"And the LORD God said, Behold, the man is become as one of us [extraterrestrials], to know good and evil; and now, lest he put forth his hand, and take also of the tree of life, and eat, and live for ever: Therefore the LORD God sent him forth from the garden of Eden, to till the ground from whence he was taken." -- Genesis 3:22-23
Mintowt-Czyz, L., Turritopsis Nutricula: The World's Only Immortal Creature, The Times, Jan 2009
Turritopsis nutricula may be the world’s only “immortal” creature.
Jellyfish usually die after propagating but Turritopsis reverts to a sexually immature stage after reaching adulthood and is capable of rejuvenating itself.
The 4-5mm diameter creature, technically known as a hydrozoan, is the only known animal that is capable of reverting to its juvenile polyp state.
Theoretically, this cycle can repeat indefinitely, rendering it potentially immortal.