Archaeological finds

Lithics is a large find group consisting of various mineral (stone) objects, and it is the best and longest preserved archaeological material surviving over the millions of years. Stones have been used throughout prehistory for building various structures, ramparts, houses, hearths, stone-graves, field systems, etc. Considering stone-artefacts, the vast majority of lithics material is from the Stone Age (Paleolithic, Mesolithic, Neolithic, i.e. old, middle and new Stone Age respectively) and contain very different tools from hand– and other axes, adzes, various cutting blades, micro inserts (small lithic flakes inserted into organic material handle), burins and scrapers. In addition to actual artefacts, a large number of archaeological finds include production remains of stone objects such as knapping debris and cores. Furthermore, sometimes even ornaments (beads, pendants) or figurines can be made of stone. Besides the Stone Age material, lithics objects are found in later periods – mainly as various grinding stones and stands, whetstones, strike-a-light-stones, etc.

The most widely spread material used in Europe for stone objects in Stone Age is flint (consist of over 95% SiO₂, plus various other trace elements) found naturally in many places across the world. However, other siliceous rocks, like quartz and obsidian, but other materials such as porphyry and metatuf have been also used for making different tools [1]. Additionally, various stone materials unsuitable for lithic (cutting) tools due to their physical characteristics can be used for building and other purposes (lime-stone, sandstone). Very often locally available stone material has been used, but there are also several examples of long-distance trade of lithic objects covering thousands of kilometres [2].

The earliest evidence of pottery is from around the 20,000 – 12,000 cal BC from East Asia. It has been proposed that the innovation of pottery production spread from there towards west over several millennia [3] and pottery is indeed closely connected to hunter-gatherer societies [4]. In different regions of Europe the arrival of pottery varies in time from 7^th to 5^th millennium cal BC and different cultural names have been associated with the evidence of first pottery (e.g. Linear Band Ceramics in western Europe, Ertebølle in Scandinavia, Nemunas and Narva ware in the eastern Baltic etc.).

Since the arrival of ceramics in the second half of the Stone Age there has been a continuous use and development of various vessel types up to nowadays. The forms and shapes vary in time and range from large pointed base vessels to small bowls, large storage vessels to drinking cups. Vessels have been formed from clay coils (mostly Stone Age) or larger lumps of clay. For many millennia the pots have been hand-made, whilst from in later periods, usually Iron Age, also wheel-thrown pots emerge [5]. Locally available clay sources have been mostly used as a raw material, to which various binding material and debris (organic plant remains, shells, stone debris, crog etc. depending on the location and time period) were added to improve various physical properties incl. the heat-persistence of the vessels. In later historical periods the amount of imported pottery including e.g. stoneware increases.

There are two main strands of studying archaeological pottery. First is the analysis of technological aspects including the study of clay material and additives for provenance and production techniques. The other approach is to study the function and use of the vessels via analysing microscopic plant and animal remains preserved in pottery-related food-crust – charred food remains on the surface of the vessel [6-8]. 

Leather as the material has been widely used from the Stone Age onwards for clothing and footware, storage facilities (leather bottles) but also building material (coverage for huts) and toolmaking (attaching blades to handles). In later periods leather was also widely used for written records, e.g. as parchment. It can be presumed that the similar long-term use also applies to textiles, yet the direct evidence of early textile finds are scarce and often found as secondary marks (e.g. textile impressions on pottery). As with the leather, textiles can be used for numerous purposes, yet the most common is clothing and living conditions (decoration and warmth) as well as means for binding and attaching various objects (ropes and strings).

For leather items both wild and domesticated species were used and the selection of animal depended on the local availability (lack of domesticated species in earlier periods), purpose of use and objects made from it e.g. for parchment sheep/goat and cattle was usually preferred.  Textiles consist of fibres made from either animal products (wool, hair from sheep, goat) or plant fibres (see more in the section Textiles and dyes). In the northern hemisphere the most common plant fibres used for textile production is linen and hemp, but nettle can be used as well. Fibres are spun together forming long yarns woven into long strands. Textiles but also leather, can be coloured using dyes and pigments. Leather can be treated by tanning in order to improve its various chemical and physical characteristics such as weather-persistence and handling (softening).

Leather and textiles are all organic materials – leather is made up from animal collagen. Wool and hair mostly consist of protein called keratin, whilst plant fibres are made from cellulose (see more in the section Textiles and dyes). As such they are subject to rapid (on archaeological time scale) degradation and decomposition. This is the reason why these finds are rare and very special under archaeological conditions, for which usually humid and anaerobic conditions like peat and cess pits are the best preservatives [12].  Sometimes also other material such as copper (namely copper corrosion) buried in contact with textiles or leathers, may help to preserve these materials (see Fig. 4). For this reason, bronze spirals used in textiles decorations or bronze ornaments attached to textiles can be particularly useful for textile studies.

Archaeological bone material (osseous material) contains human as well as animal bones. Osseous material includes all the different parts of the skeleton including various bones and teeth.  The vast majority of bone finds are ecofacts, but bone material has been used for making tools (awls, harpoons), weapons (spear), toys and other artefacts (buttons).

Bones can be found in a whole variety of contexts and functions. They are remains of food consumption, various production practices, but also funerary practices (cemeteries). Depending on the function and relevant cultural practices they can appear as both burnt (fired food remains in hearths, cremations in cemeteries) and unburnt (rubbish pits, inhumation cemeteries) material, worked or deformed (polished, with gnawing and cut-marks).

Bone is made up from both mineral and organic components i.e. hydroxyapatite (a calcium phosphate mineral, 60-70%) and a protein called collagen (ca 27%).  

As partly organic material, the major concern with osseous material is its overall preservation, which depends strongly on the depositional environment (acidity, humidity, aridity etc.).  E.g. in the eastern Baltic and Scandinavia the bone material is generally well preserved, although acidic and arid sandy grounds (e.g. in Finland) are often devastating for bone preservation [13]. The other issue is the preservation of collagen. Visually the bone can be well preserved but its collagen can be degraded over time and such a material cannot be used for further analysis (e.g. stable isotope analysis or AMS dating). 

In addition to archaeological artefacts there are various amorphous residues attached to or found together with man-made objects or even ecofacts (dental calculus). These residues can be both organic or inorganic.

The major group of organic residues include archaeological food residues. These can be visible food remains, like food crusts, attached to the surface of the cooking or storage vessels, but also absorbed into the vessel’s (ceramic) matrix, or cooking environments (hearth stones, sediments) or textiles [14-17]. Additionally, there can be microscopic plant remains – carbohydrate rich starch grains, or silicate-based phytoliths or pollen grains preserved in the food-crusts or related vessels, human dental calculus, but also soaked into the cavities of stone artefacts like grinding stones or burins or cutting flakes [18-20]. In addition to food residues, there are various adhesives, lubricants, ointments, glues, medical mixtures etc. that can be found attached to various archaeological objects or within different containers [14]. Residues can be also analysed from ancient sediments or even coprolites [14,21].

The exact composition of residues varies considerably. In the case of organic residues, the major analyte class is lipids due to their better preservation and endurance to various depositional and environmental conditions. This applies to both food residues, but also adhesive, ointments, medicaments, but also sediments. 

The major concerns for residue analysis, especially for organic matter, is the (often extensive or even complete) degradation resulting in alteration of initial molecular profile or morphological features [14]. This may happen due to initial use and function of residues (cooking resulting in heating-related degradation of initial fatty content, or starch grain deformation), but also time and environment related degradation has to be considered, e.g. triacylglycerols decomposing into less diagnostic fatty acids, oxidation and hydrolysis changes the molecular profile of the initial substance. Furthermore, later contamination from find context’s environment and later storage and handling (e.g. moving pollen or starch grains, addition of artificial components like glues from the collection handling, modern hand-creams, soil pollution, plastic packaging) may influence the molecular profile of various residues as well [15,22-24]. Therefore the interpretation of the analytical results must be always conducted carefully considering the whole molecular profile and ideally combining different analytical techniques, but also taking into consideration all these different chemical reactions and alterations taking place in time.