot reliably judge their assertion that it is a dog because the argument is based on an analysis of the evolution of canine cranial physiology, about which I personally know nothing.

If there's another article out there that I missed, let me know. Or if you have any thoughts about how slow the press can be in picking up a story, which then spreads like an epidemic.

Guide for My Graduate Students

Here you will find a helpful guide to my attitudes. I urge you to consult it carefully.

A New and Curious Application of Fractal Mathematics to the Social Sciences

The number and variety of applications of fractals and power laws to the social sciences continues to increase.

Here's one on the power law behavior of the time intervals between murders committed by a Russian serial killer.

What's next? Your guess is as good as mine.

Public Lecture February 23rd at the Palm Beach County Archaeological Society

I will be giving a lecture to the Palm Beach County Archaeological Society entitled “Why Most of What We Think We Know About Archaeology Is Wrong, and What We Should Be Doing Instead.”

I thought about calling it "What I Think about in the Shower" but that seemed open to misinterpretation.

Date: Thursday, February 23rd, 2012
Time: 7:00 pm
Place: West Palm Beach Public Library
Room: 3rd Floor conference room
Address: 411 Clematis Street, West Palm Beach, Fla. 33401


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I will discuss the application to archaeology of the statistical issues raised by John Ioannidis’s famous paper “Why Most Published Research Findings Are False”. I will then discuss the unintended consequences of confirmatory hypothesis testing research designs in archaeology and explain why we should focus our efforts, instead, on hypothesis-generating research. I will conclude with an unusual example that I'm keeping to myself for the moment.

Academic Social Networking Sites

I'm curious to find out what social networking sites other archaeologists are using. I've built a profile at Academia.edu, which seems to be well designed and quite active. There was an article in the New York Times today lauding the Researchgate.net site. I have an account there too, which I created in response to "friend" requests from colleagues. I find the Researchgate site awkward and cumbersome to use.

There are clearly too many social networking sites out there. I must have profiles on at least half a dozen, and I obviously don't keep up with any of them as a result. What site(s) do you use?

New Book Hot Off the Presses

Walter Witschey and I have published a new Historical Dictionary of Mesoamerica in Rowman and Littlefield's historical dictionary series. Yesterday I discovered that it had come out in print when I got a box containing my complimentary copies. Yeah! It's dated 2012, although in fact it must have been physically printed last year. It's a good-looking volume, thanks in part to Walter's skill as a photographer. His photo of the Caracol on the cover came out very nicely. Thanks, Walter, for your collaboration. It was fun!

Here's the URL for the book on the publisher's web site: https://rowman.com/ISBN/9780810871670, or you can click on the title above.

Here's the link to the book on Amazon.com.

Historic Map of the Laguna de Términos

I post below a scan of a historic map of the Laguna de Términos. Some years ago, I lived in Springfield, Virginia, near the Washington, D.C. Beltway. Around Christmas time, a dealer in old maps, prints, and etchings would set up shop at the local mall. I found there an old map of the Laguna de Términos in Campeche. It may be a German copy of Jacques Nicolas Bellin’s map from the eighteenth century. I bought it because it shows the location of an Indian village, apparently named Usumacinta (see detail). I wonder if Dampier mentions it? He was living there not too long before the map would have been made, and of course the map may include details copied from earlier maps. Click on the images to enlarge them. I can provide a higher resolution scan if anyone needs it for research.

Quadrantid Meteor Shower

Last night, I set my alarm clock for 2:15 am and laid out warm clothes for the morning. I was out looking for the Quadrantid meteors by 2:30 am this morning. After about 20 minutes, I hadn't seen a single one, and so I came into the office. Very disappointing! Probably too much light pollution where I live. I thought about driving out to the beach or out to the edge of the Everglades--either one would be much darker than my neighborhood--but I wasn't sure which would be better, and so I did neither.

The last time I saw a good meteor shower was around 1993, in the Yazoo Basin of Mississippi, with Lynn Berg.

Did anyone out there have better luck than I?

Strange first post for the new year. At least I didn't eat any strange brownies from friendly hippies, like the guys in the Big Bang Theory.