No grave, no house plan, no saga: there is still no direct evidence of Norse seafarers on Madeira or the Azores. Even so, the idea has made headlines twice. It rests on mouse bones from Madeira's dunes, on the genes of modern house mice and on traces of dung in Azorean lakes. This article separates what was measured from what was inferred, and follows the dispute that the Azores study set off in its own journal.
Madeira lies a little over 800 kilometres southwest of mainland Portugal, about 1,000 from Lisbon and just over 500 from the African coast, and the Azores sit far out in the open Atlantic. Both groups were considered empty until the Portuguese arrived in the 15th century: Madeira around 1420 in the usual account, the Azores between 1427 (Santa Maria) and 1452 (Flores and Corvo). Yet 14th-century charts already show islands in these waters, so somebody knew of them earlier.
The Viking idea comes from the natural sciences. It starts with animals rather than with a text or a man-made find. House mice live off people and reach distant islands only as stowaways. Their trail leads to a ship, and a ship leads to people. Who those people were is a further step, and the whole debate hangs on it.
The trail begins with a genetic paper that is often misdated. İslam Gündüz and colleagues published it in Molecular Ecology in 2001. The team sequenced the D-loop, a highly variable stretch of mitochondrial DNA, in 44 mice from Madeira, Porto Santo and the Ilhas Desertas. Mitochondrial DNA (mtDNA) passes only through the mother. The 19 variants formed a single group, which suggests one source, and they resembled sequences from Scandinavia and northern Germany.
The authors mentioned Vikings as possible carriers, but stated plainly that no such visit is on record. On historical grounds, they judged Portugal the more probable source at the time, and they lacked comparison data from there. Förster and colleagues supplied it in 2009 with sequences from 156 mice from Madeira and mainland Portugal. The link between Madeira and northern Europe held up, while Portugal showed a common lineage of its own.
The second pillar is age. Juan Carlos Rando, Harald Pieper and Josep Antoni Alcover surveyed sites on Ponta de São Lourenço, the peninsula at Madeira's eastern end, and found mouse bones. According to the press release from the Spanish research council CSIC, there were two samples, one of them too small to date. The other, reported in Proceedings of the Royal Society B, gave a radiocarbon age of 1033 ± 28 BP, meaning years before 1950 on the raw scale of the measurement.
Converted to calendar years, the sources differ slightly: the press release says 900–1030, the abstract says “before 1036”, and later papers citing the study give 903–1036. The “900–1036” in circulation is therefore a rounding, not a measurement. I could not consult the full text of the original paper, so the exact calibration remains open here.
The result still stands out: mice lived on Madeira some four centuries before Portuguese settlement. Förster and colleagues reached a similar order of magnitude by molecular methods; the 2021 Azores study reports their estimate as 910–1185.
Precision matters here, because the two findings come from different material. The dated material is old bone. The northern European similarity comes from living mice. The summaries available to me mention no DNA from the dated bones, and Alcover himself said in 2014 that the Viking suggestion still had to be confirmed by future morphological and genetic studies. So the headline “Viking mice on Madeira” joins two separate results that, as far as I know, nobody has yet tested directly against each other. The 2024 overview by Gabriel and colleagues in Genes, which still argues for a Viking signal, likewise uses only modern animals.
The paper's abstract goes only so far: humans may have reached Madeira before 1036. The Vikings enter mainly through the press release, which also says that no historical records document Norse voyages to Macaronesia, the island world of the Azores, Madeira and the Canaries.
The reasoning is still plausible, and the method has worked elsewhere. Jones and colleagues showed in 2012 that Iceland's house mice probably came from Norway or the northern British Isles and arrived in the early 10th century, which fits the known settlement. Mice reached Greenland from Iceland and later died out there. In Newfoundland the same group found no genetic trace from the Viking period. The difference from Madeira lies in the cross-check: Iceland has texts and excavations, and the mouse merely confirms them.
It sounds like a banal question, yet it hits the weakest point. Geographer Simon Connor, a co-author of the Elias objection discussed below, is quoted in Science in 2021 (according to English Wikipedia; I have not seen the article itself), with the Azores in mind, as objecting that a mouse from Scandinavia could just as easily have boarded a ship in what is now Portugal. The same reasoning applies to Madeira. Trade routes existed, after all. A further point is reasoning rather than measurement: the comparison data come from modern populations. They show only indirectly what mice in Portuguese harbours looked like a thousand years ago.
And mtDNA shows where a mouse lineage came from, not who steered the ship. Norse sailors were not alone on the Atlantic. Archaeologist Søren Sindbæk, asked by Eos about the Azores study, called the result surprising but feasible, and added that other seafaring groups such as Irish monks could not be ruled out.
Seven years after the Madeira find, a far larger study appeared in PNAS. Pedro Raposeiro and a large team drew sediment cores from five lakes: Peixinho (Pico), Caldeirão (Corvo), Funda (Flores), Azul (São Miguel) and Ginjal (Terceira). They looked for pollen, charcoal and two kinds of faecal fat molecules: 5β-stigmastanol, which points to ruminants, and coprostanol, abundant in human faeces but also found in other omnivores, a difference the authors say they cannot resolve. They also counted spores of fungi that grow on dung.
The core claim runs like this: the islands had no large mammals, so these signals must come from introduced animals and people. The earliest values come from Peixinho, with ruminant markers around 700 (−60/+50 years), and Caldeirão around 850 (± 60). Elsewhere the picture starts later: coprostanol appears at Azul around 1280, and Funda shows no faecal trace at all before about 1300. Rye pollen turns up on Pico around 1150 and on São Miguel around 1300.
Sediments say nothing about who was responsible. The authors reach the Norse by way of three other sources: the mouse studies, the timing of the Norse expansion and a climate simulation. For 850 to 900 it shows weakened westerlies and anomalous north-easterlies that would have favoured ships from the north, while sailors from Lisbon, as co-author Santiago Giralt told Eos, would have missed the islands. The authors consider deliberate voyages very unlikely and drift by storm and wind more probable. Their wording is that the Norse were “most likely” the earliest settlers, which is a probability claim and not a demonstration.
The most important of those mouse studies comes from Sofia Gabriel, Maria da Luz Mathias and Jeremy Searle (2015). They analysed 239 sequences from all nine islands and found a mixed picture: several lineages across the archipelago, a link to mainland Portugal on some islands, and an unexpected one to northern Europe on three. They read this cautiously as possible contact before the 15th century. Searle later stressed that they had proposed only a possible visit, since a very short stay is enough for mice, and had said nothing about settlement. Only the sediments turned this, for him, into “substantial” occupation. The debate therefore adds together two claims of different strength.
In January 2022 a group led by Rui Elias replied in PNAS. Their title asked whether there was any solid evidence of widespread landscape disturbance before the Portuguese at all. The main points:
What the group does not claim is striking. It does not deny a human presence before the Portuguese, and it calls Norse presence an “intriguing possibility”, citing the mice. Its target is the widespread transformation and the early date.
Raposeiro and colleagues answered directly. Their age model, they said, rests on terrestrial pollen concentrates and on two volcanic ash layers dated to 650 and 700; the rye points to a local source, and the introduced ribwort plantain Plantago lanceolata to pasture. They concede open questions. The Norse no longer appear in this reply.
Palaeoecologist Valentí Rull, who had worked on Azorean pollen before, took the data apart again in 2023 in the Journal of Biogeography. His commentary offers no new dataset, but it identifies two weaknesses. First, on his reading only the Corvo and Pico records reach back far enough to say anything about the time before 900, so an early settlement of the whole archipelago cannot be derived from them. Second, the climate simulation begins in 850, while the proposed arrival falls between 700 and 850. The study's authors acknowledge this and consider it a fair approximation; for Rull, the inference to the Norse is “unwarranted”.
His result lies between the camps. He sees strong support for a presence before the Portuguese, but he places the first consistent trace in the 13th and 14th centuries, about a century before Portuguese arrival. He does not exclude something earlier. An early medieval Norse settlement, for him, “remains undemonstrated”.
Setting the numbers side by side reveals some further tensions outside the specialist debate. The following points are my own compilation; the data come from the papers named.
The study itself gives the Norse expansion as the Faroes around 800, Iceland around 870, Greenland and Newfoundland around 1000. The earliest Azorean signal around 700 would therefore precede the first stations in the North Atlantic. The Madeira dates used as support are also younger than that signal.
Then there is the livestock. A storm-driven ship sits badly with cattle or sheep that survive on an island long enough to leave traces on a lake bed. Then the duration: the faecal markers run into the Portuguese period. The authors themselves write that so long an occupation should be visible in the archaeological record. And anyone leaving traces on the islands in the 13th century would have been there long after the end of the Viking Age, wherever they came from.
Finally, the first Portuguese accounts describe dense, untouched forest and no people. The study counters that the islands may have looked undisturbed to the newcomers because the damage done by their own settlement was far greater. That is possible, though it fits awkwardly with the “widespread” disturbance that Elias and colleagues challenge.
A comparison shows how much is missing. Newfoundland, the farthest point of Norse voyages, has buildings and finds, and even a precise year for Norse woodworking. For the Azores, Eos asks where the Norse graves and settlements would be, and the PNAS study itself calls the archaeological data scarce and incomplete.
Two sets of finds are often cited but carry little weight. A putative trachyte bowl from Terceira, dated to 1020–1160, is described as controversial by the study itself, and its human origin is, by its own wording, only presumed. The rock-cut chambers reported in 2010/11 on Corvo, Santa Maria and Terceira are, according to the overview I saw, still being studied; their age and purpose are open. Nothing so far connects either with Scandinavia.
Missing finds do not refute the idea, since they may also reflect the patchy state of research. They do limit what can be claimed.
Technically, little stood in the way of such a voyage. Ocean-going cargo ships reached Iceland and Greenland, and Norse fleets knew the coasts of Iberia and the Mediterranean in the 9th century. From there, Madeira is not unthinkable for a ship blown off course. But the texts that record other remote voyages say nothing of this stretch of ocean. Even the detailed account of Sigurd's crusade in the early 12th century stays with the coast.
“After this King Sigurd sailed with his fleet to Lisbon, which is a great city in Spain, half Christian and half heathen …”Snorri Sturluson, Heimskringla, Saga of Sigurd the Crusader and his brothers, section 5, translated by Samuel Laing (19th century)
The silence proves little: a stray freighter that never came home leaves no saga. But such a freighter would be something other than the “settlers” of the headlines.
Two motifs persist alongside the science. One even appears in the PNAS study: the Medici Atlas calls Corvo “Corvis Marinis”, Marine Raven Island, and ravens were a Norse navigation aid. The study does not name Flóki, though his use of ravens in the Landnámabók is the familiar example. This is a weak link. The atlas dates from the 14th century, sources differ on the year (1351 or 1370), and the name is Latin. Corvus marinus means sea raven, and the word cormorant probably derives from it. A bird's name does not need a Scandinavian godparent.
The other is the equestrian statue of Corvo described by Damião de Góis in the 16th century: King Manuel I supposedly had it fetched, and it broke in transit. Some think it invented or a rock formation, others defend de Góis. According to de Góis only fragments reached Lisbon; no remains are known today. The same goes for the reported Carthaginian coins from Corvo. Neither has anything to do with Vikings, though popular texts like to mix them in.
Were Vikings on Madeira? This cannot be clearly established. The dating puts mice there around 1000, which implies a ship that landed, and the mtDNA points to northern Europe. Direct evidence of Norse people is missing.
Were Vikings in the Azores? That is also unproven. Even Rull's critical commentary considers people there before 1427 well supported. That they were Norse, he regards as undemonstrated.
Is the date 900–1036 correct? As a rounding, yes. The measurement was 1033 ± 28 BP, and sources give calibrated ranges of 900–1030 or 903–1036. It dates one mouse, not the arrival: the animals may have come earlier.
What would settle the question? The strongest evidence would be a Norse archaeological context and ancient DNA from the dated bones. Rull also names sediments older than 1200 from Flores, Terceira and São Miguel as a gap.
Vikings in Spain · Vikings in the Mediterranean · Vikings in the North Atlantic · Vikings in the British Isles · Viking navigation · Viking ship types · Vinland 1021
Vikings in the Mediterranean · The Vikings in Ireland, Scotland & the Isles · The Vikings in the North Atlantic – From the Faroes via Iceland and Greenland to Vinland · Vikings in Spain · Raven-Flóki.
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