"Iranianist H. Humbach, too, emphasises the same similarity pointing out the polarisation of relations between the Ahuras and the Daevas in the Gathic Avesta and the reverse polarisation between Devas and Asuras which only begins to occur in the later books of the RV; he concludes: “All this suggests a synchrony between the later Vedic period and Zarathustra’s reform in Iran” (1991:23)."