I was on Crystal aka rustykeloid's deviantart looking at her new art... and someone commented on her Jelly Fish pic saying that a Jelly Fish was found that is biologically immortal. I had an immediate - holy shit - moment, and of course had to wiki it.
What I learned:
Jelly fish start out as little polyps, then they hatch and reach sexual maturity within weeks, and after laying eggs, they die. The Turritopsis nutricula, is different because when it reaches sexual maturity and lays its eggs, it starts to revert back to the polyp stage. It goes from baby to adult, then adult to baby, and repeats the process indefinitely, or until it's nervous system is removed.
According to wiki:
The umbrella turns inside out; middle section and tentacles are reabsorbed before the polyp spawns. Stolons form two days before the polyps differentiate. The ability to reverse the life cycle is probably unique in the animal kingdom, and allows the jellyfish to bypass death, rendering the Turritopsis nutricula biologically immortal. Laboratory tests showed that 100% of specimens reverted to the polyp stage.
So it's true. This creature has discovered its own little fountain of youth. Now as fascinating as this is, I have to say that I don't think humans would be able to cope well with having to revert back to children/babies, and then go through puberty over and over... the emotional baggage would be pretty severe I think. But that's assuming we'd retain all of our memories from our childhoods and adulthoods. If we didn't retain our earlier lives, or regenerations, then it would be like reincarnation, only within the same body.