Because 1) I2a-L126 was found on Pabay Mor (off the West coast of the Isle of Lewis), in the Outer Hebrides, who lived c. 1311 BCE, and I2a-M284 was found in New Grange (the "incest" god-king), in Ireland, who lived c. 3522 BCE. M284 is pre-Bell Beaker and L126 is pre-Celtic. My line (West/Isles...