Anonymous asked in Science & MathematicsZoology · 1 month ago

Why can't humans and other animals regrow limbs but other parts of our body can heal such as skin?

I know that a starfish can regrow limbs and many other creatures can. Why can't mammals and birds regrow limbs?

3 Answers

  • 1 month ago

    The heart of neonatal mice have enormous regenerative capacity. It mostly has to do with stem cells.

  • Dixon
    Lv 7
    1 month ago

    They are just too complex to grow from a severed surface. Skin and bone can regrow and knit breaks because it is essentially just extending a material by making more of the same. But if you were severed just below the shoulder, the regrowth would need some way to start an elbow, a wrist, fingers all that cartilage and so on and sort out how to join up the veins and nerves etc. 

    The other things is, that is not how we grow limbs in the first place, ie we don't grow them outward from a surface.

    Creatures such as crabs that can regrow limbs (often rather poorly) have a much more simple limb structure, which is an aspect of just being absolutely smaller. And since mammals can't regrow limbs, the evolutionary pressure is to repair the surface injury, ie skin.

  • i'm  just  gonna'  speculate  about  this … perhaps  mammal's  genome  was  not  programmed  to  replace  such  appendages.  bone  tissue  does  grow,  however.

    for  instance,  if  someone  breaks  a  bone … the  doctor  then  "sets"  the  bone  with  a  splint  or  a  sturdier  brace … over  a  week  or  two … you  can  actually  see  microscopic  filaments  joining  the  two  pieces  of  bone.  x-rays  can  show  evidence  of  this  phenomena.

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