Eli5. What decides an animals longevity as for as mortality? A horse, way stronger and healthier than most humans, live only to around 20 to 30 years, yet the steady rate when humans expire is around 70 to 80 years. How does this work?
In: Biology
All living things have DNA. In humans and other animals this DNA is arranged in chromosomes. The chromosomes have caps on the ends that protects them called telomeres. Every time a new cell is made oh, the telomeres get shorter. As the telomere has run out, you see the signs of aging. At some point the organs become inefficient and the body eventually shuts down.
The faster a speices cells divide, the longevity of their organ tissue, the efficiency of their kidneys and liver, and their diet and lifestyle all factor into age.
Human tissue is pretty long lasting compared to most species, as cells divide DNA is slowly broken down, until cancer or organ failure or a dozen other diseases set in.
Certain animals take longer or slower to grow, depending on their complexity or their environment. When you grow, your cells start to multiply super fast. The longer they have, the more thorough they can be and the less mistakes they will make, leading to differences in lifespan.
Mammals specifically have a heartbeat average. An average amount of total heartbeats over a lifespan across a species. It has proved pretty accurate. So if you know the average beats and average beats per minute this leads to average longevity. As to why I don’t know.
Longevity might be partly decided by natural selection… A creature with a certain combination of anatomical/physiological features and behaviors living in a certain habitat will die eventually from causes not related to aging, such as predation, accidents, diseases, even if it could otherwise theoretically never die of old age. And so the genetic code of that species simply isn’t “built” to function very long past the average amount of time that the creature would normally live. This is also related to the span of the creature’s reproductive life.
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