The ancient L283s all downstream from Z615 (Z38240 Dalmatian/Illyrian , CTS6190 Etruscan, Z631 Roman, and the Z615 Mokrin/Maros) had healthy amounts of steppe ancestry (around 30% autosomal steppe) with no autosomal ancestry from near east/Anatolia.
The Z600 and basal L283 from Sardinia had no Anatolian/near eastern autosomal ancestry, but also had very little to no steppe ancestry. Bit of a head scratcher, but probably the result of being part of an isolated population in Sardinia for many centuries. These Sardinian L283s were from the Naragic Civilization, which descends from Bonnanaro and Polada Cultures from northern Italy = Bell Beakers.
Ancient L283/Z600 in Sardinia and Z615/Z597 in Balkans point to north —-> south migration from a possible homeland in/near Central European Alps. I’m under the impression that L283 is a Caucasian haplogroup and crossed the southern steppe en route to Central Europe based on ancient basal L283 from Karbino Balkaria in southern Russia and current living kits from Armenia. We need more ancient samples from area between Balkans and Karbino Balkaria to confirm this path, though.
https://www.yfull.com/tree/J-L283/