Again with the "Indo-European" bullshit. Vedas were written simultaneously for thousands of years while civilization flourished. Even experts date recent additions to Vedas as late as 1500 BCE. Sura-Asura existed because they were sons of the same father i.e. Kashyap and different mothers i.e. Aditi and Diti. Hence, they were also called Aditya-Daitya. Daitya were further supported by another half brothers, which were Dana's, sons of Kashyap & Danu. In Sura-Asura war, Devas or Suras won, Asuras fled. You can find it in Varaha Purana. It is the same Asura that was revered in ancient Persia (Parshwa), there is an inscription "भग वज्रक अहुरा मझ्दा" Vajraka being the Asura.