The reason being for this is that after menstruation and child birth, they needed protection from the cold and other weather elements to raise and feed thier children.
The women would have gathered wild fruits, seeds, and berries where they brought them back to thier campsite.
They probably spent most of thier time in those dark tepees and only occasionaly did they most likely wander out of thier tepees to collect the fruit of the plains.
The people sent there over the centuries came from either the Bay of Biscay or from the western coasts of Ireland which they may have used as a repair and resting staion.
From the Bay of Biscay, they brought any needed tools, livestock and nets.
It is positively sure that a few of the O rhesus positive women joined the O rhesus negative tribe, but a lot of the women travelling to southern Europe just below the Swiss alps likely still had the O rhesus negative factor while those travelling north of the glaciated Swiss alps likely had the O rhesus positive factor.