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Not OP, but: > The human heart has only limited self-healing powers and a limited regenerative capacity. A damaged heart muscle and the resulting loss of funct

Not OP, but: > The human heart has only limited self-healing powers and a limited regenerative capacity. A damaged heart muscle and the resulting loss of function can usually not be fully restored. The reason for this is that heart muscle cells in the adult organism have largely lost their ability to divide. > https://www.mpg.de/17679417/heart-regeneration-after-reprogramming-of-cardiac-muscle-cells https://www.mpg.de/17679417/heart-regeneration-after-reprogr...

michaelrpeskin 3y ago
Yes, good find. One description that always resonated with me is the tradeoff between capacity for repair and uncontrolled repair or cancer. Think of two extremes: 1) no capacity for repair: once something is damaged, the cells don't divide and you lost functionality. But there can be no run-away growth or cancer. 2) infinite capacity for repair: damage cells can always be repaired but a bad instruction can cause run away division and growth and become cancerous. So evolution has to figure out where to turn that knob. Do you want to allow repair at a risk of cancer? Generally things that didn't get "injured" evolved to reduce repair capacity. Rarely (ever?) do you hear of heart or eye cancer. Those cells just don't have much repair capacity. But think of skin. That's always getting damaged, so it makes sense for there to be more capacity of repair there at the cost of more cancer. It's all tradeoffs. And it can change over (generational) time. Consider a warring population, if people are getting killed younger before they have the time to get cancer, then that population will end up with more capacity for repair because it makes more sense for survival to repair because cancer never gets involved. And the converse can happen, when long life becomes the norm then the tradeoff change and cancer prevention is more beneficial than total repair capacity. Just painting with broad strokes here, it's not exact, but a trend that does show up between populations.

michaelrpeskin 3y ago

Yes, good find. One description that always resonated with me is the tradeoff between capacity for repair and uncontrolled repair or cancer. Think of two extremes: 1) no capacity for repair: once something is damaged, the cells don't divide and you lost functionality. But there can be no run-away growth or cancer. 2) infinite capacity for repair: damage cells can always be repaired but a bad instruction can cause run away division and growth and become cancerous. So evolution has to figure out where to turn that knob. Do you want to allow repair at a risk of cancer? Generally things that didn't get "injured" evolved to reduce repair capacity. Rarely (ever?) do you hear of heart or eye cancer. Those cells just don't have much repair capacity. But think of skin. That's always getting damaged, so it makes sense for there to be more capacity of repair there at the cost of more cancer. It's all tradeoffs. And it can change over (generational) time. Consider a warring population, if people are getting killed younger before they have the time to get cancer, then that population will end up with more capacity for repair because it makes more sense for survival to repair because cancer never gets involved. And the converse can happen, when long life becomes the norm then the tradeoff change and cancer prevention is more beneficial than total repair capacity. Just painting with broad strokes here, it's not exact, but a trend that does show up between populations.