Nature's Immortals

Four very different escape routes from aging:

• Hydra — endless cell replacement, so it never wears out.
• Turritopsis — rewinds to its baby stage and grows up again.
• Lobster — lifelong telomerase keeps its cells young, until molting wears it down.
• Naked mole rat — long-lived, fertile, and remarkably cancer-resistant.

No single trick — many separate answers to the same problem.