May 10, 2007

Taphonomy Thursday

I enjoyed posting information and a photo about my research so much that I decided I should do it more than once a week. Let's face it, I never thought it was possible, but I actually miss teaching. I've taught or TA'ed for the past seven years, and I actually like sharing my excitement about bones with others. So for those of you who appreciate didactic, osteology-related posts, you're going to get twice as many now. For those of you who don't... uhm, sorry. Email me and I'll regale you with stories of mentally challenged people who goose-step on Roman trams. So without further ado...

Taphonomy is the study of what happens to bones after a person is buried. It is a catch-all term for everything from rodent gnawing to the effects of soil pH to the rotation of the cranium. In archaeological situations, taphonomic changes can often mimic pathological conditions. In addition to an understanding of pathologies of the human skeleton, an osteologist has to be familiar with the kinds of changes that the skeletons she's working with underwent in that particular area. Since I am working with a population buried in a very different kind of soil with very different rodents and insects and with very different cultural traditions than Native Americans from the U.S., it took me a couple weeks to get used to the taphonomic changes that I was seeing in the Roman skeletons.

Today, however, I found a clear case of taphonomic change to bone that resulted from cultural practices. The palmar aspect of the left hand of a 50-year-old woman I was analyzing looked like this. You will notice that the third proximal hand phalanx is green, a quite unusual color for normal human bone. After I cleaned this bone, I looked through the excavation notes and found that my guess was correct - an anello di bronzo was found among her metacarpals. The bronze ring that this woman was wearing when she was buried corroded and caused the green stain. The discoloration is most significant on the third proximal phalanx, indicating she was wearing the ring on her middle finger, but it also affected the surrounding metacarpals and phalanges of the left hand and the ischial tuberosity (most commonly known as the "butt bone").

Interestingly, some of the bones of the right hand were also affected, indicating her hands were crossed when she was buried. Hands crossed over the pelvis is a typical repose for individuals from this time period. On her right hand, the first and second metacarpals, however, were not discolored. There are two possible explanations for this: one, that her hands decomposed and these metacarpals were moved (by either rodents or dirt shifting) before the ring corroded; or two, her right hand was crossed over top of her left hand in such a manner as to spare the first two fingers from contacting the bronze ring. Photographs of the body in situ during excavation could help solve this question.

There are many more reasons this particular woman is interesting to me, including a healed fracture of her nose and cranial traits that I have not found in the rest of the population, but I will not engage in narrative biography at this point, lest I be labelled a *gasp* postprocessualist before I've even finished my dissertation.

1 comments:

Lara said...

A postprocessualist OH NO! What would the world come to?!

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