Complex sentence: However, the Bulgarians and most other South Slavs are characterized by a prevailing genetic substrate that is different than that of the East-West Slavs, the two groups are separated sharing only a modest gene flow.
Split into simpler sentences: However, the Bulgarians and most other South Slavs are characterized by a prevailing genetic substrate that is different than that of the East and West Slavs. The two groups are separated sharing only a modest gene flow.