Bring in the bones. And saw them into pieces.

8 July 2013 by Kerstin Hoppenhaus, posted in Human Evolution

On one of the cooler and rainier mornings this summer I was sitting on the terrace of the institute’s cafeteria with Jordi Rosell and Sahra Talamo. On the table: coffee in paper cups and a brown envelope stuffed thick with bubble wrap.

Jordi Rosell is a zooarcheologist from IPHES, the Catalan Institute for Human Paleoecology and Social Evolution in Tarragona, Spain, and he studies the interactions between ancient humans and animals. Between the bubblewrap he brought some animal bones from Teixoneres Cave, an excavation site about 60 km north of Barcelona.

Separating from their specimens is difficult for most researchers. Ancient human and animal remains are rare to come by, usually only with lots of hard work and quite a bit of good luck on top of it. So even for fairly common animals the numbers remain limited and every single bone or fragment is precious. But they are the basis of most of paleoanthropology and not all science can be done at the places where they were found. And since most scientists would never entrust them to any regular postal service, there is a steady stream of visitors who bring carefully sifted bones and teeth from all over the planet to the institute.

In the case of Jordi Rosell, his main interest is the exact age of a deer’s femur with distinct cutmarks on one end. Sahra Talamo is a specialist in radiocarbon dating. She will take care of the analyses.
In the caves that Jordi is investigating, they found animal bones with cutmarks, but no human remains, and it is unclear whether the creators of these cutmarks were modern humans or Neanderthals. Lithics and other finds are inconclusive, says Jordi. Precise dating could resolve the matter. But it is not easy.

A carbon dater measures the amount of radioactive 14C in relation to the „normal“ 12C. The ratio of 12C and 14C in the atmosphere is more or less stable, so all living organisms have a similar ratio in their tissue. But 14C decays, so when an organism dies and no longer refreshes its 14C stores by breathing and eating, the 14C to 12C   ratio begins to change and the carbon clock starts ticking.

Eventually, all the 14C is used up, so the time range for this method is limited, theoretically at around 60.000 years, but practically with the available detection methods at around 50.000 years. Which is a bit unfortunate for those who study human evolution, because this is exactly the time window where they believe that many interesting things between Neanderthals and modern humans have happened. So exact dating matters. To achieve this, one has to extract as much of the organic material from the bones as possible.

Which is the job of Lysann Rädisch, the technician in the radiocarbon lab.
Lysann usually works early. With every new batch, she lays out the specimens and carefully photographs, measures and labels them. This is important, because later they will be powders in test tubes and the labels will be the only way to track back their source.

Teixoneres site has been dated previously, about twenty years ago. But since then, the methods have developed a lot and Jordi and his colleagues no longer trust those dates. This is something I have heard in the other departments, too. Time ranges vary, but no matter if you talk to phoneticists, who tell me they don’t look at anything before the 1960s or only with extreme caution, or geneticists who won’t trust any data older than ten years – technological developments play a huge role in all these fields.

After documenting and labeling, Lysann begins to saw the precious bones into little pieces. Carefully and as preservative as possible, but without too much reverence for the piece’s ancient history. This is what she does. And she does it all the time.

She uses a dental turbine for sawing and has a considerable arsenal of drills and blades at her disposal. The turbine runs at low speeds, so one is spared the dentisty whine. But not the smell of cauterized tissue...

The bone fragments, 200 to 500 milligrams each, are then drowned in hydrochloric acid and in a number of different steps the collagen, the organic part of the bones, is isolated. The collagen will then be send to the AMS lab for the final results, and then Sahra will do the statistical analysis of the data. In the end, they will have a reliable date for the deer bone and the other pieces. Until then, however, they have to be patient (and occupy themselves with other questions), because to assign the bones their precise place in time will take months.

 

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