Gaelic preceding Brittonic in Ireland?

From: Michael Smith
Message: 33045
Date: 2004-06-03

It is conventionally believed that Gaelic preceded Brittonic speech
in Ireland. But couldn't Brittonic have come first, Gaelic speakers
arriving later from Northeastern Iberia? From the web site Ireland's
History in Maps I found the following info, though I'm not sure how
true it is:

the Erainn would have included the Menapii, Bolgi/Builg/Belgae/Fir
Bolgs and the tribes in East Ulster, the ancestors of the later Dal
Riata and Dal Fiatach (aka Uliad) and also the tribes in Connacht-
the Ui Maine and the Conmaicne. It seems that these would have
originally been Brittonic-speakers from Gaul.

the Laigin originally coming from Armorica (thus Brittonic
speakers?), and the Domnann and Gaileoin also being of this region
(Leinster) , so these would appear to have originally been Brittonic
as well.

The Iverni, too, appear to have originally been Brittonic.

This would leave the Goidels (including the later Dal Rhiada-
the "Scots", including the Robogdii) as having been the bringers of
Gaelic speech, perhaps from NW SPain?

Thoughts?

-Michael