In this millennium (a period extending from the 6th century BC and the 4th century AD), new religious interpretations have risen in India, China and Persia; great philosophers have come to Greece and Egypt; and the center of cultures at that time were moving rapidly in their spiritual understanding from a more or less archaic foundation to the very position which modern religion now occupies. Or actually, the religion as we know it in the world today has not greatly changed since this critical period. During that time, almost all of the spiritual beliefs which we hold to be valid today were rising, developing, unfolding and integrating in the ancient world. Therefore if we go to the great religions of the world, the only important religion that lies outside of this barrier and still survives, is Islam.
Minute 28:00, Youtube Link.