I am not an archaeologist or expert on the Azores, but if archaeologists and historians believe that the Azores were uninhabited prior to the Portuguese colonization, then of course it could not have been Vikings that introduced these lineages directly to the Azores. In this article I examine only genetic information, which should be taken into consideration with other types of information.
I-Z141 formed and diversified 2100 BC, likely in northern Germany or Scandinavia, well before the Vikings. To determine which of its lineages were spread by Vikings rather than other groups, it is necessary to look at branches that diversified during the Viking Age and are present in the Viking homelands of Scandinavia and in the places they subsequently settled.
First, lets enumerate possible vectors by which NW European Y-haplogroups could have entered the Azores, in descending chronological order.
Flemish, before 1490
By 1490, there were 2,000 Flemings living in the islands of Terceira, Pico, Faial, São Jorge and Flores. Because there was such a large Flemish settlement, the Azores became known as the Flemish Islands or the Isles of Flanders. Prince Henry the Navigator was responsible for this settlement.
I-Z141 may have been introduced to Flanders by Vikings, Weser-Rhein-Germanic tribes, Celtic tribes, or it may have been there since the Bronze Age expansion of I-Z141, given that Flanders is not very far from Southern Scandinavia / Northern Germany, the presumed locus of I1 and immediate subclades.
The initial waves of settlement were by Portuguese, who may have had haplogroup I-Z141 for a variety of reasons:
- 8-11th Centuries - From Vikings
- 5-7th Centuries - From Germanic tribes Vandals, Suebii, Visigoths, Buri who had invaded and established kingdoms in Iberia
- before 6th Century BC - Celticisation of Iberia, supposing the Celts had a Central European homeland, it is quite possible that some I-Z141 may have been present in these homelands before the Celticisation of Iberia
It is important to note that, according to Wikipedia 2/1/2019 - "Solid confirmation of a pre-Portuguese human presence in the (Azorean) archipelago has not yet been published. "
So it would seem unrealistic to assume Viking colonization of the Azores unless we have very strong Y-DNA circumstantial evidence.
Now let's examine A14984, the most diversified subclade of I-Z141 with Azorean presence. Given that all three Azorean samples have a TMRCA going back to only 175 years ago, we cannot yet infer a presence in the Azores dating back to the Flemish settlement let alone back to the initial Portuguese settlement. So it could have been introduced along with the Portuguese, the Flemish or later.
Its siblings are basal FGC19077, a Swede and a German who, along with these Azoreans, share a common ancestor who lived 1950 years ago. This geography, encompassing Scandinavia and Central Europe, and the timing of the diversification more closely fit the Great Migrations of Germanic peoples throughout the Roman Empire than it does the Viking Age. Coupled with the lack of hard evidence of pre-Portuguese settlement, the Viking case seems weak. While it is interesting to note that Norwegian house mice may have been introduced to some Azorean islands by Vikings, the modern Y-DNA circumstantial evidence is not strong enough at this time. Instead, I will address the remaining theories - Flemish vs Portuguese colonization.
If the ancestors of these Azoreans came from 15th Century Flanders, it would mean that the ancestors of A14984 entered into a bottleneck in their Scandinavian/North German homeland starting around 100 AD. Then they moved to Flanders either immediately as Weser-Rhine-Germanic speakers or later as Vikings. It seems less likely that they were there already in Flanders at that time as Celts given the presence of a sibling in Sweden, which lies outside the core Celtic area.
Unless all their kin died out in Flanders or nearby, we should eventually find A14984 in or around Flanders, especially in the communities where Henry the Navigator recruited colonists (or also in Scandinavia if they had been Flemicised Vikings) and not in mainland Iberia (because they went from Flanders to the Azores, bypassing Iberia).
On the other hand, if the ancestors of these Azoreans instead came from Portugal during the Portuguese colonization, we would expect to find A14984 in mainland Iberia.
In conclusion, since at present we lack diversity of A14984 in all three regions of Scandinavia, Flanders and mainland Iberia, I do not conclude that one or the other theories is more valid. But direct Viking origin seems like more of a stretch than either of these theories.
FGC19077 has two other siblings.
A1395 is confined to the British Isles with no presence in Scandinavia. However its TMRCA lived 900 AD and has three lineages in Scotland, Wales and the Isle of Man. These regions are not all especially known for Viking colonization, so while the timing of the expansion fits the Danelaw, this could have been a native British haplogroup which had migrated to the British Isles during the Bronze Age.
The other sibling Y6900 is quite diverse, yet appears to have not originated in Britain. Only Y6885 appears British in origin, which diversified in Scotland and England during the Danelaw after emerging from a 2000-year bottleneck since diverging from its sibling in Västernorrland County, Sweden in 1300 BC. This period was a time of upheaval with the Tollense River battle in Baltic coast Germany and the Bronze Age Collapse of Mediterranean civilizations.
It seems likely that Y6900 may have been a Scandinavian, some of whose progeny may have been involved in Germanic and Slavic peoples' ethnogeneses, some of which may have occurred during the Viking age though the earlier diversification dates in central Europe of some subclades point to Migration Period Germanic tribal affiliation. This is not unexpected as the ancestors of these West and East Germanic-speaking peoples are assumed to have lived in Scandinavia.
Another Azorean subclade of I-Z141 is Y15150>Y31062. This subclade has little diversity and just two geolocated samples, from the Azores and Peru. Knowing whether the Peruvian's ancestors came from the Azores or from mainland Iberia would be informative.