Sunday, March 25, 2012

Megafauna Extinction Caused by Overhunting

In last Friday's issue of Science, there's an article about the demise of the megafauna in Australia. Here's the reference:

Rule, Susan, Barry W. Brook, Simon G. Haberle, Chris S. M. Turney, A. Peter Kershaw, and Christopher N. Johnson (2012). The Aftermath of Megafaunal Extinction: Ecosystem Transformation in Pleistocene Australia. Science 335:1483-1486.

In case you didn't know, I should mention that, like the Americas, Australia had megafauna during the Pleistocene, but instead of mammoths, mastadons, camels, horses, dire wolves, and sabre-toothed tigers, down under they had giant marsupials, such as things resembling huge kangaroos and giant wombats. As in the Americas, the Australian megafauna disappeared near the end of the Pleistocene, and in both places there is a scientific debate about the cause of these massive extinctions. The usual suspects are either climate change and over-hunting by the first human populations, although in North America there has also been a recent flurry of interest surrounding the unlikely hypothesis that a meteor impact caused the die-off. What makes the debate tricky in North America in particular is that humans seem to have arrived (granted that the archaeological dates of the event leave a lot to be desired) at a time of rapid climate change. Therefore, distinguishing between the two causes is difficult because of the chronological overlap. In Australia, the situation is different because human arrived much earlier, well over 40,000 years ago, although (again, like in the Americas) there has also been plenty of dissension about the precise date.

The new article in Science contributes significantly to the Australian debate. The authors studied two cores, analyzing charcoal, pollen, and spores of the Sporormiella fungus. The charcoal told them about the changing regime of fires, the pollen provided information about the vegetation, and the spores, which grew primarily in the dung of the megafauna, allowed them to pinpoint their extinction. The spores disappeared about 41,000 years ago, about the same time that the megafauna are believed to have died out based on a variety a paleontological evidence.

(The use of spores from a fungus growing on the dung may seem like a crazy way to study the megafauna, but it's not novel; it's done in North America too. I once talked to a paleoethnobotanist who was studying plant remains from mammoth dung recovered in the Mid-Atlantic states. I asked her about her sample sizes, and she said something like, "It's not a problem. Their coprolites are huge. We have a warehouse full of poop." I guess when a mammoth took a dump, it created quite a pile. Now imagine herds of them slowly pooping their way across the continent. The dung becomes an ecosystem.)

The importance of the recent article in Science is that the researchers can show, through a high resolution chronological analysis, that the vegetation changes and increased burning came after the extinction, not before, and therefore they were evidently responses to the extinction rather than being related to its cause. Moreover, at the time of the extinction in Australia, they found no evidence of significant climate change. It occurred instead during a period relative climatic stasis. And of course the same megafauna had previously survived much more severe episodes of climate change.

The study adds to the growing evidence that human over-hunting caused the extinction of megafauna in several parts of the world. (New Zealand is another example.) This was probably the case in the Americas as well.

Wednesday, March 21, 2012

Haiti--Lessons for Nonprofits

It's always uplifting to see one of your former students both doing well and making a difference. Isabelle Clérié is a prime example. She studied archaeology with me as an undergraduate and then got a Master's degree in nonprofit management. She has worked in her native Haiti, where she is one of the few people who has been alert to alarming degradation of archaeological and historical sites. She currently works for the Franklin Institute, a major science museum in Philadelphia.

Isabelle recently contributed an insightful essay about the work of nonprofits in Haiti to the blog of Michael Rosen. She explains the situation in Haiti as she has witnessed it, and she advocates three changes to the way most nonprofits have been operating there. She summarizes her points as follows:

  • Be an anthropologist!
  • Work together!
  • Go where the people need you!
Great advice and a very interesting article.

Monday, March 19, 2012

Citizen Science

Nice article on Citizen Science (a.k.a. "Open Science") in the Guardian. I had heard of some, but not all, of these projects. How can we do this in archaeology? Use Google Earth (or some other imagery data set) to find sites? Post pictures of artifacts and have volunteers classify them?

Your thoughts?

Thursday, March 15, 2012

Police Destroy Classic Maya Mortuary Cave in Chiapas

A few days ago, my wife asked me if I had heard the news report on National Public Radio about a cave full of bodies found in Chiapas, Mexico. I hadn't, and my wife's account of the report seemed garbled and contradictory. So, I searched the NPR news site and found the text of the report, which turned out to be garbled and contradictory. Thus, my wife's account was an accurate rendition of what she had in fact heard on the radio. The obfuscatory problem was that they reported a lot bodies that were more than 50 years old but also implied that they might be the cadavers (or maybe skeletons; it wasn't clear) of murdered Central Americans. It all sounded very muddy and improbable.

Now the BBC is reporting that the cave was an archaeological site, and the skeletal remains--of 167 individuals--were prehistoric. Unfortunately, law enforcement apparently collected the remains haphazardly by dumping them into large plastic bags without recording much, if any, spatial or contextual information. That doesn't sound like the right way to conduct a forensic investigation. I can attest without fear of contradiction that it is the wrong way to recover archaeological materials and data. We have probably lost any hope of interpreting the ritual and religious function of the cave because those inferences usually rely to a great extent on the spatial organization of the materials in the cave (see, for example, Medina and Sánchez [2007] and Tiesler [2007]).

This is a shocking and extreme case of police destroying a hugely significant archaeological site, albeit unintentionally. But we should remember that this is a perennial issue in archaeology. Something similar happened with Ötzi, the "Ice Man" found in the Alps. The police manhandled him pretty roughly before they realized he was not old but truly ancient.

In most jurisdictions in the United States, for example, when you find human remains, regardless of how old you may think they are, you are required by law to contact police or the local medical examiner. If you are lucky, they are careful and professional enough not to mess up the site if it is archaeological. In my experience, law enforcement is usually respectful of an archaeologist's opinion, when one has actually found the remains. By the same token, law enforcement personnel probably fear, with some justice, that archaeologists might accidentally mess up a crime scene, and, somewhere, sometime, it probably has happened, although we surely all hope that archaeologists are by default meticulous enough to avoid doing too much damage to medico-legal evidence. I do know cases in which archaeologists on survey have found murder victims, or parts of them. I once worked with a young woman who seemed to be fated to always be the one who found the body parts from Mob hits.

Law enforcement agencies should have a plan in place to coordinate with appropriate archaeological authorities when there is any doubt about the age of remains. When I worked for the Navy in Washington, D.C., I was tasked with working out such protocols with the Naval Criminal Investigative Service. (Yes, that is the same NCIS that is portrayed in the long-running television series starring Mark Harmon. Their building was right next to mine. Both are beautifully restored historic buildings at the Washington Navy Yard, which itself is a National Historic Landmark District. It's worth a visit if you're touring D.C.) The Navy was fortunate to have at that time some thoughtful and effective leaders who worried about such things.

I'm not aware of any guidance or policies promulgated by any body, such as professional societies for example, that deal with this issue. Do you know of policies or protocols for coordination between law enforcement and archaeologists? It's a more important issue than it may seem, as this newest incident in Chiapas sadly illustrates.

References cited

Medina Martín, Cecilia and Mirna Sánchez Vargas (2007) Posthumous Body Treatments and Ritual Meaning in the Classic Period Northern Peten: A Taphonomic Approach, in New Perspectives on Human Sacrifice and Ritual Body Treatments in Ancient Maya Society, edited by Vera Tiesler and Andrea Cucina, pp. 102-119. New York: Springer.

Tiesler, Vera (2007). Funerary or Nonfunerary? New References in Identifying Ancient Maya Sacrificial and Postsacrificial Behaviors from Human Assemblages, in New Perspectives on Human Sacrifice and Ritual Body Treatments in Ancient Maya Society, edited by Vera Tiesler and Andrea Cucina, pp14-44. New York: Springer.