This Sutta is, in some respects, something like a Buddhist equivalent to the Genesis creation account (although its account of the origins of the world and of humans is quite different!). “Agga” means “highest,” and so the Sutta, delivered to the two brahmins Vāseṭṭha and Bhāradvāja, refers to the “highest knowledge” about the world. The Buddha teaches them that all living beings on this planet have their origins in the Brahma realms at the beginning of the creation of the Earth, meaning that every currently living human was once a Brahma.
Brahma-loka, in Hinduism and Buddhism, the realm of the universe in which pious celestial spirits dwell. Theravada Buddhists believe that the the brahma-loka consists of 20 separate heavens, with the lower 16 being material (rūpa-brahma-loka) and each realm being progressively more subtle and approaching immateriality. Such Buddhists believe that rebirth in the brahma-loka results from a great deal of accomplishment in meditation and virtue, as well as his understanding of the formlessness of the universe. This realm, however, no less than any other, is in a continual cycle of change, destruction and re-creation.
This Sutta teaches that the universe is eternal and has no beginning and that it consists of clusters of stars, of which ours is one of “10,000.” Every few billion years, a star in the vicinity of these worlds explodes and devours the physical worlds and inhabitants in that vicinity. Although these physical worlds are destroyed, the subtler Brahma worlds survive, as they are of a subtler or finer density that is not as subject to destruction from physical matter in the way that bodies of the coarser realms are. Inhabitable planets eventually reform, resulting in humans reborn as very light, Brahma bodies.
As the Sutta details, prior to our incarnation as human beings, we were immaterial, purely spiritual beings who only later became stuck in physical bodies after becoming inordinately attached to the pleasures of the physical world over a period of time. When this happened, we lost memory of the Brahma bodies by which we had been constituted. These ideas are similar to Ken Wilber’s writing on consciousness beginning in an immaterial or subtle plane that begins an “involution” from spirit to matter, which consists of an “outward arc” where the spirit is lost in the material world of illusion, to progress through an evolution by which it gradually returns to the spirit world through an “inward arc”; a process he refers to as the “pre/trans” cycle.