So in the mass-grave sites where we find many skeletons, dozens—and each consisting of around 200 bones and 32 teeth—the complexity of the work and the fastidiousness of the technique with which it has to be performed is multiplied by many times because we have to find each bone and get it to its proper skeleton. We have to trace out the skeletons, and I was very pleasantly surprised by the Argentine team. They came up with an idea that I think is unique: using colored tape as you see in the slide. As you see—using colored tape, little tags of colored tape for each of the commingled skeletons, red for this skeleton, blue for this one, green, yellow, and so forth, and that way, you can keep the skeletons as you're exposing each one, uh…to their mark so that when they are taken up, we avoid the problems of commingling.
Once the bones arrive in the laboratory…they have to be very carefully…arranged. We arrange them in what we call "anatomical order" just as if the person was lying on the table, with his arm—or—with his or her arms extended. And then they have to be carefully cleaned, sometimes with just gentle running water to get rid of any adherent soil that might interfere with their inspection of the bones. And once that's done…then we begin our more detailed examination of the bones which takes—um—in a lot of careful measurements of the bones. Uh, for example, the bones of the arms and legs, we measure their length in millimeters and we have formulas that enable us to calculate the person's stature within a certain range of error. And other features on the bone tell us something about the person's age, gender and we also look—each bone—look at each bone very carefully, sometimes, often with a hand lens, to see if there are signs of old diseases and injuries that might be reflected in that person's medical history. And if we can find the medical records very often this helps in establishing that person's identification. And—um—so…and then finally, any evidence of trauma—gunshot wounds…in El Salvador and Guatemala very often we find machete cuts—uh—any evidence that can tell us something about how that person died…the final chapter—in their—what I call the "osteobiography". The "osteobiography" meaning the life history that's developed from the bones, from the evidence in the bone and it's usually pretty brief, but sometimes it can be very informative.