Haplogroup X was called European DNA because it was thought that it only occured in Europe. If it were actually European than one of the founding maternal lines would have had to have come from Europe. Now that X has been found in the Altai the case for Europe is pretty weak.
How does that relate to the possibility that all of todays Indo-Europeans originated in/around the Gansu Province region in China?
On another point. James Chatters (of Kennewick Man fame), thinks that Kennewick Man came from a line of people that spawned both todays Asians and Europeans.