Friday, June 29, 2012

A good day in Mexico: Carbon, thin sections, an index, and chicharron

I received a number of good things by email this morning, including radiocarbon dates, ceramic petrography results, and a completed index for a book! When it rains it pours. Dealing with this stuff left little time for the sherd drawing I am supposed to be doing in the lab. This is the first time I have used a professional indexer for a book. Normally I index my own books, and I like the process. An index is an important tool, and constructing a good index is an intellectual exercise as well as an organizational task. Don't you hate it when a book has a lame, four-page index and you are trying to find some specific information? Don't you REALLY hate it when a book lacks an index entirely? But indexing takes time, and with three co-editors for this book we decided to hire a professional indexer.

This is a good book, buy it, you'll like it. You see, after going on and on in this blog about how most edited volumes in archaeology are worthless, I can't afford to edit a bad book. (Here is my original post on worthless edited volumes, and a later related post). So any volume I edit now must be good, almost by definition (please suspend your critical thinking skills here temporarily).

Random ceramic thin section (internet)
I can't say much about the petrographic results. This is our first batch of ceramic petrographic samples, submitted by my student Julie Novic and done by Jenny Meanwell of MIT. Julie hasn't had time to see how they look. Do our macroscopic paste types match petrographic reality? What about our ceramic types? Do the petrographic data support our hypotheses on ceramic production, exchange and consumption? Julie is working on neighborhoods and urban spatial organization at Calixtlahuaca, using our surface data (and she is my co-author in chapter 1 of the above book). We have another sampling scheme for petrography for the excavated ceramics, and we should get the results before too long. I'm glad customs or airport security didn't get weirded out by the saw blade I carried to Mexico in my luggage!

The most exciting news today was a new batch of radiocarbon results from the University of Arizona AMS lab. This is the first bunch from our second batch of dates. We are waiting for the entire suite to run them through Ox-Cal, but we are also working with the uncalibrated dates, not to assign ages, but to estimate phase lengths. It turns out that my colleagues George Cowgill and Keith Kintigh wrote a handy-dandy program a while ago using monte carlo simulation to estimate likely phase lengths from a suite of radiocarbon dates. We ran our initial batch of 20 dates, and we will run the entire group when they are all done. The simulation results in conjunction with the calibrated dates will give us estimates for the calendar dates of our ceramic phases. I am in the process of bugging George and Keith to actually publish their nice study and their algorithm, which illustrates some features of radiocarbon results that seem counterintuitive to many archaeologists.
I must admit to my occasional surprise when some archaeological analysis or another comes out with excellent results. With so many potential confounding factors, it sometimes seems amazing when we get solid, rigorous, and clean results about things that happened centuries or millennia ago. It is still soon to get too excited, but the dates look great. Angela and I did the ceramic seriation and defined three phases based solely on ceramic type similarities. Then we looked at the seriated deposits stratigraphically and they were almost always in the right order. So two independent types of evidence agree. Now we look at the radiocarbon ages, and lo and behold the ceramic phases plot out in  nice chronological sequence, with only a very small amount of overlap (yes, I know, once we calibrate the dates it will be much messier with lots of overlap. I have the bad fortune of working in a period when the calibration curve goes back on itself and ALL relevant dates have multiple age ranges. This is where the Cowgill/Kintigh procedure will help).

So what could be better than all this stuff arriving first thing in the morning? Well, our lunch at the lab turned out to be fresh chicharron, avocadoes, and double cream cheese (queso de doble crema). It didn't look exactly like this photo from the internet, but we put the stuff into hot tortillas and it doesn't get much better than that! And I did get a few sherds drawn as well.


Stefano Costa said...

Is there a way to buy a digital copy of the book?

Michael E. Smith said...

Stefano- Good question. UA Press hasn't said anything about a digital edition. Since that is a marketing issue, authors (editors) have little input. I have seen links on the pages of some publishers where customers can indicate that they would like to see digital editions of books, but not UA Press.