But we are being specific, only this branch of I2a1 is identified as Slavic in origin. Not all I2a1 is Slavic in origin, but I2a1b2, defined by SNP L621 is.
http://s13.postimg.org/ossn8zu7r/I2a1b2a1.png
Origin in Poland 2200 years ago, also found in North Greece. There ya go.
family tree DNA project members who marked themselves on map belonging to this clade:
http://s25.postimg.org/rpfih2i67/map...w_22102015.jpg