20 Biological Immortality SOME FACTS ABOUT AGING AND IMMORTALITY Let us proceed to demolish superstitions. Is aging universal? Clearly not. If everything aged, the continued survival of the cells responsible for producing our sperm and eggs (the ‘germ- line’) over millions of years would have been impossible. Most of the bananas that you have eaten in your lifetime come from immortal clones produced on plantations. Even in organisms like mammals, which have germ-lines that separate very early from the rest of the body, the survival and replication of the cells responsible for producing gametes (germ cells) have pro- ceeded for hundreds of millions of years. Life can continue indefinitely. But even if life can propagate itself indefinitely, are there any organisms that are free of aging, living with biological immor- tality? I must be clear about one point concerning death: It is not true that aging is required to kill organisms kept in the laboratory. Showing that a species dies in the lab is not the same thing as showing that immortality does not occur in that species. Mechanical accidents in the lab will kill many soft- bodied  plants,  animals,  and  microscopic  creatures.  Deadly mutations can kill at any age or time. It is also impossible to keep living things free of all diseases indefinitely. Being free of aging does not imply the complete absence of death. Biological ‘immortals’ will often die, just not because of a sys- tematic, endogenous, ineluctable process of self-destruction. Death  is  not  aging.  Biological  immortality  is  not  freedom from death. Instead, the demonstration of immortality requires the find- ing that rates of survival and reproduction do not show aging. There are many cases where such patterns are inferred anec- dotally among plants and simple animals, like sea anemones. But the best quantitative data known to me were gathered by Martinez [2], who studied mortality rates in Hydra, the