According to "A Buddhist Genesis" (Aggañña Sutra origin myth, DN 27), humans on Earth during this cycle originated by devolution. This began at the beginning of the aeon as deva beings descended from the Ābhāsvara deva realm.They were beings shining by their own light, capable of moving through the space without mechanical aid, long lived, not requiring material sustenance but instead feeding on something more subtle.
Over time, they acquired a taste for physical nutriment. And as they consumed it, their bodies became denser and more as human bodies are now. They dimmed and began to acquire differences in appearance. Their lifespans shortened.
They differentiated into two sexes and became sexually active. Greed, theft, and violence arose among them. They consequently established social distinctions, government, and appointed a ruler called Mahāsammata ("the great appointed one"). Some of the kings of India in the Buddha's day claimed to be his descendents.
