Friday, June 27, 2014

Mexican DNA patterns reveal indigenous history and migrations

A major article in Science last week reveals the potential for modern DNA studies to reveal historic patterns of interaction and migration. It has implications for archaeology and especially for the use of ancient human DNA.

Moreno-Estrada, Andrées, et al. (2014). The Genetics of Mexico Recapitulates Native American Substructure and Affects Biomedical Traits. Science 344(6189): 1280-1285.

The authors sequenced large numbers (hundred of thousands) of SNPs (single nucleotide polymorphisms) from about 1000 individuals in Mexico, split between natives and mestizos (although I couldn't find in the article or the supplementary material how they determined who was which). In the data, you can see strong evidence for the genetic substructure of the population. That is, cultural, ethnic, and linguistic groups do have distinctive genetic signatures. For example, the Maya form a distinct group with additional internal structure. Within the Maya "clade" the Lacandon and Tojolobal form especially homogeneous subgroups that display little outside admixture. There's also a widespread "Central or Southern Mexican" clade (medium blue in Figure 2B and C) that impinges on the Maya. This clade is purest in southern Mexico (Oaxaca and environs), where it shows relatively little admixture. Maya genes also flowed into central Mexico (Figure 2B, bottom). In many cases, geography is a better predictor of genetics than language. Note, for example, how Nahua-speaking groups fall into more than one genetic group that is better defined spatially, which makes some sense when you think about actual mechanisms of gene flow. On the other hand, the data does contain genetic evidence of at least a couple of migrations. The most prominent one appears to go from the Yucatan Peninsula to what the authors call the Totonac region. If you plot the latitude and longitude of the sampling location given in the supplementary materials, it seems that it also close to the Huasteca. Whether this genetic contribution comes from the quite ancient Huastec migration or from a more recent Maya incursion, such as the Olmeca-Xicalanca conquest of Cacaxtla, is not addressed. I suspect, however, that the data could in theory be used as a molecular clock to date the migration, at least very roughly. Since the Huastec and Olmeca-Xicalanca migration are far apart in time, even a crude estimate would be sufficient to distinguish between them.

So, for archaeologists, there are a couple of significant facts. These kinds of studies can be used to understand prehistoric population dynamics. This is not news, perhaps. Genetic studies in Europe have been used for years to investigate the spread of agriculture and determine whether it was migration, diffusion, or both, and what the spatial dynamics were. It is interesting, however, to see it working in Mexico, which seems to me to be even more complex. Another important issue this study raises is the potential for ancient DNA to be matched to modern patterns. Presumably now we could take DNA from an archaeological individual and potentially match it preferentially to a "clade" defined by modern genetic distributions. That's an exciting possibility. It would provide far more information than the strontium isotope methods currently in use. Little ancient DNA has been sequenced in Mesoamerica, but now we have even more reason to do it.

Puerto Rican origins and Maize

Nice letter in yesterday's edition of Nature in which the authors point out that maize DNA in human coprolites from Vieques Island off Puerto Rico does not imply an origin in the Bolivian Andes, for the obvious reason that maize was widespread, not to mention that it had already arrived in the area at an earlier date.

Pagán-Jiménez, Jaime R., Reniel Rodriguez-Ramos, and José R. Oliver (2014). Ancient Cultures: Maize is not a clue to Puerto Rican Origins. Nature 510:473.

Friday, June 13, 2014

George Stuart, distinguished Maya archaeologist, has passed away

National Geographic, where he worked for many years, has posted a gracious obituary. He was a truly nice and unpretentious gentleman. Condolences to his friends and family.

Friday, May 30, 2014

Nicaragua trip

Last week, I returned from my first trip this summer to Nicaragua. I was fortunate to be able to spend some time with colleagues, friends, and family.

First, we went to Cusirisna Cave in the Department of Boaco. Kendra Philmon wrote her thesis on the materials in the cave, which are curated at the Harvard Peabody. We are hoping to publish a revision of her thesis as a monograph. At the SAA meetings, she asked me if it were possible that some of the teeth remained on the floor of the cave. Most of the crania in the collection have lost their front teeth. So, I stopped by with my wife to take a look. I also wanted to take more photos because those from my first trip were not great. It was a terrible mistake. Getting to the cave requires a bit of a scramble. It's in a gorge with very steep walls that are paved with loose rock. Moreover, I'm in terrible condition. My wife is in better condition, but she took a serious fall while I got overheated. I managed to get some pictures and take a quick look in the cave.I didn't see any teeth, but I noticed that there is a layer of earth that might conceal additional remains and could be excavated.
Cusirisna Cave. Right hand chamber. Machete points approximately north

Cusirisna Cave. Left-hand chambers

Lahar deposit underlying Cusirisna Cave.
From Cusirisna, we went to the town of Boaco to visit our friend Edgar Espinoza, a semi-retired archaeologist. He has a lovely home there, and he kindly invited us to spend the night.

The next day he took us to see some petroglyphs in the surrounding hills.

Petroglyphs near the base of the hill, Boaco

Petroglyph of a fawn near Las Lagunas, Boaco

Anthropomorphic petroglyph (shaman?) near Las Lagunas, Boaco
A couple of days later, we had the opportunity to visit a couple of sites near Somotillo, in the Department of Chinandega, that had been previously found by Jorge Zambrana and reported by Rigoberto Navarro. We first went to see a couple of sites named Don Noe, after the landowner. We found a historic wall, but we're not sure if it is part of one of the previously reported sites. We chatted with Don Noe, but he did not know where the previously reported prehistoric mound site was located. After I came back and mapped our points, I saw that we were a couple of hundred meters too far north.

Historic wall remnant on the property of Don Noe, southwest of Somotillo, Chinandega

Then we drove back to Somotillo and looped around to cross the Rio Gallo and then came back southwest to its junction with the Rio Negro.  Heading south from El Tejar, we found the site of Los Andinos, which turned out to be impressive. According to the original report, it has over 30 mounds, densely packed. We saw lots of material on the surface, including chert (perhaps heat-treated--see photo below), obsidian, and fine-paste ceramics. The fields with the mounds are being plowed, but fortunately with oxen. Tractors will destroy the mounds in no time. This site has more architecture than any other we have seen to date in the Department of Chinandega.

Artifacts in the road at Los Andinos. Note the dark red chert that may have been heat-treated. The fine paste ceramics are typical of the region, including the red slip and the light grey cores. The compass/clinometer has a centimeter scale on the side.

The largest mound that we saw at Los Andinos, which apparently lies in the northern part of the site.
My wife threw me a surprise birthday party in Somotillo in the Restaurante Katin in Somotillo. I can't remember the last time I had a birthday party, but it must have been when I was a small child. It was also the first time I had a piñata. If you watch shows like America's Funniest Home Videos, you know that gringos are incompetent at whacking a piñata, which is, frankly, embarrassing. I didn't hit anyone or break anything, and I didn't have to dance!

Birthday party at Rancho Katin, Somotillo

Birthday party at Rancho Katin, Somotillo

Whacking the piñata
Adios for now.

Tuesday, May 6, 2014

The Society for American Archaeology annual meeting, and on being a discussant

This year's SAA conference was a lot of fun. My department at FAU boasted a large contingent of current and former graduate students, many of whom presented on their own research, including Kendra Philmon, Kelin Flanagan, Brittany Reneau, April Watson, and Laura Van Voorhies. Tim Guyah and Tom DiVito, recent graduates of our program, also attended the meetings. One of my departmental colleagues, Valentina Martinez, presented on her research in Ecuador.

I was involved in two symposia, one on recent research in Nicaragua and the other on multi-scalar approaches to archaeological interpretation. Both were very interesting. In the Nicaragua session, I presented a brief summary of work to date in the Department of Chinandega and Kendra Philmon outlined our work on the collection from Cursirisna Cave in Boaco. In the multi-scalar session, which included some research involving fractals, Kelin Flanagan presented her work on the fractality and lacunarity of archaeological site distributions. I served as a discussant at that symposium. 

It was my first experience as a discussant, and it was interesting for me. I read all the papers that had been submitted in advance, which seemed a lot like actual work. Then I thought about the remarks I had heard discussants offer in other sessions. They seemed to me to fall into two categories: those that critiqued the papers individually and those that offered thoughts on the theme of the symposium. While the former are probably more common, I though the latter were potentially more interesting. I still remember lucidly the comments that David Pendergast made at a symposium on Maya cave archaeology many years ago. They were of the second type, general observations on cave archaeology. I found his remarks more inspiring and affecting than any of the papers that had been given in the session. With that in mind, I tried to emulate that model of being a discussant. So the night before the session (which captured the enviable Sunday morning time slot), I created a brief presentation on the polyvalent meanings of scale in archaeology. I, at least, thought the comments were interesting, and it of course saved me from summarizing and reviewing everyone else's talks, with the concomitant potential for misinterpretation, omission, and offense.

I would be very interested in hearing about others' experiences as a discussant or your opinions about what kind of comments are most interesting and influential.

Thanks to those who organized our symposia and were kind enough to invite me and my students: Geoffrey McCafferty, Larry Steinbrenner, and James Stemp.

Tuesday, April 15, 2014

No dinosaurs!

I cannot tell you how many times someone has asked me what I do, and after I tell them I'm an archaeologist, he or she asks, "Found any dinosaurs lately?" What's shocking about this is how often the interlocutor is an educated person. I first remember this happening when I was an adolescent and my optometrist thought that archaeology was the study of dinosaurs. In the decades since then, I have learned that this experience was not an anomaly. Many people with graduate degrees do not understand that archaeology is about studying ancient cultures, and therefore is a social science, while paleontology is about studying extinct animals and plants, and is a branch of geology.  There's very little overlap between the two fields, although paleoanthropology (the study of our human ancestors, a sort of paleontology of the human lineage) and certain instances of zooarchaeology come to mind.

I don't know if paleontologists get asked, "Found any pyramids lately?" or, if they do, whether it annoys them.

Perhaps archaeologists are overly sensitive, but being taken for a paleontologist evidently annoys some of us. Here's the video that proves it:

Yes, there's a song about it on Youtube.

But what really takes the cake is that the American Association for the Advancement of Science, publisher of Science, doesn't seem to appreciate the difference. On their science news accumulator site, EurekAlert!, under the category "Archaeology" they brazenly include paleontology articles.

More great science journalism! For shame, AAAS.

Caving in Oaxaca, The Cheve system

An interesting article in the New Yorker on exploring one of the deepest caves on earth, in Oaxaca.

Tonight's Lunar Eclipse, a rare skywatching success

All of you--that is, both of you--who follow this blog should know that I haven't had a lot of success in observing celestial phenomena in the last couple of years. When I manage to wake up for the meteor shower (or whatever), it's usually too cloudy to see anything, or there is too much light pollution, or something. Well, the dry spell finally broke. I saw the lunar eclipse this morning.

Here is the edge of the moon reappearing. Poor photo, but I'm not set up for proper celestial photography.

When the eclipse began, I was tempted to start banging on pots or shooting at the sky to scare off the beast eating the moon, as they do in Yucatan. I didn't think my neighbors would appreciate it, though, so I restrained the impulse.

I still don't understand why I walked to the end of my driveway to see the eclipse better.

Beautiful, clear night, for once. The moon really did turn red, and you could tell because Mars was--brilliantly--right by her side for comparison.

Thursday, March 6, 2014

Atlatl videos

I bought a fancy atlatl at the knap-in last weekend. I've made my own atlatls in the past. It's easy to carve a crude but functional one from a tree branch. In contrast, the one I bought, from Thunderbird Atlatls, is a minor work of art.

My new atlatl
If you're buying a making a spearthrower, the most important consideration is that it fits your hand easily so that your fingers can hold the dart shaft. If your hand is small or your fingers stubby, you should take extra care to ensure that you can use the instrument effectively. 

More importantly, I bought several darts, which are much harder to make than a spearthrower.

Atlatl darts
I took the spearthrower and the darts out for a test drive yesterday with one of my graduate students, Kelin Flanagan.

Here are four short videos of her shooting darts.




Kelin is a natural!

Unfortunately, the best video would not upload, perhaps because of the file size. [Update: I converted the largest file to mpg format, and it uploaded, but Blogger still messed up the resolution.] Also, note that the original videos are much higher resolution than these. I suspect the blogging website reduced the resolution to shrink the file size.