Gone Medieval - Vikings & Mice in the Azores

Episode Date: October 19, 2021

The Azores, an autonomous region of Portugal in the middle of the Atlantic, was said to be discovered in 1427 by Portuguese explorer Diogo de Silves. However, new studies of the land suggest the Portuguese may not have been the island's first inhabitants. The key to these studies? Mice. Similarities have been found between Azorean and northern European mice. In this episode, Cat is joined by Ecology and Evolutionary Biologist Dr. Jeremy Searle from Cornell University. We delve into this unexpected location of Viking occupancy, exploring Jeremy's research on the land and the mice who can tell us more about our complex history. What can mice tell us about the movement of people in the past? Hosted on Acast. See acast.com/privacy for more information.

From long-loss Viking ships and kings buried in unexpected places to tales of murder, power, faith, and the lives of ordinary people across medieval Europe and beyond. Join me, Matt Lewis, Dr. Eleanor Jarniger, and some of the world's leading historians as we bring history's most fascinating stories to life, only on history hit. With your subscription, you'll unlock hundreds of hours of exclusive documentaries

with a brand-new release every week exploring everything from the ancient world. to World War II. Just visit historyhit.com forward slash subscribe. Hello, welcome to Gone Medieval from History Hit. I'm Dr. Kat Jarman and I'm delighted to have you joining me today. Now, it might not surprise you too much that we're going to be talking about the Vikings again. And as you probably all know, the Vikings are known for being intrepid explorers and the journeys are pretty well documented both through historical sources and archaeological evidence. But now an increasing number of studies suggest they may have trouble

to other and rather unexpected locations, such as the Azores, an archipelago in the middle of the Atlantic. And some of this evidence actually comes from some rather unexpected sources. To tell me more about this today, I've invited an evolutionary biologist, Professor Jeremy Seale from Cornell University. Thank you so much for joining me, Jeremy. It's great to be here. Thanks very much. Now I'm going to get on to a bit later on why we have a biologist talking about this today. But Jeremy, so you've been working in this area for a little while. I was hoping that maybe just to introduce our listeners a little bit to the location, it might not be that familiar to everyone.

Could you start with a bit of backgrounds of the Azores and their islands and their history, like actually where they are and when we think they were first settled originally? Yes, I'm very happy to do that. So the Azores, as you said, are an archipelago. of a number of islands in the middle of the North Atlantic. And in terms of geography, they're on really at the boundary of some geological plates that are pulling away from each other. And they're volcanic islands that have formed there.

And some of the islands are pulling away towards America and some of the islands are actually pulling towards Europe. Now, they're very remote. And the sort of history books say, that they were discovered by the Portuguese in 1427. And from that moment onwards, they were visited by Portuguese and settled by Portuguese. The islands have overwhelmingly had a Portuguese history

since that 1427 date. By being in this location, in the middle of the North Atlantic, they've obviously also had visits from other mariners who are travelling through the Atlantic. But in terms of settlement history, they are overwhelming or completely Portuguese. And is there, or has there traditionally, before we go on to the new evidence,

has there traditionally been any evidence that anybody was there when the Portuguese arrived? Or is it thought to have been a sort of empty island? Well, as far as the history books go, traditional history books, it's always been said that the first sailors found pristine islands and that they truly did discover the islands. But of course, we're talking about the age of exploration,

and the Portuguese and Spanish were preeminent in that, and there was a lot of rivalry. And not necessarily the absolute truth was said at all times by people who discovered particular areas or people who got to those areas and they might not have wanted to know if there was something else, some evidence of other people there. But anyway, according to the written record, it was pristine environment.

And so how far are we from mainland Europe here in sort of sailing steps? Are we talking a really quite significant sailing distance? Well, it's essentially halfway across Atlantic. So it is a substantial distance. It's not something you can see from the coast of North Africa, the coast of Portugal. And going on to your research then, you first published a study back in 2015

that suggested a possible link between the Vikings and this island group. And in your research, you study evolutionary biology and especially the development of small mammals, particularly mice. Now, I just have to start off by saying, how can that tell us about movements of people in the past?

It is a very strange sounding thing, but the rationale goes as follows. So house mice are what are called commensals. That means that almost their entire distribution is dependent on humans. They exploit humans. They use our foodstuffs. They particularly live in places that livestock live in and feed on the food of the livestock. And so they kind of, they're absolutely associated with humans. And basically, wherever humans go, they're very likely to take mice with them.

And this is particularly the case for ships, you know, carrying food staff or ships carrying livestock, there will be mice with them. And so basically, obviously, we know which humans went to particular places because we know the identity of those humans, they came from particular places and went to those new areas, whether it's an oceanic island or whatever. But you can say the same for the mice. The mice obviously had to come from some source area and were taken to whatever destination you're interested in. So if we're thinking of the Azores, if humans came with mice to the Azores and those mice thereafter landed on the island and colonized the island because the humans had accidentally taken them.

Obviously, humans are not deliberately taking mice. These are passive travellers that come with the humans. Then those mice have a history. They came from some particular place. And one of the things that we and others have established is that in, you know, one of the substantial areas of distribution, of house mice is Western Europe and the Near East. And in different parts of that distribution, you find that mice have a different genetic signature. And we're particularly used a particular region of the genome known as the mitochondrial DNA. And this is a highly genetically variable

region. And it's for that reason that different parts of the distribution of the house mouse have a different characteristic. And so what this means is if mice came to the Azores, say from Portugal, we can genetically type the current mice that we find on the Azores. And if they have the genetic signature of Portuguese mice, we can make that connection that the mice came from Portugal. Those particular mice that we are looking at are descendants of mice. that arrived on the islands and had an original home in Portugal. So in this way, we can use mice as what I like to call living artifacts. So we're very used to, you know, your listeners interested in history are very used to

historical artifacts, which might be pieces of pottery, which are telling you that a, say, a particular group of humans that came from one particular area, went to another area, And you can identify that by the type of pottery that they leave in the area they visit. In a similar way, house mice that come from one particular area, in the destination that you're looking at, you can tell from their genetics where they came from. And so the artifact, in this case, the living artifact, the house mouse, is giving you information on source areas. And the nice thing about living artifacts is that you are making this designation on the basis of DNA. And DNA is incredibly information rich, really information rich.

You can work out things to do with the history of populations over time and so on from the DNA of the current population. So in no way is it a replacement for normal historical artifacts, but it's a useful additional tool to the toolkit of historians to be able to make use of these living artefacts. I like that. I like the idea of living artefacts as a brilliant parallel there. So tell me then about this study that you've been working on. What did you look at and what were your results of it?

So we were interested in the mice of the Azores Archipel. and we genetically type mice from all the islands on the archipelago and our strong expectation was that the mice that we found on the archipelago would have come from Portugal either Portugal or another archipelago which is closer to Portugal and that's the Madeira archipelago which we knew historically was something of a stoffing off point for both to the Azores. And we know that the mice from Portugal and Spain have a particular genetic signature, which is different from other parts of Europe. So we're basically testing that hypothesis

that the mice had that genetic signature, which indicated either that they came from the Madeira archipelago or from Portugal or Spain. So were you actually finding what you were expecting then in your results? Well, so we looked at these islands and indeed a number of the islands did show exactly what we expected. They showed a signature of coming from either Madeira or Spain and Portugal. But we had an additional really unexpected finding and that was that some of the islands, in fact, three of the islands had a signature for northern Europe. And this was a particular a genetic lineage of house mouse that we have found was really closely associated with the Norwegian Vikings or the Norse. And this association is really quite astonishing because, for instance,

in the British Isles, we find this lineage in house mice that are found in the very north of mainland Scotland, Cathness and places like that, on Orkney, on Shetland, on the Hebrides, on the Isle of Man and on Ireland, and this is the realm, the area of action, if you like, of the Norse. While other parts of Britain, the mice have a different genetic signature. And we also find this same Norse lineage along the coast of Norway and also Iceland. And we also find them on Greenland and Iceland from archaeological specimens that date to Norse Viking times. So we've got this really close association between a particular lineage of the house mouse and the Norwegian Vikings. We found this lineage on several of the islands in the Azores,

and this was really very surprising to us because we didn't see why there should be this association with the Azores and this Norwegian Viking lineage of housemouse. So in our 20, 15 paper we made the suggestion that this could have indicated a visitation of the Azores by the Norwegian Vikings and that there may not be at that time there was no material artefacts to indicate that association but you know our living artifacts the mice were indicating that potential association and as I say we view our mice as being something to help historians to think about alternative possibilities to what they may have thought of up to them. Yeah, and of course, with this then, presumably all you really need is for somebody to come there with

a ship with some mice on board and just stay on land for enough time for those mice to go on land and presumably just for enough mice to sort of have a new population that can survive. And that's sort of only really needs a very brief visit, doesn't it? Absolutely, and you're quite right about that. And the thing about oceanic islands, and this is where I'm going to be a little bit of a biologist, is that there aren't any other land mammals. And so the mice don't have any competitors, and they actually do extremely well on these oceanic islands. So if they can get a foothold, then they're very likely to survive to the current day.

Hi, I'm Professor Susanne Lipscomb, and in my podcast, not just the Tudors, we talk about everything, from sex to spying, wardrobes to witch trials. Not in other words, just the Tudors, but most definitely also the Tudors. Subscribe from History Hit wherever you get your podcasts. So the other thing I suppose that somebody can question about this is that you're looking at a modern population and you did mention that you've got some of these genetic lineages in archaeological samples as well. But from these islands, you don't have any specific dating evidence to you really. So there's no clear indication in your data to say when this happened, when they arrive. Is that right? No, there isn't any direct indication, but perhaps I can, I suppose to expand on this,

maybe I can talk about our findings from Madeira because they're really pertinent to this. Yeah, absolutely. Please too. Yeah. So really before we did this study on the house mice on the Azores, we've done a previous study on the Madeira archipelago and this is where we found really extraordinary data. Because what we found there, again, we had a really strong expectation that the mice on Madeira came from Portugal. And in fact, I and my colleagues only did this study because we just felt we wanted to just confirm that and move on.

It wasn't the main aspect of the study. But when we looked at the genetics of the mice on Madeira, we found that none of the mice that we looked at had any similarity to the genetic signature of mice from Portugal. They were just two completely different populations. And this was just utterly astonishing because Madeira had been discovered, according to the history books, by Portugal in 1419. And again, it had been all the settlement had been from Portugal. you know, the association was just astonishingly close with Portugal. So why were there no mice on Madeira that had some sort of association with Portugal?

We continued the study and studied more mice. In total, we looked at 122 mice from 20 locations on Madeira, and 121 of those mice had no association with portals. We did find one mouse that had an association with Portugal. And in Portugal we looked at 76 mice from 14 locations and none of those had a Madeira signature. So it's just like two different populations. But then the even more astonishing thing, when you looked at the genetics of the Madeira population, it was as if we had taken a cookie cutter in Denmark and taken mice from denmark.

from Denmark and taken a chunk of Denmark with the mice on it and plonked it in the Atlantic ocean and called it Madeira, the mice looked as if they were just Danish mice. And so, you know, we felt there was a really strong, strong indication that those mice hadn't come from Portugal, but they had come from Denmark from the area where the Danish Vikings were. And the, The only reason for that to happen as far as we could think was that the Danish Vikings had visited the island before the Portuguese and dropped their mice off. And that's all the mice, current mice, descend from those. And the interesting thing is the particular DNA marker we're looking at is maternally inherited mitochondrial DNA. And what seems to be happening is that the first colonizing mice, unless they go extinct, their descendants will carry on in the population and won't be replaced by subsequent mice.

It seems difficult for new incoming female mice to displace original female mice. So what this means is our mice is actually giving us a signal of the first colonists. And so that Madeira study really showed us that mice may be a really useful tool to archaeologists because we can say something from studying this mitochondrial DNA, which is telling us about first colonization of these islands by mice, which is telling us potentially about first colonizations by people, taking the view that people with ships are always going to have mice with them. That's really quite staggering.

And does this mean them, those Danish mice are different from the Norwegian mice. I was talking about different lineages. So actually, you could be talking about different events, different groups going there. Yeah, absolutely. So we feel pretty confident that the Danish Vikings did visit Madeira and that they drop their mice off there. And there is subsequent to our study, study of some mouse remains on the island of Madeira that were radio carbon dated to Viking Age. So that was, we felt pretty strong evidence that the mice, well very strong evidence that the mice got there before the Portuguese

and basically it can't have been the Portuguese that first discovered that island because the only way the mice could have got there was with people. So we have this close linkage, if you like, a well-substantiated linkage of the Danish Vikings and Madeira. We do see evidence of that Danish Viking lineage on the Azores. But the expectation there is where we see islands that have that type of mouse. They've come from Madeira, you know, rather than directly from Denmark. I mean, that's by far the simplest explanation. We know that with the colonization of the Azores,

there was movement from Madeira. So that was totally expected. So our finding on the Azores of mice, which are the Madeiraan lineage, in other words, the Danish Viking lineage, and mice with a genetic signature similar to Spain and Portugal, is exactly what was expected from history. What was unexpected is the finding on three islands of mice that are of the type that are associated with Norwegian Vikings.

And because of this finding on Madeira, the house mice, the mitochondrial DNA of current house mice is telling you something about first colonists. That made us very suspicious that Norwegian Vikings might well have stopped off in the Azores and left their mice. with them and that we're seeing that as a signal. At the time we wrote our paper in 2015, there was no archaeological evidence that we knew of for that. But, you know, that was our suggestion and something that we were hoping that archaeologists would bear in mind if they found something in the future. And that's what's happened with this new paper, I guess. Yeah, so let's move on to that then. So this is a new study that's just come out by a Portuguese team. So I know this isn't part of your own research. But this seems to

to back up this early settlement of the Azores. Can you just briefly explain what that study has shown? So what that study did, I mean, it was completely different from our work and much more typical archaeology. So what they were looking at was environmental signatures of human disturbance and indications of presence of humans. And what they showed from 800 AD onwards, there was indication of human settlement. and this was in several forms. There was charcoal particles. There was fecal sterols that they could link to livestock. And there was indications of reduction in forest, according to pollen records.

So this was demonstrated through coring of sediments in lakes on the Azores. And what was interesting in their study is that they demonstrated a continuous indication of human activity from around 800 AD up towards the time of colonisation by the Portuguese. So that's an interesting thing, given particularly as this sort of indication by the first Portuguese discoverers in quotes, that it was, the islands were pristine. Yes, that's pretty strong evidence. I suppose that somebody was there, even if that was perhaps so temporary at times that maybe they didn't leave anything very significant for archaeologists to find in what sort of a traditional way, which I think is really good.

And do you then, is your feeling that these two studies are showing the same thing, that we've got these Scandinavian or Viking settlers? Or do you think there could be other people from other parts of the world? Well, the team who carried out this archaeological work, they obviously knew about our work and they excited it. and they felt that further evidence of the settlers being Norwegian Vikings were that the prevailing winds to the Azores were from that direction from Northern Europe. And the dating also fits, of course, incredibly well with Norwegian Vikings 800 AD. So, you know, those pieces of evidence, and we know that Vikings were incredible mariners,

And indeed, there was a study of medieval maps by somebody called Kelly in 1979, and he already suggested an association of Norwegian Vikings and the Azores based on what he was reading in Scandinavian texts and the maps and the names on those maps. So there were a number of pieces of evidence there that are all pointing in the same direction. And the mice, as I say, are finding. on Madeira just so astonished, you know, I can't not underline how astonishing these findings are, that on basis of the DNA of the house mice in the islands of Madeira, there is barely any indication of Portuguese presence, you know, human presence,

which is just ridiculous because there's been so much Portuguese presence. So I think that we really should not brush a, away likely these mice of a genetic lineage that is associated with Norse Vikings. I would say that that is a piece of evidence that you should view strongly in the same way as you view various bits of archaeological evidence as being strong. So it's not to say it isn't disprovable, but it's something we should view strongly. So, you know, I have not seen evidence of other peoples going to the Azores, which is as strong as these three or four elements which all point to the Norwegian Vikings.

I think it's a very good point that we do absolutely need to take this into account and take it very seriously. And I think we need to also be careful not to rely too much on those written records and the places that we sort of feel we know the Vikings travel to, but be open to these different locations. And I think the point that we were talking about earlier on that you actually really don't need a very long-lived settlement at all. you don't need people settling, building houses. This could be a matter of, you know, weeks or days, just stopping off points, which makes perfect sense

because we know they were journeying in these areas. So, yeah, I have to say, originally, in 2015, when this came out, one of the people that thought, really? But the more you look into it, and the more I think you take those points into account, it does seem pretty convincing. I mean, what do you think we might need? What would you like to see,

what more as such would you like to do to see if you can back it up any further? Well, obviously it would be absolutely fantastic if some mouse remains could be found that were contemporary with the Vikings. And in terms of Madeira, you know, I knew that there had been some what might be called sub-fossil remains of house mice. And I didn't know where they were or who potentially could study them. but I was delighted when I saw the publication that had done this carbon dating on those sub-fossil remains. It would be wonderful if people could always be careful to, you know, now that we can be clued up that there were humans there and looking for places where those humans live,

and maybe, you know, the sieving that is associated with, that maybe some house mouse remains may come up and those should definitely be very carefully looked after and studied because not only can those be radiocarbon data they could potentially have their DNA looked at as well. A Viking scholar once said to me, you know, and this was in relation to the findings on Madeira and he and others had worked really hard to try and find some sort of mention of a place that was similar to Madeira in the sagas and they hadn't managed to find something and that was obviously disappointing we would love to have that sort of documentary evidence and maybe more work from scholars to see if they can find that would be fantastic

but one thing he said to me that really resonated about Vikings was that they were amazing mariners and one respect they were amazing mariners is that they quite often got blown off course or got to the wrong place but they were always very good at finding their way back. And they, I suppose their sphere of influence, when you think of all of potential places they may have visited, maybe rather larger than the sphere that we know about, the islands that we know about that were written about in the sagas. And they just might have just got blown off course or went on some speculative trip and just came back. But they were just such good mariners that they wouldn't have been lost with that sort of side trip. And I love the way they used ravens to

look for land and things like that. I mean, they were just astonishing mariners. And they carried lots of stuff with them and so it's not surprising that we find this great link really nice linkage between house mice and vikings that the vikings were great mariners went to all sorts of places they carried livestock with them they carried lots of food items with them undoubtedly would have carried mice with them and so they are a really kind of model system for you know using vines as a proxy for human history. Yeah, I completely agree. And I think this is a really exciting field of research.

And hopefully we can fill in some of those gaps in places that we didn't know about. So, yeah, keep up the good work. And I think I need to plan to move from my field, Muddy Field in Derbyshire, to the Azores for my fieldwork. And I'll try to find you some of my splines in the future. Okay, that'll be great. So that's, I think this is such a brilliant and exciting area to study. so hopefully we'll get some more evidence in the future. Jeremy, thank you so much for joining me

and explaining this to our listeners today. It's been wonderful to talk to you. I always enjoy talking about mice and particularly the linkages of house mice and human history. Thanks so much. Fantastic. And thank you to everyone for listening to our episode today. This has been Gone Medieval from History Hit.

Don't forget that you can subscribe if you haven't already. I'm Dr. Kat German and I will be back again with more essential medieval stories next week. Thank you.