Image: Credit: NTBScanpix, CC BY-SA 4.0., via Wikimedia Commons


Archaeologists have found what they say is the first solid scientific evidence suggesting that Vikings crossed the North Sea to Britain with dogs and horses, as Dr Tessi Loeffelmann explains


Profile: Dr Tessi Loeffelmann

Dr Tessi Loeffelmann is a bioarchaeologist with a background in human osteology and palaeopathology, predominantly conducting her research using isotope analyses.

She has previously worked as a field archaeologist and an osteoarchaeologist, but then decided to return to academia where she focused on cremated human and animal remains from the early medieval period.

She has just completed her co-tutelle PhD research at Durham University in the UK and Vrije Universiteit Brussel in Belgium, and is now a postdoctoral researcher working on a variety of projects.

The first solid evidence that Vikings brought dogs and horses to Britain has been found. Researchers from Durham University in the UK and Vrije Universiteit Brussel (VUB), Belgium, studied the cremated remains of people and animals from more than a thousand years ago, in Britain’s only known Viking cremation burial site.

Using strontium isotope ratios in bone fragments found at the Heath Wood site in Derbyshire, England, lead author of the study, Dr Tessi Loeffelmann, who is affiliated to both universities, tells Aether of the research conducted and the findings uncovered.


Image: Viking burial mound at Heath Wood being excavated. Credit: Credit: Julian Richards, University of York. (CC BY 2.0)

This research is part of my PhD project for which I used strontium isotope analysis to look at mobility in the past. Specifically, I studied cremated human and animal remains from early medieval cemeteries in Britain to assess whether the individuals moved location during their lifetime. My research is based on a new method which, for the first time, allows us to study cremation deposits isotopically. We know quite a lot about early medieval mobility through isotope studies (mostly strontium, oxygen, sulphur, and lead) but until now all of this research has only revolved around inhumation burials.

In archaeology, sudden appearances of things always ultimately trace back to the question of whether it was the movement of people, or the movement of ideas that caused it. In this article, I want to concentrate on the results from one of my case-study sites – the Viking cremation cemetery Heath Wood, near Repton, in Derbyshire. I am taking you back to the late 9th Century AD, when the Viking Great Army was in the process of conquering large parts of England.


How isotopes help us to understand mobility in the past 

The method itself is borrowed from geochemistry, where certain isotopes can be used to look at geochronology – the age of the rocks in the Earth’s crust, or meteorites. The study of mobility of past people involves predominantly strontium (Sr) and oxygen (O) isotopes which are measured in skeletal tissues like tooth enamel or bone. An isotope is basically an atom of a specific element, which differs in the number of its neutrons (and therefore its mass), but stays the same element, nonetheless.

For strontium, there are four naturally occurring isotopes: 84Sr, 86Sr, 87Sr, and 88Sr. One of these is radiogenic, meaning it is a decay product of rubidium 87 (87Rb). Over geological time, 87Sr increases independently of the original content of strontium in the bedrock, and this leads to the fact that generally, older rocks have higher amounts of 87Sr.

When we eat plants and drink water from a specific area, we incorporate the strontium from the environment into our skeletal tissues. So, in these terms, you truly are what/ where you eat! Bioarchaeologists use the ratio of 87Sr to 86Sr (expressed as 87Sr/ 86Sr) to compare the strontium of specific lithologies with that measured in tissues of human and animal remains. We expect people in the past to have been relatively reliant on locally produced foods and local water, and that helps us to determine if someone is likely to have lived in the area they were buried in.


Image: Fragment of a sampled cremated horse radius/ ulna from burial mound 50 at Heath Wood. Credit: Jeff Veitch, Durham University. (CC BY 2.0)

It also matters which type of skeletal tissue is used by the bioarchaeologists to measure strontium isotopes: tooth enamel forms during the childhood of a person and does not remodel throughout life. In that case, we know about their childhood mobility, and we can see whether they moved during adulthood if the 87Sr/ 86Sr does not match that of the area they were buried in.

There is an issue with using the rest of the skeleton for this sort of analysis, because once a skeleton has been under the soil for some time, the bone can take up strontium isotopes from the soil. This is called diagenesis and would cause the person to appear ‘local’ to the area that they were buried in, even if they were not.

The great thing about cremated remains is that the intense heat of the fire (this can easily reach up to and over 1,000°C) changes the mineral matrix of the bone in such a way that it does not exchange strontium isotopes with the soil. The 87Sr/ 86Sr we measure in the bone fragments reflects the 87Sr/ 86Sr of the food that the people ingested over a long period of time in adulthood – depending on which bone is used. Thick long bones such as that of the femur (thigh) reflect that of the last 20 or so years of life, while ribs reflect a much shorter timespan – maybe five to ten years. In that way, larger differences in 87Sr/86Sr between bones or teeth can show roughly when a person travelled in their lifetime.


Image: Clasp from the Viking warrior’s shield found during the original excavations in 1998-2000. The clasp was found in the same grave as the human and animal remains analysed during the latest research. Credit: Julian Richards, University of York. (CC BY 2.0)


Image: Decorated hilt guard from the Viking warrior’s sword. The sword was found in the same grave as the human and animal remains analysed during the latest research. Credit: Julian Richards, University of York. (CC BY 2.0)

People from the past


Bioarchaeology is a specific field in archaeology which focuses on the remains of humans – and to a certain extent animals. Our questions usually revolve around health, disease, the lifecycle, mobility, identity, and anything related to this, so the subject area itself is quite broad and encompasses different strands of research and a variation of methods. For example, I use isotope chemistry to extract information on mobility from cremated human and animal bone, from individuals who lived more than 1,100 years ago in Britain. I love this research, because it allows me to learn about specific people from the past whose remains we have found, but who we know nothing or very little about. It is an absolute privilege to work with human remains and I think we must recognise that while this sort of research allows us to learn a lot about health, disease, and social practices in the past, it requires a strong ethical backbone. Ultimately, we destroy small parts of a person, no matter how long ago they died. For me, this aspect of the work is crucial as it always forces me to reflect on what I do, why I do it, and what I stand to gain from it – is it worth it?


The Viking Great Army


In this vein, I count myself as incredibly privileged to have had the opportunity to work with the cremated remains from Heath Wood – the only known Viking cremation cemetery in the British Isles. Based on only this aspect it is already a ridiculously interesting site, but it is also related to the arrival of the Viking Great Army to Britain in AD 865. This was at a point in time when the Viking attacks on Britain changed in character; raiders from Scandinavia had troubled British shores for about a hundred years or so before AD 865, but during that time they mostly attacked specific sites and then left immediately. When the Army landed, their aim was to conquer land – they came, moved around the country, and overwintered. Ultimately, this resulted in the creation of the Danelaw, an area in eastern and northern England which fell under Scandinavian rule – a very interesting time in British history. The Heath Wood cemetery consists of 59 mounds which are clustered on top of a small hill near Repton, in Derbyshire. Nowadays, the mounds are overgrown with fern, but some are large enough to be made out in a clearing in a small forest.


Image: Cremated animal and human bone from the Heath Wood Viking cemetery. Credit: Julian Richards, University of York. (CC BY 2.0)

Only 20 of these mounds have ever been excavated, most of them before 1960. The issue with early excavations is that when cremated remains were encountered, they were not considered very useful and this meant that often, they were not kept in museum storage. The same is the case for Heath Wood, unfortunately – we do not have any remains from the early excavations there. The most recent excavation took place in the late 1990s under the direction of Julian Richards and Marcus Jecock and from this work, we thankfully have some cremated bone.

A popular misconception is that cremated remains are ashes – that’s not correct; when a body is cremated, all organics (soft tissues as well as the organic part of the bone matrix) are destroyed and what remains is the inorganic, mineral part of the bone. This will fragment, shrink, and warp – but in essence, it is still the skeleton. In modern crematoria, a cremulator is used to grind these fragments into powdered cremated bone, or ashes. In archaeology, we do not encounter this form, rather we are presented with heaps of fragmented bone and can therefore sometimes identify specific parts of the skeleton (although that is a speciality in its own right).

For the isotope analysis, I chose fully calcined (fully white) fragments from a horse, a dog, and a possible pig from amongst the remains in mound 50, as well as an adult and a non-adult human. For mound 56, I only sampled fragments from one adult human.

The fragments have to undergo a cleaning process; first, within an ultrasonic bath in ultrapure (distilled) water and light acid to remove any remaining organic material. That way, we know they are completely clean and we will only be measuring the strontium from inside the bone mineral. When the fragments are dry, they are ground into fine powder and about 15mg – a very small amount of sample – is weighed out for analysis. In most cases, we try to destroy as little bone as possible because of ethical considerations. The next stage involves column chemistry for which the sample is completely dissolved, the strontium is caught in a special resin and then released into clean beakers. The result is about 6ml of clear light acid which is evaporated overnight on a hot plate.


Image: Tiny spicule of strontium in a Teflon beaker. Credit Tessi Loeffelmann (CC BY 2.0)

The next morning when one checks the sample, there is usually only a tiny pin-prick-sized blob of strontium in the bottom of the beaker. To me, that is always a frightening point, especially when I do not see the blob right away. After some more chemistry, we can finally measure the sample in our mass spectrometer.

I also wanted to make sure I knew what 87Sr/ 86Sr to expect for people who were locals (or ate locally), so I sampled plants for the major lithologies in a 25km radius around the cemetery and measured them for 87Sr/ 86Sr in a very similar process as the one described above for bone. The results of this gave us a range, and any human or animal which fell into this range could be considered ‘consistent with the local environment’. Bioarchaeologists use this phrase frequently because it suggests that although the people seem local, they could also be from somewhere else with similar lithologies.

Very old lithologies


At Heath Wood, I expected that perhaps some of the humans would turn out to be non-locals, but to my absolute surprise, one human and all the animals returned with high 87Sr/ 86Sr ratios. They were indicative of very old lithologies, such as those that crop out in small areas of the highlands in Scotland and the Western Isles, and perhaps some rubidium (Rb) rich areas in Devon or Herefordshire. The issue with those areas in Britain for our interpretation was that they are spatially limited, in areas where we do not see any evidence of Viking activity at this point, or on islands and coastal sites where seawater would dominate the 87Sr/ 86Sr ratio (lower it so that the individuals might appear consistent with lots of areas in Britain).

In the context of the archaeology – that is the mound burials, the cremation site, and the Scandinavian-style grave goods – we therefore concluded that these animals most likely came from Scandinavia where there are large extents of these very old lithologies. The geological region is called the Fennoscandian or Baltic Shield and covers most of Norway and northern and central Sweden.

We can exclude Denmark for those individuals with the high 87Sr/ 86Sr ratios, because the lithologies here produce much lower ratios. For the two humans with the ‘local’ strontium values we cannot absolutely exclude Denmark or southwestern Sweden as a possible place of origin, but we will probably never be able to be sure about this. We know that the Viking Great Army was made up of smaller groups from different areas of Scandinavia, so the fact that the humans buried in the mounds have vastly different 87Sr/ 86Sr ratios is plausible. Alternatively, some archaeologists suggest that the burials may have been constructed by Scandinavian settlers who moved to Repton after the Great Army conquest of the area.


Importance in mythology


For me, the most interesting part was the fact that the horse, dog, and possible pig came from far away. They must have been transported on ships alongside people and these specific animals were likely important to someone. There is no other reason why they would have been taken along otherwise – Vikings knew that there were horses in Britain at the time. In fact, our main primary source of the time (Anglo-Saxon Chronicle) reports for AD 865 that the Viking Great Army took horses from the Anglo-Saxons living in eastern England once they landed.

Our isotope data shows that this was not the entire story – of course, it never is. When we consider written sources from the Scandinavian areas such as the Eddas and Sagas, the decision process involved in going through the hassle of bringing your own horse and dog along on a ship makes more sense; these writings emphasise the importance of specific animals in mythology and suggest that Scandinavians had a different perception of animals then we have today. This is also reflected in Scandinavian art at the time which is featured on many objects such as weapons or jewellery.

This research was the first isotopic study of its kind on early medieval cremated remains from Britain, because the method has only recently been shown to work by Christophe Snoeck (Vrije Universiteit Brussel) and colleagues. We have only now started to look into the mobility of cremating communities – and there are so many periods in the past where cremation was the main funerary rite. Until now, we were not able to explore this isotopically.

I cannot emphasise enough how exciting this development is for bioarchaeology! Of course, there are absolutely limitations with using only strontium isotopes as a proxy for mobility, but researchers here in Brussels and elsewhere are working on remedying this – they have been able to measure carbon and oxygen isotopes for the reconstruction of the cremation process, pyre technology, and are exploring the potential of other elements as well.

I am certain that the next few years will see a lot of developments in this area!

Image: Dr Tessi Loeffelmann. Credit: Tessi Loeffelmann (CC BY 2.0)


Dr Tessi Loeffelmann

Postdoctoral researcher

Vrije Universiteit Brussel, Belgium,

and Durham University, UK.


Twitter: @Tee_Loeffel