Ping.
"If the Celtic dialects are known to linguists and relate to other languages, then this suggests that these people preceded the Celts in Europe, and perhaps were driven back into the district they're in now by the invading Celts."
The Tocharian language A & B is an extinct European language that is most closely related to the ancient Celtic languages. The oldest paper ever found has Tocharian written on it and was found in China. Look to the east for answers.
It is suspected that the red-headed mummies found in the deserts of China spoke Tocharian.
Investigators have also found some physical peculiarities among the Basques, such as there being more of them with type O blood than in the general European population.That's a little interesting, because years ago Barry Fell gave the details of a (misplaced) letter he'd received from a native American. The letter writer had said that he'd once traveled in Spain and one day heard a few men having a conversation in what sounded very much like his own tribal language. When he tried speaking with them, he could make himself understood. :') Type O is overwhelmingly the blood type of native Americans.