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Heli Illipe-Sootak, a Master’s student at the TU Institute of Mathematics and Natural Sciences, asks how to make 3000 years old earthenware pots speak in order to find out what people who lived in the Estonian territory so many years ago ate and drank.

Each earthenware pot excavated by an archaeologist carries more information than is visible at first sight. Chemical analysis helps to lift the veil of secrecy from Stone Age eating options and habits. Chemical analysis enables us to study different fat molecules present in the findings. This modern research branch has an exciting name: bio-molecular archaeology.

What do 3000 year-old earthenware pot fragments speak about?

Each year archaeologists excavate hundreds of earthenware pot fragments. All findings are dated - or almost all! It is then decided whether the object represents comb or cord ceramics or another prehistoric cultural epoch. Together with other findings, the living customs of that period are outlined. But there is more. Each fragment of ceramics includes much more information than visible at first sight.

Due to the development of analytical methods, it is really possible to make a lifeless piece ‘speak’; to learn about this I first went to the Archaeology Laboratory at Stockholm University in Sweden, where I was taught by the globally recognised specialist, Sven Isaksson.

What can be studied in bio-molecular archaeology?

Study objects can be all kinds of natural materials: carbohydrates, wood, paper, plant fibres and adhesives including proteins, such as skin, silk, animal and human hair. Of course, fats such as oils, ointments, fatty food, perfumes and waxes can also be studied!

Have these components really been preserved in their original form?

Unfortunately, they haven’t! As happens in nature, all chemical compounds tend to dissolve or turn into something else: animal fats hydrolyse, unsaturated fatty acids undergo auto-oxidation and archaeologists’ greasy hands contaminate samples. Nevertheless, the situation is not hopeless!

Certain molecules remain and these are used as biomarkers. Cholesterol, with its ugly name, is a marker of animal fat, ergosterol is a marker of fungus and stigmasterol is a marker of herbal fat. Tars and resins, and isoprenoid acid, characteristic of fish, also tell us much.

How do we discover what is hidden in one earthenware pot fragment?

Everything starts from taking a sample. A suitable fragment must be drilled, which can be done with a common tile drill. This is followed by US-extraction i.e. separation, centrifugation, etc., until a nice fatty layer remains in the bottom of the bottle. You could put it on bread. However, this is not recommended because substances used in the process are toxic: methanol and hexane. After that the sample goes to the machine.

Gas chromatograph mass spectrometer - What animal is that?

A gas chromatograph pulverizes the sample, in other words turns it into a gaseous form. A mass spectrometer determines what kind of molecules have passed through a thin tube and then creates a table of results – “peaks”, as the specialists say.

Does the machine give you the list of substances?

No it doesn’t and for that we need a person who would go through this “forest of peaks” in the table and find out whether interesting components exist in the sample.

What can be found out?

Earthenware pots were used for storing seal grease or fish, cattle products or even herbal food. I also wanted to know if people drank milk 3000 years ago. This can be determined if a sample would include triglycerides in a certain order. My sample didn´t. Therefore we have a reason to continue investigating!