So just curious. Why does our bodies and organs and muscles start deteriorating at a certain point in our lives? And how come some mammals can live to be 300 years old meanwhile others are lucky to live a couple years?
In: Biology
Stem cells are a big part of this. Much like the ship of Theseus your body is constantly replacing itself with new cells.
This copying process has a downside: over time errors get made, and we exhaust our stem cells which in turn reduce the body’s ability to regenerate damaged tissues and maintain organ function.
Another factor around lifespan is body size relative to disease volume. I recall a study/hypothesis around why whales live so long and it was suggested that it’s because the _amount_ of things like cancer relative to their total mass (think % of cells in body) is lower than say a human. In addition to any variance in say, stem cell reservoirs.
What mammals live to 300 years old?
Many mammals are short-lived for a couple reasons. One, smaller animals often have much faster metabolisms so their lives are shorter. They literally live life “faster” than us; because of this, heart rate is actually a pretty good heuristic for how long an organism will live.
Another factor is environment. Many animals live in dangerous environments that kill them much sooner than old age would. You might see longevity statistics for a wild animal in one place and captive stats for another; this might seem to widen the gap of lifespans considerably, when in fact it’s just comparing apples to oranges.
Raymond Pearl based his Age of living theory upon the earlier work of Max Rubner and proposed that the maximum lifespan of an animal was related to its metabolic rate sometimes viewed as the number of heartbeats. However this may only be part of the picture with the role of reactive oxygen species in cell deterioration and eventually cell death also playing a part. https://youtu.be/ctEIbPI6A4U
Our bodies age because our cells wear out over time. This happens due to telomeres, which are protective caps on our chromosomes that shorten each time a cell divides. When they get too short, cells stop working properly. Damage from things like sunlight and pollution plays a role too.
Some animals live longer because they have better genes for repairing damage and slower metabolisms that leads to less oxidative stress, allowing them to age more slowly and live longer.
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