Hello all!
Though ordinarily it is often considered inappropriate to mention another website on a forum, I was invited to do so. On Trueimmortals.net, we have been investigating the possibility that there in fact are some people in the world who do not age normally. One class, the "true immortals," would not age at all. The other, which we whimsically called "Hafeems" or "half-immortals," would age very slowly. The underlying theory is that of a biological aging clock with various set points.
We hypothesize that such people would try hard not to be discovered, for two primary reasons: In past centuries, such a person would be assumed to have "sold his soul to the devil," and would face the risk of religious prosecution. Complementary to that, it appears likely that a person who could in principle live forever might be much more cautious, less willing to take risks, than a person who has only a finite lifespan at risk. But this requires a person to continually change location, when his or her lack of aging becomes apparent. Doing so would have become more difficult in recent years, with the invention of such things as photographs, fingerprints and social security numbers.
Trueimmortals.net has been going on some time, and the story detailed there has become complex. However, a recent post may be a good introduction, with links in the post that set out the major issues: http://www.trueimmortals.net/?p=2684
-- Stephen