Copper alloy blades were discovered in much of Europe during the Chalcolithic, then during part of the Bronze Age. Despite the great diversity of exhumed sheets, studies on the function of these metallic artifacts are rare. A gap partially filled thanks to the microscopic analysis, by a team of archaeologists, of ten daggers discovered in northern Italy. The study, published in Scientific Reports on April 12, 2022, demonstrates a multifunctional use of these daggers, mainly in the slaughter of animals. According to Andrea Dolfini, an archaeologist at the University of Newcastle who participated in the study, “organic residue analysis is commonly applied to ceramic, stone and shell artifacts. Therefore, we modified the method to be able to apply it to copper alloys.”
An artifact associated with warriors
These daggers appeared simultaneously, in the 4thand millennium before our era, in much of Europe and on the Italian peninsula. Flint was gradually abandoned in favor of alloys of copper, with arsenic or tin. It is also the period of strong commercial activity, with exchanges of artifacts throughout Europe during the Bronze Age. The function of these daggers has been the subject of debate among archaeologists. Some interpreted them as symbolic accessories, or objects used for slaughter rituals. Frequent finds of daggers in warriors’ tombs have led archaeologists to believe they were non-functional insignia, symbols of male power. Also, the weakness of the copper alloy meant that these daggers could not be strong enough as close range weapons.
These artefacts were discovered between 2016 and 2017 at the Pragatto site (Italy), which is part of the Terramare system (name given to the specific archaeological culture of the Bronze Age), a prehistoric settlement site in the Po valley, occupied by – 1650 to -1200 BC. It is famous for its remains of square villages of 1 to 20 hectares, once established near rivers and surrounded by stockades. In addition, part of the village has traces of fire, which would have allowed the preservation of a certain number of elements until today: nine burned houses, a garbage dump, an animal enclosure and 150 mobile copper alloy rooms, including 55 daggers.
Organic residues on the blades
Examination of the 55 daggers shows that they were in prolonged use, with traces of repair and damage to the edges of the blade. Also, the very small size of some daggers requires regular sharpening until they are no longer usable. The researchers assumed the wear marks were caused by repeated contact with soft materials such as animal or plant tissue.
The 10 daggers that most carry these residues were selected to be analyzed in depth, thanks to microscopic observation and SEM/EDX analysis. They come in different lengths and most have the rivets attached to an organic wood handle. The observation under the scanning microscope thus showed organic residues accumulated along the blades and at the base of the handle, in addition to hydroxyapatite, a calcium phosphate formed on the blade by the remains of crushed bones. Traces of collagen, bone, muscle and tendon fibers were found, but also of plants, including starch from triticeaea family of cereals that includes wheat, barley, and rye.
These organic tissues were preserved thanks to metallic compounds that limit bacterial and enzymatic activity. The composition of the soil, rich in acids and tannins like peat bogs, also allowed better conservation of protein organic matter.
These recent analyzes show that copper alloy daggers were much more functional than that, especially in treating animal or plant carcasses. A use that fits the context of Pragatto where the creation was very popular. The effectiveness of these blades in cutting was confirmed in experiments with pig and deer remains, green wood and wheat, thanks to replicas in similar metal alloys. Furthermore, 7-10 days later, the appearance of orange/green oxidation caused by contact with meat was similar to the oxidation observed in Pragatto daggers.
But Andrea Dolfini does not exclude the first proposals. “It’s a safe bet that these metal daggers, and some flintlocks, were also used as weapons or as signifiers of male identity, perhaps related to clan status. In the Chalcolithic and early Bronze Age, they were often deposited in the graves of warriors, especially men.“While these results are significant, they remain speculative due to the rarity of this type of study of daggers from this era.”The method can be applied to any copper alloy from all over the world.continues the researcher. It can reveal a wide variety of organic residues of animal or plant origin. Further research may allow the isolation of other types of residues, eg fats, starches, hemoglobin from human or animal blood. But of course, we still don’t know how this line of research will develop in the future.“