There's probably no way to prove that this hasn't happened. Anyone who realizes they're not aging normally would likely have taken on a new identity elsewhere for fear of:
1. being burned at the stake
2. being trialed in repeated experiments
3. being deified, and then subsequently being burned at the stake.
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I realize my comment sounds like a joke, but I'm entirely serious. If you or I found out we're not aging normally and look e.g. 25 by the time we reach 40, or 30 by the time we reach 45, would either of us remain in our current lives?