Synthetic replicas jostle for analyzing bloodstains on prehistoric and ethnographic tools

An experimental study at IPHES shows that they can faithfully reproduce the morphology of red blood cells

Currently, dentistry, palaeontology, criminalistics and archaeology are some of the fields where they are applied

They could also be applicable to other organic residues such as muscle, skin or tendon, or the surface of other types of specimens, such as clinical samples or industrial pieces

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Some archaeological and ethnographic specimens are not available for direct examination using a scanning electron microscope because of methodological obstacles. For example, the piece is too large to fit in the chamber of such instrument, or it is a structure that cannot be moved from its place, like a ceremonial altar. There may also be legal troubles because the custodian or owner does not grant permission to take it out from the museum or private collection. In this context, synthetic replicas jostle for in many fields. Currently, dentistry, paleontology, criminalistics and archaeology are already some of the fields where they are applied.

At IPHES (Institut Català de Paleoecologia Humana i Evolució Social), synthetic replicas are used in different types of research (taphonomy, palaeoanthropology, prehistoric technology) for a long time. So far, in prehistoric technology, this type of replicas have been used for microscopic examination of traces of use, but its application to organic residues had not received the same interest. This situation may now change with the scientific contribution by Policarp Hortolà, biologist and researcher at IPHES. In an experimental study published in the journal Microscopy and Microanalysis, he shows that synthetic replicas can faithfully reproduce the morphology of red blood cells in bloodstains. Therefore, “they are feasible for identifying, via scanning electron microscope, bloodstains on archaeological and ethnographic objects”, he says.

“The most important advance is methodological, because it allows examining, under the microscope, replicas of organic residues instead of the originals”, this researcher says. It could also be applicable to organic residues different from blood (e.g. muscle, skin, tendon, etc.), as well as the surface of other types of specimens (e.g. clinical samples or industrial pieces) when, for any reason, the original is not available for microscopic study.

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Original (left) and synthetic replica (right) (© Microscopy Society of America)

To determine the viability of synthetic replicas, Policarp Hortolà carried out a pilot study with human bloodstains on stone, wood and shell, which are some of the organic materials used by prehistoric and etnohistorical societies for the manufacture of their objects.

The final objective was to evaluate the feasibility of using synthetic replicas for identifying bloodstains through the morphology of red blood cells. Broadly, if organic residues can be replicated without damaging valuable originals, then they could be studied microscopically without removing the original pieces from museums or private collections.

Silicone moulds and polyurethane replicas
To make the replicas, first silicone molds of bloodstained areas were made, from which polyurethane resin replicas were obtained. Subsequently, the original samples and their corresponding resin replicas were examined with a scanning electron microscope. Finally, the results of both types of samples were compared. “It should be noted that, in all the studied samples, the ability of the replicas to reproduce the morphology of red blood cells in the bloodstains was confirmed”, Policarp Hortolà remarks.
Reference

Hortolà, Policarp (2015). Evaluating the use of synthetic replicas for SEM identification of bloodstains (with emphasis on archaeological and ethnographic artifacts). Microscopy and Microanalysis 21(6), pp. 1504-1513.

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