Report of Strontium and Stable Oxygen Isotope Results of Human Remains from the Roman Fort at Velsen, the Netherlands

October 24st 2016 Report of Strontium and Stable Oxygen Isotope Results of Human Remains from the Roman Fort at Velsen, The Netherlands Dr. Andrea L. Waters-Rist and drs. Jessica Palmer 1 Laboratory for Human Osteoarchaeology Faculty of Archaeology Leiden University The Netherlands Contact e-mail: [email protected] [email protected] Contact address: Van Steenis building Einsteinweg 2 2333CC Leiden The Netherlands 2 Introduction Strontium Isotopes Strontium isotope ratio (87Sr/86Sr) analysis is a method of reconstructing birthplace and geographical movement (e.g. migration, residential mobility) of archaeological human remains. The ratio of the isotopes strontium-87 to strontium-86 in geological deposits depends on the relative abundance of rubidium and strontium in the bedrock and on the age of the rocks, with factors such as the proximity to marine environments (Veizer, 1989) and atmospheric deposition (Miller et al. 1993) impacting local 87Sr/86Sr signatures (the 87Sr/86Sr of modern ocean water is 0.7092 (Viezer 1989)) (see Bentley 2006 for a review) (fig. 1). The 87Sr/86Sr ratio passes from the bedrock into the soil and groundwater and the bioavailable strontium enters the food chain. The food and water consumed by an individual while their bodily tissues are forming will match the bioavailable 87Sr/86Sr of the geological area in which they live. Due to this phenomenon the strontium isotope ratio in ones’ bones and teeth can be used to infer where a person was born and if and where they relocated during their life. Figure 1: Simplified sketch of the strontium cycle showing key processes that determine the strontium isotope composition of skeletal and dental tissues. From Willmes 2015: 25. 3 The hard outer layer of one’s tooth, the enamel, forms in infancy and childhood and thereafter does not undergo remodelling. The enamel of the permanent first molar begins formation around birth and is completed by the age of about three years; the enamel of the permanent second molar begins formation around three years and is completed by six to seven years of age; and finally, third molar enamel begins formation anywhere from eight to nine years being completed by eleven to twelve years of age (Reid and Dean 2006; derived from Northern European population data). Hence, dental enamel 87Sr/86Sr ratios tell us about where a person lived as a baby and a child. It must be kept in mind that our ability to match an individual’s 87Sr/86Sr value to a particular geological region(s) depends upon the existence of data detailing the biologically available isotope signatures of the region(s) in question. This has yet to be done for many geological areas within Europe. Fortunately however, biologically available strontium isotope ratios have been characterized for large geological areas in the following regions: The Netherlands (Kootker et al. 2016; for the Frisian area specifically see McManus et al. 2013), Belgium (Central and Southeast Belgium - Drouet et al. 2005), France (Willmes et al. 2014 and see the Isotopic Reconstruction of Human Migration database at http://80.69.77.150/), South- Central Europe (southern Germany, Austria, the Czech Republic, and Hungary – Price et al. 2001 and 2004), Germany (Central Germany - Knipper et al. 2016; Bavaria – Grupe et al.1997 and Schweissing and Grupe 2003; Southwest Germany - Oelze et al. 2012; southern Germany - Bentley and Knipper 2005), the Austrian-Italian Alps (Kutschera and Müller 2003), Portugal (Southcentral Portugal – Hillier et al. 2010, Southwestern Portugal - Waterman et al. 2014), Italy (southeastern Italy - Tafuri et al. 2016, the Veneto region of Northeastern Italy - Petrini et al. 2015), The Aegean (Nafpliolo 2011), and the Eastern Mediterranean (Cyprus, Lebanon, and Turkey – Rich et al. 2016). Often archaeologists will make use of a ‘local’ vs. ‘non-local’ distinction whereby the 87Sr/86Sr of the site and region in question is determined, with individuals who fall outside this range being classified as non-local. Seldom is it possible to determine exactly where they came from. Rather, it is more likely we can identify regions they did NOT come from, thus leaving a narrowed list of possibilities about where they might have come from. Thereafter, historical information, archaeological data (i.e. grave goods, mortuary treatment), osteological data (i.e. metric and non-metric dental and skeletal traits reflective of an individual’s biological ancestry), 4 and the results of other isotopic markers than can give clues about provenience (i.e. stable oxygen isotopes), can be used to make an argument about where a person most likely came from. Stable Oxygen Isotopes Stable oxygen isotope analysis of the ratio of oxygen-18 to oxygen-16 (18O/16O ratio), denoted as δ18O (δ=delta), is often used in combination with strontium isotope analyses to reconstruct mobility and migration. Whereas strontium isotopes are incorporated into the food chain via the soil and bedrock of a given environment, stable oxygen isotopes enter the food chain and drinking water supplies via rainfall (Bäckström 2016). The oxygen isotope ratios of rainfall in a particular area are determined by the climatic cline, with the most important factors being temperature, proximity to the coast, latitude, and altitude (Cuntz et al. 2002; Gat 1980; Yurtsever 1975). Stable oxygen isotopes are also incorporated into dental enamel, and analysis of enamel that formed at different ages will similarly reflect biologically distinct moments in an individual’s life. In Western European regions of similar latitude, temperature, altitude, and distance from the coast are the dominant factors determining the stable oxygen isotope values of rainwater (Kootker and Altena 2010). As clouds travel inland, the heavier 18O isotope is disproportionately lost first, leading to precipitation with comparatively high δ18O values. Thus, the farther away from the ocean a cloud travels, the more of the lighter 16O isotope it contains, and its precipitation will have comparatively low δ18O values. Altitude is another important factor as clouds will encounter colder air currents when they drift into higher elevations, and the heavier δ18O will rain down first in the thus temperature-induced condensation (Bowen & Wilkinson 2002; Kootker & Altena 2010; Laffoon et al. 2012). Lastly, latitude and the corresponding temperature cline need to be mentioned as a factor, because water vapour forms more easily in high temperature conditions (i.e. closer to the equator) and this vapour then condenses (in the form of precipitation) as the cloud encounters colder temperatures (i.e. areas further away from the equator), leading to the preferential deposition of the heavier δ18O isotopes in rain in warmer areas closer to the equator (Dansgaard 1964). As with strontium isotopes, stable oxygen isotopes cannot pinpoint the exact origin of an individual’s homeland or migratory locations, but rather add data to help narrow down the list of possibilities. Using stable oxygen and strontium isotope analyses together allows us to further reduce the list of possible provenance options. 5 Purpose and Hypotheses The purpose of this report is to present the strontium and stable oxygen isotope ratio results of three adult male individuals from the Roman site of Velsen I (also known as Flevum), The Netherlands (fig. 2), dated to the early decades after Christ (16-40 AD). The main individual in question is known as ‘the man in the well’ and is a tall (1.90m) young-adult (~20-30 years) male found in a well. Items found with him, including a dagger and sheath, suggest he was a member of the Roman military, possibly a soldier (Morel and Bosman 1989). Questions regarding the origin of this man have abounded for many years. Initial osteological investigations were conducted by Constandse-Westermann (1981; 1982) with additional newer analyses by Inskip (in preparation). The four main hypotheses regarding his origin can be presented as follows: (1) He was a Roman soldier who came to Velsen from a homeland in the Mediterranean region; (2) He was an auxiliary member of the Roman military who came to Velsen from a homeland in the area around the site of Velsen; (3) He was an auxiliary member of the Roman army who came to Velsen from a homeland in the approximate area that is modern-day Netherlands (including Frisia), and; (4) He was a member of the Roman military who came from a Roman outpost elsewhere in Europe. In regards to the second hypothesis it has been specifically proposed, on the basis of his tall stature, that ‘the man in the well’ may have come from ancient Frisia (e.g. Constandse- Westermann 1982), an area to the northeast of the Velsen fort (fig. 2). Two other adult male individuals found at Velsen I are also analyzed in order to provide context to the data from ‘the man in the well’. These men were likely also military personnel and strontium isotope data regarding their birthplace and childhood home may aid in the interpretation of the main individual’s homeland. 6 Figure 2: Map of The Netherlands showing the location of the Roman Fort of Velsen I (red dot), as well as other Dutch sites or locations mentioned in this report. The approximate location of the Frisian region in Roman times is outlined in green. Materials and Methods Teeth from the three skeletons were assessed for completeness and pathology. Small samples of enamel from intact molar crowns were obtained from areas free from pathology (i.e. avoiding caries, calculus, discoloration or pre- or post-mortem chips/cracks). For the ‘man in the well’, the three molars from the right mandible were sampled on the lingual surface (RM1, RM2 and RM3). For the second individual, (g2008/6 1989-Zn3) the first and third left maxillary molar were sampled on the lingual surface (LM1 and LM3).

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