[ThanhPhero]

There was likely little or no trade involving non Scandinavian ships a thousand years ago. It likely that the Vikings who settled Iceland went out on raids in the British Isles and NW Europe and took their brides as part o their booty. They carried very few or no women with them on their riding voyages.

[Tallguy]

That was my first thought: that the female line descends from captives taken in raids on Scotland, Ireland, etc.