Balkans is original homeland of Serbs because ethno-genesis of Serbs were in the Balkan in Middle Age.
Original holders of Serbian name are not same as modern Serbs.
There is theory that proto-Serbs were Alan (Iranic) tribe Serboi.
Serboi were probably R1a-Z93, G and R1b-Z2103.
R1a-Z93 were the main haplogroup among Iranic people, G is most common among Ossetians (they are known as descandants of Alans) and R1b-Z2103 is present among Ossetians and exist in France and Spain (came with Alans) [video]https://upload.wikimedia.org/wikipedia/commons/e/ea/Alani_map.jpg[/video]
R1a-Z93, R1b-Z2103 (quite common among Albanians) and Caucasian branch of G does not exist among Serbs and if Serbs are related with Serboi then this haplogroup shoulds be present among Serbs.
By the way original homeland of all humans is Africa.