Anthropologists at the University of Colorado Boulder have developed a new method of conducting important tests on ancient bones without destroying them. Using a portable near-infrared spectrometer, the team has found a way to measure the collagen content of preserved bones without the need to subject them to destructive sampling or chemical tests.
It's a credo in archaeology that excavation is destruction. A site can be dug up and the data recorded only once because the very act of digging up the past destroys most of what's there and removes the rest from the environment that has sealed them against contamination by later ages.
It's for that reason that archaeologists prefer not to excavate unless there is a compelling need and to, whenever possible, preserve as much as possible undug for future generations.
The same holds true for laboratory analysis. The ideal scientific instrument is something like a Star Trek tricorder – a machine that makes a whining sound as you just wave it over a sample and the data you seek is provided without damaging the subject. Unfortunately, many lab tests require taking samples that are subsequently destroyed in the quest for knowledge.
This isn't a problem in many other fields, but things like bone samples are rare, if not literally unique, and it's often a case of either preserving the sample or analyzing it, but not both. And for bone, this is particularly the case because of what it contains – collagen.
Collagen is an important component of bone. A mixture of various proteins, it acts as the structural matrix for growing bones and provides the normally hard and brittle inorganic bone tissue with strength and flexibility. For the archaeologist and anthropologist, it's also a treasure trove of information about how long ago a person or animal died, their state of health, what they ate, and many other factors.
In living bone, collagen accounts for about 30 percent, but this deteriorates over time until it's reduced to a trace after a few centuries. This means that extracting collagen from ancient bones often means sacrificing the sample for things like radiocarbon dating.
To avoid this, the CU Boulder team started experimenting with the near-infrared spectrometer as a way of detecting the distinct light signatures of collagen proteins. According to Matt Sponheimer, a professor of anthropology at CU Boulder, the spectrometer's handheld probe worked surprisingly well, returning results in seconds as to not only whether collagen was present, but in what estimated quantities.
In order to calibrate the instrument, the team used it on over 50 samples of ground-up bone and 44 pieces of whole bone ranging in age from 500 to 45,000 years with known concentrations of collagen. In each case, it came back with an approximately correct reading.
Because the spectrometer is about the size of a briefcase, it was also able to be tested in the field in Germany, where, along with scientists from the Max Planck Institute for Evolutionary Anthropology, the team examined human remains from the Dolní Věstonice site in the Czech Republic.
"The grad student on this project had only six vials of samples from human burials," says Christina Ryder, a graduate student in the Department of Anthropology at CU Boulder. "That was all she had, and that was all anyone was going to have for the foreseeable future."
Despite this, the spectrometer meant that they could minimize the amount of bone they had to sacrifice for radiocarbon dating. In addition, the hope is that the technique will one day also help in detecting the much less abundant DNA in ancient bone.
The research was published in Scientific Reports.
Source: University of Colorado Boulder