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Saturday, 24 August 2024

Using microfossils and pollen to determine the origin of a set of stocks in the collection of the Rijksmuseum, Amsterdam.

In 2019 a man donated a set of stocks to the Rijksmuseum in Amsterdam, which he claimed his  grandfather had acquired in the  1970s from a farm in Zeeland Province.  The museum put the stocks on display in 2021, as part of an exhibition about the Dutch colony in Brazil between 1630 and 1654. In 2023, the stocks were loaned to the United Nations in New York, where they formed part of an exhibition about slavery in Dutch colonies. However, during the New York exhibition, questions were raised as to whether the stocks had ever actually been to South America. A radiocarbon analysis suggested that the tree from which the stocks had been made was probably felled in about 1800, with the stocks probably being made in the first quarter of the nineteenth century. Furthermore, DNA testing established that the wood came from a lineage of Oak trees, which today is found growing in Europe between northern Spain in in the south and southern Scandinavia in the north. 

In a paper published in the journal Review of Palaeobotany and Palynology on 10 August 2024, Hans Piena of the Vrije Universiteit Amsterdam, the Dutch Open Air Museum, and the Royal Netherlands Historical Society, Bas van Geel of the University of Amsterdam, Tom Hakbijl of the Naturalis Biodiversity Center, Arie Kalis of Goethe University, Pim van der Knaap and Jacqueline van Leeuwen, also of the University of Amsterdam, and Kees Nooren of Utrecht University, describe the results of a study which looked at palynological evidence (preserved pollen and spores) to develop a forensic picture of the environment in which the stocks had been used.

Oak stocks in the collection of the Rijksmuseum in Amsterdam (Inv.nr. NG.2019–502). Measurements: 265 × 37.5 × 23 cm. Piena et al. (2024).

Sediment was extracted from holes and cracks in the stocks, and analysed for palynomorphs (pollen, algae and spores), and the surface of the stocks were analysed for surface wear and other traces of use.

The stocks comprise two oak beams resting on a pair of cross-braces. Each beam has nine semicircular openings, which correspond to similar openings on the other beam, with the pair making a hole. on the other beam. At one end of the beams is an iron hinge, at the other an obliquely worn padlock eye. The insides of the holes have been smoothed to a shiny surface, suggesting that the stocks were used frequently. The upper surface of the beams are also smooth, having apparently been rubbed frequently with sand; cracks and small holes on this surface were filled with sediment. There are also a large number of chopping and cutting marks on the upper surface, in places forming a chequerboard pattern. The underside shows no signs of similar wear or sanding, and is largely free of sediment. 

The two cross-braces yielded traces of attacks by Fungi and Woodworm, which are not seen on the beams, and are interpreted by Piena et al. as feet upon which the stocks sat. They were previously interpreted as side braces in the two slavery exhibitions, which would have led to the stocks being horizontal, holding prisoners seated on the floor. Under Piena et al.'s interpretation, the holes would have been vertical, forcing anyone  trapped in the stocks to stand.

The number '22' has been written on the upper surface of the stocks in blue chalk. The fact that this has not been rubbed of strongly suggests that it was written after the stocks ceased being used, possibly as part of an inventory process or auction sale. Before the twentieth century, chalk could be produced in few colours other than white, but blue is one of those colours, making it possible the number was written in the nineteenth century. 

The contents of a sediment-filled hole on the upper surface of the stocks were analysed for siliceous microfossils. This produced about 500 000 Diatoms per gram of sediment, with fifty different species identified. These were largely indicative of a mesotrophic freshwater environment, such as a slow-flowing stream or ditch.  This included the epiphytic Diatom Cocconeis placentula, which grows on the surface of aquatic Plants or Macroalgae. No marine or brackish water species were found. Phytoliths (opaline silica crystals which build up in the leaves of Plants as dissolved monosillicic acid taken up with groundwater and precipitated out as water is lost from the leaves via transpiration) associated with Grasses were found, but none associated with Palms. Also present in great numbers were the stomatocysts of Chrysophytes (Golden-brown Algae), which are also typical of freshwater environments, with about 460 000 stomatocysts per gram of sediment. Also present were samples of the freshwater Alga Spirogyra and pollen of the freshwater Plant Myriophyllum alterniflorum. All of these species are indicative of freshwater ecosystems, but otherwise fairly cosmopolitan, and can be found in tropical and temperate environments.

Samples of pollen and spores were extracted from eight different cracks and holes on the surface of the stocks, with five samples being extracted from one large hole. A total of 7106 individual specimens were found, including 142 taxa of spores and pollen, from 18 trees, 21 shrubs, 91 herbs, 5 Ferns, and 7 types of Fungi, Algae, and Moss. This high proportion of herb pollen is likely to be indicative of an open agricultural environment, probably with low nutrient levels. This contained only a small proportion of Chenopodiaceaetype and Plantago maritima-type pollen, making a salt marsh environment unlikely. Many of the pollen types are cosmopolitan in distribution, but others, including Armeria, Cistaceae, Erica arborea, Lavandula, Nerium oleander, Olea, Pinus pinaster, Quercus ilex, Urtica pilulifera, Eryngium tenue, Corrigiola telephiifolia, and Vitis vinifera, are typical of the Mediterranean region, while others, including Erica australis, Erica umbellata, Cistus albidus, Cistus populifolius, Cistus ladanifer, and Halimium halimifolium, are found only on the western Iberian Peninsula and in western North Africa. Notably, the pollen of Cedrus and Chamaerops, which are more-or-less ubiquitous in recent North African sediments, were absent. 

Many pollen samples from cereal species showed signs of heat-deformation, something which has previously been observed in samples from medieval cesspits, and which is thought to be associated with bread or porridge-making.

The stocks also show signs of Insect damage in places, and yielded some Insect samples. The Insect damage comes in two forms. The first of these is wide flat tunnelling in the cambium layer, which would have underlain the bark, and which is caused by the larvae of Buprestid or Cerambycid Beetles. The second form of damage is a series of small boreholes likely to have been caused by Anobium punctatum, a small boring Beetle commonly associated with wooden beams and objects in Europe, which favours humid indoor environments. The Insect remains found belong to Ptinus fur or Ptinus clavipesAdistemia watsoniLatridius minutus, and two unidentified members of the Corticariinae. Adistemia watsoni is a species native to South America, but which had spread to Europe by the nineteenth century. The Spider Beetles, Ptinus fur and Ptinus clavipes, are typically found in indoor settings, feeding on Human food or other Pland and Animal remains. A small Mite belonging to the family Macrochelidae was also found. This assemblage has been found in other archaeological settings, and is considered typical of an indoor environment with mouldy food, litter and/or hay, and possibly excrement. 

The underside of one of the cross-braces, which is worn and shows traces of Fungal and Woodworm attack. Piena et al. (2024).

Artefacts will typically begin to assemble traces and small microparticles of biological origin from the moment when they are made, enabling researchers to build up a life history of  objects of interest. Examination of the assemblage associated with the Rijksmuseum stocks showed no evidence of these ever having visited South America, despite earlier interpretations.

A prior DNA analysis of the wood suggests that the stocks were made from a tree which probably grew somewhere between northern Spain and southern Scandinavia, and it seems unlikely that it was transported for any great distance before being worked. This is because only wood with a high market value is typically shipped for any great distance, which effectively means wood with a straight grain and few knots. The wood from which the stocks are made has an irregular grain pattern and is somewhat knotty, which would generally only be used if the desired task required wood to be sourced locally. The stocks also show signs of having been worked using techniques typical for green wood usage, which again makes it highly unlikely that the wood was transported any distance before being used.

The style of the stocks, with holes on top forcing the prisoner(s) to stand is unusual, but is known to have been used widely on the Iberian Peninsula during the early nineteenth century, leading Piena et al. to conclude that the stocks are likely to be of Iberian origin.

The samples collected can be expected to have started to accumulate as soon as the stocks were  made, and to have continued to accumulate throughout their existence. Samples were taken from locations all over the stocks, and in one in one location, a hole, a succession of samples were taken from different depths. Despite this, other than samples from the lower side being dusty and samples from the upper side being sandy, there was remarkably little difference in the samples, suggesting that the stocks spent much of their lives in a single environment. 

The pollen samples collected from the stocks suggest that this environment was in western Iberia, while the DNA collected from the wood suggests that it grew no  further south than northern Iberia, which is at least a neighbouring region. 

The Insects collected from the stocks suggest a humid, indoor environment, while the presence of cereal pollen, and good preservation of the Diatoms and pollen suggest that the sediment in which they were preserved did was not exposed to moisture for long periods.

Based upon this evidence, Piena et al. consider two separate scenarios, which could account for the accumulation of microfossils seen on the stocks. 

It is possible that the entire assemblage is post-use, representing a time when the stocks had been abandoned in a slow-moving stream or ditch, in an open agricultural environment with poor soils and intensive Rye cultivation, an environment typical of the Iberian Peninsula in the nineteenth century. This scenario is supported by the good preservation of pollen and Diatoms, the type of sediment found, and the low number of Fungal spores, but contradicted by the presence of sediment only on the upper side of the stocks, not on the underside or in the cavities between the beams and cross-braces. 

Alternatively, the large amount of pollen from wild Grasses and Cereals, particularly Rye, makes it possible that the stocks were used in an indoor environment where Grass and Rye straw were used as litter. This is supported by the types of spores present, which are all from species associated with decaying Plant matter or Animal dung (including Human). This is consistent with the idea that the stocks were used in a humid, indoor environment. The presence of Fungal and Woodworm damage to the underside of the stocks would be consistent with them sitting on a moist floor covered with a litter of straw and hay, possibly in a stable or dungeon (with the latter being more likely, given the presumed purpose of the stocks). Thus the deformed Cereal pollen could have come from bread or porridge fed to prisoners, or their faeces if they were forced to produce this while trapped in the stocks, and the sand in the cracks on the upper surface would be consistent with frequent scrubbing of this surface. 

Historically, most stocks around the world were positioned on their sides, with prisoners thus able to lie down. The Rijksmuseum stocks, however, are of a far rarer design, which held the prisoner in an upright position, forcing them to stand upright. Such stocks were often ued in conjunction with a neck brace on a wall, so that prisoners could be held upright and restrained. This was once common in Spanish prisons, providing a likely origin for the stocks. Notably, such stocks were particularly common during the Peninsula War of 1807-1814 and the Spanish War of Independence of 1814-1823, both wars which were noted for numerous attocities. In other settings, however, stocks of this type were combined with a latrine bench with holes, with prisoners being held in a sitting position.

Por liberal?, 1814–1823, by Francisco de Goya y Lucientes, showing a  woman trapped in a horizontal type of stocks. Piena et al. (2024).

When obtained, little was known about the set of stocks present in the collection of the Rijksmuseum. They were identified as having (recently) come from Zeeland, and were considered appropriate for an exhibition about the Dutch colony in Brazil between 1630 and 1658. Subsequent investigations have suggested that they were most likely made in Europe around 1800, and never taken to South America. Subsequent investigations by Piena et al. have narrowed the likely point of origin to the western Iberian Peninsula, and suggest that they were used in a moist indoor environment, most likely a dungeon.

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