 The theory was advanced in part because of lack of archeological evidence for large @-@ scale Celtic immigration , though it is accepted that such movements are notoriously difficult to identify . Some proponents of this theory hold that it is likely that there was migration of smaller groups of Celts to Ireland , with sufficiently regular traffic to constitute a " migration stream , " but that this was not the fundamental cause of Insular <unk> . Historical linguists are <unk> that this method alone could account for the absorption of the Celtic language , with some saying that an assumed processional view of Celtic linguistic formation is ' an especially hazardous exercise ' . Genetic lineage investigation into the area of Celtic migration to Ireland has led to findings that showed no significant differences in mitochondrial DNA between Ireland and large areas of continental Europe , in contrast to parts of the Y @-@ chromosome pattern . When taking both into account a recent study drew the conclusion that modern Celtic speakers in Ireland could be thought of as European " Atlantic Celts " showing a shared ancestry throughout the Atlantic zone from northern Iberia to western Scandinavia rather than substantially central European . 
