Some genes allow for longer life than other genes. Some creatures have genes that program them for death in days. Other creatures are programmed to live for decades if they manage to escape catastrophe.
A creature that lived a little longer than others within its species allowed for a gene mutation that produced a longer life. Eventually, those within a species with longer-life genes became dominant within their species.
Some creatures were better able to defend themselves, like tigers through their size and strength, or humans by their adaptability, or turtles with their tough shell. These creatures have genes developed across a great span of time that give them a normally longer life than that of smaller, weaker and more vulnerable creatures. Small birds that can defend themselves by flying away from danger have genes that give them a normal life of a decade or more. Mice, on the other hand, cannot escape by flying away and die of old age in a year or two.
Energy use might be involved in longevity. A change in the environment that produced a shorter lifespan lent greater survivability to those members of a species that were more genetically oriented toward putting energy into reproduction rather than bodily repair necessary for longer living. Their genes evolved toward a shorter life span. Energy involvement worked against the hummingbird's speed and ability to defend itself through flight. A hummingbird's extremely fast wings consume vast amounts of adenosine triphosphate (cellular energy molecules) and cause the hummingbird's heart to deteriorate with permanent and long-term wear. This results in hummingbirds usually dying shortly after reproducing.
Creatures, like the humming birds, wear themselves out. And so too do humans. Deaths make space and the dead are replaced by newborn infants – a regeneration of the human species.
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