R-L4 Y-DNA Haplogroup is a subclade of the R-U152 Haplogroup. The current descendants of the L4 paternal ancestor (likely born about 700 CE) are of Ashkenazi Jewish ancestry. The recent discovery of an L4 individual in the Erfurt Jewish cemetery excavation shows the Medieval presence of these descendants in Germany in the 14th century. You can read about the DNA results from the cemetery and the scientists' conclusions here in the Journal, "Cell"