The analyses done in the lab are first macroscopic (by examining and measuring with the naked eye) and microscopic (examining and measuring unseen properties using instruments).
In our case, the macroscopic analysis included recognising the date and provenance of pottery, glass, metal objects, coins and animal bones, and the microscopic included heavy mineral analysis, Organic residues analysis, stable isotopes and aDNA.
Pottery (Alessandra Molinari, Antinono Meo, Paola Orecchioni, at Rome)
Every pot sherd was recorded, measured and graded by the colour and texture of its clay mix and the dimensions and contours of its shape. Thanks to many years of work, Sicilian archaeologists can not only recognise the prehistoric, Greek and Roman coarse wares, fine wares and transport vessels (amphora) but the types of pottery that were used through the Medieval period that followed.
The experts in our project (the Rome team) filled many of the gaps in the pottery sequence and had particular success with the “dark” period of the 8th - 9th century when the island transitioned between Byzantine and Muslim control.
Glass (Francesca Colangeli, Nadine Schibille)
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Metal (Francesca Colangeli)
There was a large number of coins (Mammalato) but otherwise metalwork was quite rare. There was a model camel made of lead from Mazara and a touchstone for assessing the purity of precious metal from Castronovo.
Animal bones (Veronica Aniceti)
There were animal bones in profusion (analysed by Veronica Aniceti who did her PhD on the subject at Sheffield and York). The species were recognised from the bones and teeth left from farming and consumption at many sites, but especially at Mazara and Castronovo. cattle, pig, deer and sheep but varied through time.
Sheep were common throughout but pigs disappear from towns during Muslim rule and reappeared with the Normans. Farmers were enlarging their sheep through the centuries, eventually preferring them as wool producers in the Norman period.
Petrographic analysis (Claudio Capelli)
Claudio Capelli (University of Genova) identified the fragments of minerals included in the fabric of ceramic vessels and deduced where that mineral had most likely originated, using geological maps. In this way he could track amphora as they travelled across the Mediterranean from the place they were made to the place they were found.
Organic residue analysis (Ol Craig, Léa Drieu, Jasmine Lundy, BioArCh York)
Medieval pottery is porous so it can absorb small amounts of the liquids it contained – and characteristic chemicals (lipids) from these liquids are insoluble and can remain of centuries. The organic residues are extracted and separated and identified using modern test chemicals from fruits and vegetables that give the same signatures.
Comparing samples from the city of Palermo with some from the farm (Casale) at Castronovo, Jasmine found that the rural site had cooking pots containing dairy products and wine – which were absent from the city site. However, Léa discovered that amphorae made in Palermo when it was the Muslim capital were carrying wine to Christian sites widely spread over the Mediterranean. The Muslims may not have drunk wine but they knew how to sell it.
Stable isotope analysis (Michelle Alexander, Alice Ughi, BioArCh York, Efi Nikita (Cyprus Institute), Derek Hamilton (Scottish Universities Environmental Research Centre)
The isotopes we studied were those of carbon, nitrogen, oxygen and strontium. These get into human and animal bodies through food and their compounds remain in bones even after death. They are therefore known as 'stable' isotopes, and can be rediscovered by scientists and identified based on the different weights of their atoms.
The four isotopes tell us different things. The relative amount of Carbon14, the best known isotope, measures the time that elapsed since the organism died and gives us an approximate date of death. Carbon and Nitrogen isotopes provide a signature that characterises diet, since particular foods contain different relative amounts of these elements.
Varying amounts of Oxygen and Strontium isotopes are found in rocks from different locations. These get into freshwater pools from which people and animals drink and can remain in their teeth. If a person drinks water from one location when young and another before they die, this can be discovered by archaeological scientists through analysing layers within teeth. Oxygen/strontium signatures are therefore useful in establishing where people moved from and to during their lifetime.
Ancient DNA aDNA (Camilla Speller, Nathan Wales, Aurore Monnereau BioArCh)
As is well known, close relatives share similar DNA the molecules that you inherit from each of your parents which determine your individual characteristics. Mitochondrial DNA MtDNA preserved in the mitochondrial organelle which relates to the genetic inheritance from the mother, the Y chromosome relating to inheritance from the father (Y aDNA) and the whole genome extracted for the nucleus (nuclear aDNA) representing the best overall match of the individual to the current aDNA global map – the map showing the groups of similar DNA in the world today. The degrees of difference vary, so for the excavated individuals aDNA can show show where two people were closely related, the likely ancestry on the mother’s and father’s side and the best match to the modern population. It is seldom and exact equivalent so like most of archaeology it offers a “best fit” to where the individual came from.
Results from these last three types of analysis were most successfully applied to the samples taken from 26 cemeteries across Sicily - see Sicily's People for more details.