Making the ‘invisible’ visible: A new technique for analyzing archaeological bones

It shows an innovative method developed by an Italian team that will revolutionize the field of archeology and radiocarbon dating and protect our cultural heritage. Researchers used it with surprising results on vestigial bones, making the “invisible” visible.

This important achievement was published in the journal Communication chemistry– The result of extensive research work coordinated by Professor Sahra Talamo, in which experts in the field of analytical chemistry from the University of Bologna and the University of Genoa collaborated.

The group has developed a new technique for analyzing archaeological bones, which allows for the first time to quantify and map with high resolution collagen, the invisible protein essential for making radiocarbon dates and thus obtaining new information about a human being. development.

“Our results will make a major advance in the study of human evolution,” says Talamo, co-author of the study and director of the BRAVHO radiocarbon dating laboratory at the University of Bologna, “since we will be able to reduce the destruction of valuable bones.” materials, which are subject to the protection and promotion of European cultural heritage, and thus allow us to contextualize the valuable object by providing an accurate calendar age.”

Many of the rarest prehistoric bones found by archaeologists are extremely precious and are considered part of our cultural and historical heritage. Bones can provide a great deal of information about the lives of ancient inhabitants: what they ate, their reproductive habits, their diseases, and the migrations they made. However, bones cannot give us all the information we desire. Their ability to transmit information is limited by the amount of collagen preserved in them.

In order to combine the need to preserve the artifacts as safe as possible with the need to perform radiocarbon analyses, the researchers therefore developed an innovative method that allows them, thanks to a near-infrared-coupled camera, to detect the average collagen content of the observed samples.

“We used imaging technology to non-destructively determine the presence of collagen in bone samples to select the most suitable samples (or sample regions) to submit for radiocarbon dating analysis,” says Christina Malligori, first author of the article. Researcher at the Department of Pharmacy, University of Genoa.

“Near-infrared hyperspectral imaging (HSI) was used in conjunction with a chemometric model to generate chemical images of collagen distribution in ancient bone. This model quantifies the amount of collagen in each pixel and thus provides chemical mapping of collagen content.”

It is very difficult, expensive and time consuming to analyze all the bones in a single archaeological site to preserve the collagen; And most importantly, it will lead to damage to valuable materials. In fact, human fossils and/or bone artifacts have become rarer and more valuable over time.

Because of the genetic alteration of collagen over time, large starting weights of Paleolithic bone (≥500 mg bone material) are necessary to extract sufficient collagen for mass spectrometry (AMS) 14C (minimum 1% yield). Furthermore, many of the most valuable archaeological bones are very small (and it is in this context that the technique described in this study really shines because it allows obtaining information about the location and collagen content still present in the bone sample.

“The near-infrared hyperspectral imaging camera (NIR-HSI) used in this study is a linear scanning (push sweeper) system that acquires, per pixel, full-spectrum chemical images in the 1000-2500 nm spectral band. The band (rays) were recorded near infrared), says Giorgia Cioto, co-author of the article and professor of chemistry of environmental and cultural heritage at the University of Bologna.

“NIR-HSI analysis is completely non-destructive. The time required to analyze a single bone sample is a few minutes, thus, the system can examine many samples in one day to find the ones suitable for analysis, saving time, money and unnecessary waste of valuable materials, which greatly reduces of time, costs and destruction of valuable specimens.”

This technique is expected to support the selection of samples to be submitted for radiocarbon analysis at many sites where previous attempts were not possible due to poor preservation.

“This new technique allows not only the selection of the best samples, but also the selection of the sampling point in the selected samples based on the expected amount of collagen,” says Paolo Oliveri, co-author of the paper and professor at the Department of Pharmacology at the University of Genoa.

“This method significantly reduces the number of destroyed samples for 14C analysis, and helps within the bone to avoid selecting regions that might present an insufficient amount of collagen for dating. This increases the preservation of precious archaeological material.”

“The potential of the method proposed in the current study lies in the type and amount of information provided by the predictive model, which addresses two fundamental and complementary questions for the characterization of bone collagen: how much and where,” says Christina Maggiore, first author of the article.

Thus, this experimental approach can provide quantitative information regarding the average collagen content present in the entire sample submitted for investigation. The scan can be performed not only in small, localized areas (as in single-point analysis), but can also consider the entire sample surface, thus producing a larger and more significant amount of data.

In addition, the combination of the HSI system with a PLS regression allowed, for the first time, on samples of ancient bone, not only to determine the total collagen content but also to determine its location at high spatial resolution (~30 μm), and to obtain quantitative chemical maps.

“In terms of radiocarbon dating, we can strategically sample bones of high heritage value. For example, knowing the exact amount of collagen concentrated in a specific area of ​​bone allows us to cut out just that portion,” Talamo says. “Moreover, when the prediction of collagen shows that the bones were poorly preserved, we can decide to perform a 14°C soft treatment to minimize the loss of collagen during extraction.”

Overall, this innovative and critical combination of NIR-HSI spectroscopy and radiocarbon method provides, for the first time, detailed information about the presence of collagen in archaeological bone, reducing laboratory costs by dating material suitable for only 14 °C and increasing the number of archaeological bones that It can be preserved and is therefore available for future research.