Novel collagen mapping method makes invisible ancient bones visible

"Our results will offer significant advances for the study of human evolution," says Talamo, co-author of the study and director of the Radiocarbon dating lab BRAVHO at the University of Bologna, "as we will be able to minimize the destruction of valuable bone material, which is under the protection and enhancement of European cultural heritage and thus allow us to contextualize the valuable object by providing an accurate calendar age."

The team has uncovered some of the rarest prehistoric bones, and many of these bones are extremely valuable. They are regarded as being a part of our cultural and historical heritage.

Bones can reveal a lot about the lifestyles of ancient populations, including their diet, sexual behavior, health, and migration patterns. Bones, however, cannot provide us with all the information we seek. The amount of collagen maintained in them limits their ability to convey information.

"We used imaging technology to quantify the presence of collagen in bone samples in a non-destructive way to select the most suitable samples (or sample regions) to be submitted to radiocarbon dating analysis," says Cristina Malegori, first author of the article and researcher at Genoa University Department of Pharmacy.

"Near-infrared hyperspectral imaging (HSI) was used along with a chemometric model to create chemical images of the distribution of collagen in ancient bones. This model quantifies the collagen at every pixel and thus provides a chemical mapping of collagen content," she added.

Collagen preservation

Analyzing all the bones available at one archaeological site for collagen preservation is highly challenging, expensive, and time-consuming; more significantly, it destroys priceless material. In actuality, as time passes, human fossils and/or bone artifacts become more and more uncommon and valuable.

"The near-infrared hyperspectral imaging camera (NIR-HSI) used in the present study is a line-scan (push-broom) system that acquires chemical images in which, for every pixel, a full spectrum in the 1,000–2,500 nm spectral range (near infrared) is recorded," says Giorgia Sciutto, co-author of the article and professor of environmental and cultural heritage chemistry at the University of Bologna.

Overall, this cutting-edge and insightful combination of NIR-HSI spectroscopy prescreening and the radiocarbon method offers, for the first time, in-depth knowledge about the presence of collagen in archaeological bones. It also lowers laboratory costs by only dating materials compatible with 14C and increases the number of archaeological bones that can be preserved and are thus available for future research.

Study abstract:

Many of the rarest prehistoric bones found by archaeologists are enormously precious and are considered to be part of our cultural and historical patrimony. Radiocarbon dating is a well-established technique that estimates the ages of bones by analysing the collagen still present. However, this method is destructive, and its use must be limited. In this study, we used imaging technology to quantify the presence of collagen in bone samples in a non-destructive way to select the most suitable samples (or sample regions) to be submitted to radiocarbon dating analysis. Near-infrared spectroscopy (NIR) that was connected to a camera with hyperspectral imaging (HSI) was used along with a chemometric model to create chemical images of the distribution of collagen in ancient bones. This model quantifies the collagen at every pixel and thus provides a chemical mapping of collagen content. Our results will offer significant advances for the study of human evolution as we will be able to minimise the destruction of valuable bone material, which is under the protection and enhancement of European cultural heritage and thus allow us to contextualise the valuable object by providing an accurate calendar age.