Most of the body doesn't regenerate because there was not enough evolutionary pressure. Even with regeneration you could still easily die from some severe injury, blood loss or disease. While salamander regeneration is impressive, it has its limitations. For example, no known adult salamander can regenerate an entirely removed eye. Also if you chop a salamander, it will not regenerate like a Planarian worm, it will just die. And a fun fact, Axolotls can regrow a limb yet cannot regenerate an adult eye lens.
Also, although the article is mostly true, there are some inaccuracies:
>> Neurons and cardiac muscle cells don't reproduce after childhood
There is some evidence showing a slow cell turnover in cardiac muscle, estimated around ~1% per year in young adults, falling toward ~0.5% in older people. Most neurons don't regenerate, but there an evidence that some parts of the adult brain (such as hippocampus) still produce new neurons, although the number is very low.
Liver regeneration is not perfect either: <a href="https://www.youtube.com/watch?v=rOv7Sr3X-eo" rel="nofollow">https://www.youtube.com/watch?v=rOv7Sr3X-eo .
> Most of the body doesn't regenerate because there was not enough evolutionary pressure.
All basal metazoan branches (ctenophora, porifera, placozoa, cnidaria) have species that are capable of whole body regeneration, so this trait was likely lost on the bilaterian branch (which includes chordates like ourselves). If anything, there are evolutionary pressures to loose this trait.
I read a book on epidemics where some modern theories on death were essentially its selected for to force potential infecting organisms to keep starting over on mastering a given genetic environment. Ones grandchildren are more likely to survive the successor plague than you are, hence a population with excessively long life would have died out. I think the evidence was from long lived trees? (Pandemic by Sonia Shah).
senfiaj · · focus · HN ↗
Also, although the article is mostly true, there are some inaccuracies:
>> Neurons and cardiac muscle cells don't reproduce after childhood
There is some evidence showing a slow cell turnover in cardiac muscle, estimated around ~1% per year in young adults, falling toward ~0.5% in older people. Most neurons don't regenerate, but there an evidence that some parts of the adult brain (such as hippocampus) still produce new neurons, although the number is very low.
Liver regeneration is not perfect either: <a href="https://www.youtube.com/watch?v=rOv7Sr3X-eo" rel="nofollow">https://www.youtube.com/watch?v=rOv7Sr3X-eo .
burning_hamster · · focus · HN ↗
All basal metazoan branches (ctenophora, porifera, placozoa, cnidaria) have species that are capable of whole body regeneration, so this trait was likely lost on the bilaterian branch (which includes chordates like ourselves). If anything, there are evolutionary pressures to loose this trait.
lanstin · · focus · HN ↗