Seaweed-eating sheep and crop fertilisation trials on the Orkney Islands, Scotland

Magdalena Blanz, Vienna Institute for Archaeological Science (VIAS)

Seaweed consumption

In modern Europe, for most the idea of eating seaweed may seem strange. Outside of sushi, and memories of beach holidays where rotting algae spoiled the fun, most people today have no particular connection to seaweed. It may therefore come as a surprise that a fellow mammal, namely sheep (Ovis aries), can subsist nearly exclusively on seaweed. The most well-known breed of seaweed-eating sheep today are located on North Ronaldsay, the northernmost island of the Scottish Orkney archipelago. Elevated sheep δ13C values attributable to seaweed consumption were common in Neolithic Orkney as well, as the last two decades of archaeological research have shown (cf. Balasse et al. 2019, 2005 for a review).

Seaweed-eating sheep on North Ronaldsay. Picture by Jasmijn Sybenga.

Since the interpretation of archaeological data relies on modern comparative data to gain an understanding of what individual values mean in the archaeological context, analyses of modern material are required. Our study, recently published in the Journal of Archaeological Science, was conceived to collect further modern baseline δ13C and δ15N data for seaweed, terrestrial vegetation, and sheep bone collagen on the Orkney Islands. The results showed extremes of −10.7‰ for δ13C and +10.4‰ δ15N for modern seaweed-eating sheep bone collagen, and a δ13C average of −17.4 ± 1.4‰ for the analysed seaweeds (n = 20; mostly kelps). This modern dataset will help with future identification of seaweed-consumption, and allows an improved assessment in archaeological contexts of how much seaweed was likely consumed when the analysed bone formed.

Seaweed fertilisation

In addition to the consumption of seaweed, the use of seaweed as a fertiliser for terrestrial crops has also been suggested to influence consumer δ13C and δ15N values. To test this, we performed a field trial on Orkney where we fertilised bere barley (a six-row, hulled barley landrace) with seaweed. We followed traditional, historically attested practices with respect to the time and amount of fertilisation, but used a tractor for power-harrowing, sowing and rolling to reduce the still considerable amount of manual labour.

Fertilisation of 3 m × 3 m plots with seaweed (top left) and growth and harvest of the seaweed-fertilised bere barley. Pictures by Peter Martin, John Wishart and Magdalena Blanz.

Isotope ratio analysis showed significant elevation in δ15N values for seaweed-fertilised barley compared to barley from unfertilised control plots, but no significant difference in δ13C. This can be explained by the differing sources of carbon and nitrogen: Since barley takes up nitrogen from the soil (as nitrate, NO3, and ammonium, NH4+), the change in δ15N values upon fertilisation is due to the elevated δ15N values in the seaweed compared to the bioaccessible nitrogen in the unfertilised soil. In contrast, the lack of any major effects of seaweed fertilisation on δ13C is due to barley taking up most carbon by photosynthesis from the air (as carbon dioxide, CO2): Carbon stemming from the fertilisation at the roots has little likelihood of being taken up by the plant.

These results show that fertilisation of terrestrial crops with seaweed does not lead to these crops having more “marine” δ13C values, but that, similar to fertilisation with animal dung, δ15N values are affected by seaweed fertilisation. Further detail on the seaweed fertilisation field trial is available in Blanz et al., 2019 and Brown et al., 2020.

This research was undertaken as part of my PhD (2016-2020) at the Archaeology Institute, Orkney, supervised by Ingrid Mainland, Philippa Ascough, Mark Taggart and Jörg Feldmann. It was funded by the European Social Fund and Scottish Funding Council as part of Developing Scotland’s Workforce in the Scotland 2014–2020 European Structural and Investment Fund Programme.

Intra-individual Sequential Carbon and Oxygen Isotope Analyses of Neolithic Livestock for Assessing the Early Husbandry Strategies in the Southern Caucasus

Masato Hirose

Department of Earth and Environmental Sciences at Nagoya University

By sequential sampling and analyzing tooth enamel, we can read the seasonal variations in stable isotope ratios recorded in teeth. Seasonal variations in the stable carbon (δ13C) and oxygen (δ18O) isotopes can be used to infer what the individual consumed, where, and in what season. In other words, this method is suitable for studying the husbandry strategies from livestock remains. However, in the analysis of an isolated tooth, the term of the obtained variation would be short, and difficult to capture the feature of the variation. Analyzing two teeth per individual can provide long-term variation, although this requires the use of well-preserved archaeological materials.

Excavations at Göytepe (Photo: Dr. Seiji Kadowaki)

In our new study, we used this intra-individual sequential isotope analysis with M2 and M3 teeth per individual as far as possible to investigate early husbandry strategies in the southern Caucasus. We analyzed the mandibular tooth enamel of goats, sheep, and cattle (only isolated teeth) from the Neolithic settlements, Göytepe (ca. 5650–5460 cal BC) and Hacı Elamxanlı Tepe (ca. 5950–5800 cal BC) located in western Azerbaijan. As reference samples, we also analyzed modern goat and sheep individuals that are known to have grazed in the vicinity of the sites.

Map of the southern Caucasus, showing the location of Göytepe, Hacı Elamxanlı Tepe, and other main Neolithic sites belonging to the Shomutepe-Shulaveri culture. The locations of the obsidian sources are only those where the use of the obsidian was recognized in Göytepe materials (Nishiaki et al., 2019).

In this region, the first full-fledged Neolithic agro-pastoral economy called the Shomutepe-Shulaveri culture, emerged suddenly around 6000 cal BC. Despite their geographical closeness to each other, this is about 2000 to 3000 years later than the emergence of agro-pastoral practices in the Fertile Crescent. It is important to study the delay in this phenomenon in detail in order to understand the process of diffusion of agro-pastoral economy in human society. Therefore, in this study, we focused on how early agro-pastoral economy was practiced in this region under the peculiar environmental conditions colder in winter, adjacent to mountainous regions, that are uncommon in the Fertile Crescent. Livestock management regarding mobility and migration is a key aspect in understanding agro-pastoral societies. Therefore, we attempted to provide isotopic evidence indicative of early husbandry practices in the southern Caucasus.

Sequential stable carbon and oxygen isotope values of the Neolithic livestock from Göytepe.

The obtained data showed several different patterns that may be explained by different modes of husbandry practices:

  1. Some of the goats and sheep exhibit large amplitudes in δ13C and δ18O variations (see figure above: part a). This was interpreted as a lowland pasturing pattern because the modern goat and sheep showed the same pattern.
  2. A Neolithic goat and three Neolithic cattle samples exhibited relatively small amplitudes and/or inverse cyclical variation patterns (figure b and d). While these patterns may have been caused by multiple factors, such as drinking water and food/fodder, vertical transhumance has also been proposed to result in the similar isotope patterns (e.g., Henton et al., 2010; Tornero et al., 2016). If animals experience seasonal vertical transhumance between lowlands in winter and highlands in summer, it is expected that the δ13C fluctuation range reduces. In addition, the δ13C value of C4 plant feeders is presumed to decrease if they spend summer in highlands where C4 plants are less.
  3. Some individuals illustrated a pattern with a larger amplitude of δ18O seasonal variations but a smaller amplitude of δ13C variations (c). It is likely that some factor reduced the variation of δ13C. We proposed a possibility of the use of fodder (C3 plants) collected in a short term and given to livestock thus dampening the seasonal variation in δ13C.

The factors contributing to the patterns of isotopic variation presented in our study may not be limited to transhumance or the use of fodder but are consistent with such possibilities. To verify these hypotheses, other analytical methods, such as strontium isotope analysis, are required to specify pasturing places in different seasons on the basis of a local and regional isoscape. In any case, at least, these various sequential isotopic patterns suggest that a variety of livestock breeding strategies were already adopted by Neolithic inhabitants in the southern Caucasus. Thus, long-term sequential isotope data from plural teeth per individual would provide us more specific seasonal variation patterns.

This research derives from the Azerbaijani-Japanese Archaeological Mission directed by Prof. Yoshihiro Nishiaki (The University of Tokyo) and Dr. Farhad Guliyev (The National Academy of Science, Azerbaijan). The financial support for this study was provided by the JSPS KAKENHI (No. 17H04534), the MEXT KAKENHI (No. 16H06408 and 20H00026), and The Takanashi Foundation for Historical Science.

A consistent desire for animal proteins in the Bronze Age Xinjiang, China

Minghao Lin

Department of History, Shanghai Jiao Tong University, 200240 Shanghai, China

Location of Xinjiang (China)

The Xinjiang region is located in far northwestern China neighboring central Asia and Mongolian Steppe. Throughout antiquity it has been a nexus for exchange in ideas, technologies, livestock, or even populations. Although most of its land is covered by severe environments such as the Taklamakan Desert, diverse cultures have been recognised since the early Bronze Age. Near Eastern cultivars such as wheat and barley have been excavated and dated to by the beginning of the second millennium BC in this region. In spite of the appearance of wheat and barley at some sites, did the subsistence of ancient Xinjiang populations really rely on these novel C3 cultivars? The degree to which these Near Eastern cultivars contributed to human dietary intake and how these new food types shaped local subsistence strategies remains poorly understood.

The northern slope of the East Tian Shan Mountains in Balikun, Xinjiang (China). (Credit: Minghao Lin)

In this research, part of my Humboldt fellowship project hosted by Prof Cheryl Makarewicz at Kiel University, we conducted a regional scale meta-analyses of carbon and nitrogen isotope values measured from humans and animals including cattle, sheep/goats, and deer from sites dating from c. 2000 BC to AD 1000 within the Xinjiang region to examine the degree to which novel cultivars and animal proteins were incorporated into local subsistence system from the perspective of isotopic expression. We notice a narrow gap (1.7-2.7‰) in δ13C values but a wide space (4.5-6.5‰) in δ15N between humans and bovid samples. Meanwhile, we also record a consistent expression of high nitrogen isotope values visible in humans across time, indicating a persistent preference of the Xinjiang people for animal resources (e.g. meat, dairy proteins). This suggests novel cultivars of wheat and barley were not rapidly adopted in Xinjiang highlighting the food dispersal and acceptance across Eurasia during prehistory was a complex process.

Results of meta-analysis of stable carbon and nitrogen isotopic results from Xinjiang (China)
(Credit: Minghao Lin).

Chickens from Beyond the Grave

We’re continuing our series of posts this month with a piece by Elizabeth Farebrother, who is currently working towards her PhD at University College London investigating changing animal use in Western Asia during the Neolithic and Bronze Ages. Here, she shares her MSc research, which was part of the ongoing, multidisciplinary Chicken Project. Thanks to Liz and the Chicken Project Team for contributing!

An Integrated Faunal-centric approach to Stable Isotope Analysis at Wien-Csokorgasse Cemetery   

The integration of zooarchaeological research and stable isotope analysis can be incredibly insightful, allowing us to go beyond traditional research questions, and investigate, where relevant, socially-grounded questions from a scientific perspective. My introduction to the world of stable isotope research came through the AHRC-funded Chicken Project, and my MSc formed part of this ongoing collaborative research initiative to investigate human-fowl interaction.

Belle, a Nottingham local
Belle, a Nottingham local.

Wien-Csokorgasse – an Avar-period (6th-8th Century AD) cemetery site – is located in Vienna, Austria, and was excavated as a rescue operation in the 1970s. Zooarchaeologist Henriette Kroll carried out the faunal analysis for the site, and noted that the deposition of chickens within human burial contexts was both sexually, and hierarchically stratified; cocks were buried with males and hens were buried with females. Significantly, the length of each cockerel’s tarsometatarsus spur also corresponded with the inferred status of the human burial (Kroll, 2013).

Chicken bone is demineralised in order to extract the collagen for isotopic analysis.
Chicken bone is demineralised in order to extract the collagen for isotopic analysis.

To investigate the potential reasons for the inclusion of chickens within burials at Wien-Csokorgasse, carbon and nitrogen isotope ratios from the bone collagen of each bird were analysed and compared with the existing stable isotope study of the humans they were buried with (Herold, 2008). Prospective indicators for dietary differentiation, including biological sex, age, and cemetery chronology were explored. Perhaps the most striking result was the dietary correlation represented by δ15N values. This dietary signature would have built up in the bone collagen over differing life spans between human and chicken. To this end, the data suggest a significant overlapping period of time where each chicken may have lived alongside the human individual they were buried with.

Preliminary carbon and nitrogen isotope results for human burials and associated chickens.
Preliminary carbon and nitrogen isotope results for human burials and associated chickens.

The results of dietary stable isotope analysis were viewed through the lens of anthropological analogy, and interpretation included a diachronic survey of published and grey literature of contemporary bird iconography and bird diet in Europe. This meant that the wider social implications and behavioural patterns amongst the groups who used Wien-Csokorgasse were also considered in the study.


Thank you to all involved in the production of this MSc dissertation. This study would not have been possible without the help and expert guidance of the AHRC-funded Chicken Project, Dr Naomi Sykes, Dr Holly Miller, Dr Henriette Kroll, the NERC Isotope Geosciences Laboratory (BGS Keyworth) and the University of Nottingham.


Herold, M. (2008) ‘Sex Differences in Mortality in Lower Austria and Vienna in the Early Medieval Period’ Doctoral dissertation, University of Vienna.

Kroll, H. (2013) ‘Ihrer Hühner waren drei und ein stolzer Hahn dabei: Überlegungen zur Beigabe von Hühnern im awarischen Gräberfeld an der Wiener Csokorgasse.’ in von Carnap-Bornheim, C., Dörfler, W., Kirleis, W., Müller, J. and Müller, U. (eds.) Festschrift für Helmut Johannes Kroll. Offa 69/70.

Rethinking Mycenaean Economy

Stable isotope analysis in zooarchaeology is an exciting–and growing–research area, with the potential to inform and expand on  a multitude of questions about humanity in the past, present, and future.

Part of the mission of the working group and the purpose of our blog is to share ongoing research in this area with a wider audience. To that end, we’re launching a series of posts on current projects combining zooarchaeology and stable isotope analysis in innovative ways around the world and in all time periods. If you would like to contribute a post on your research, you can email suzanne_birch [at] Comments and questions on posts are welcomed and encouraged!

Our first post is by Gypsy Price, who is currently a PhD candidate in the Anthropology Department at the University of Florida. Her research uses stable isotope analysis to reveal differences in faunal economies in early complex societies, specifically Late Bronze Age (LBA) Mycenae, Greece. Thanks Gypsy!

Faunal Economy at Petsas House

View of Mycenae, with a plan of the citadel and location of Petsas House indicated by the red circle.
View of Mycenae, with a plan of the citadel and location of Petsas House indicated by the red circle.

Five years ago I got involved with the Petsas House Project, a domestic/industrial structure located downslope from the citadel of Mycenae dating to the Late Helladic III A2 (circa 1300 BC). Around the same time I had become increasingly captivated by Galaty and Parkinson’s “Rethinking Mycenaean Palaces” series which critically examined the extent, degree, and manner of economic authority engendered by Mycenaean palaces. Bottom line, the majority of our knowledge about Mycenaean economy is based on Linear B tablets, which are geographically, temporally, and topically restricted: they have only been recovered from a handful of palatial sites, and record only transactions of interest to palatial administration occurring in the months prior to their deposition. As a result, economic models have been constructed from the top down, resulting in a myopic sense of the movement of resources within the larger society and an artificial inflation of the influence of the palace.

Through isotopic survey, we can discern feeding groups that may be indicative of disparities in provisioning or foddering strategies, and patterns of importation of animals. It was here where I realized that the extremely well-preserved and extensive faunal assemblage at Petsas House could offer a unique, micro-scalar perspective on management and distribution of faunal resources in an extra-palatial industrial/domestic context with a palatial settlement. Furthermore, there was an available contemporaneous faunal assemblage which had been previously excavated from the Cult Center, an ideological complex located within the walls of the hilltop citadel.

Gypsy Price with Petsas House materials
Gypsy Price with Petsas House materials.

Thus, with the invaluable support of Dr. Kim Shelton (UC Berkeley) and my committee chair, Dr. John Krigbaum (University of Florida), my PhD research was born. My sample set includes four main species known to have been purposefully managed during the LBA: goat, sheep, cow, and pig/wild boar. I am using carbon (δ13C), nitrogen (δ15N), and oxygen (δ18O) ratios from bone collagen and bone apatite fractions to identify discrete inter- and intra-taxonomic feeding groups. Strontium (87Sr/86Sr) and oxygen (δ18O) isotope ratios from bone and serially sampled teeth are being used to identify season movement patterns and to look for evidence of extra-local individuals which may be indicative of importation. I am currently in the process of interpreting the structured variation in these data to elucidate some of the nuances of LBA Mycenaean faunal economy, allowing us to develop a “ground-truthed” model of management and distribution between disparate sectors of a single LBA Mycenaean palatial settlement for the first time.