Full Idea
The doctrine of a cycle of rebirths and reincarnations that are normally required before one achieve nirvana was only proposed in the eighth century CE, and then spread like wildfire among Hindus and, to a lesser extent, among Buddhists.
Gist of Idea
The Hindu doctrine of reincarnation only appeared in the eighth century CE
Source
Owen Flanagan (The Problem of the Soul [2002], p.166n)
Book Reference
Flanagan,Owen: 'The Problem of the Soul' [Basic Books 2003], p.166
A Reaction
Intriguing. Plato had proposed it in the fourth century BCE. Presumably Hindus had always been dualists, and then suddenly saw and exciting possibility that followed from it. The doctrine strikes me as (to put it mildly) implausible.