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MedicineWhen a human limb is amputated, how does the circulatory system redirect blood flow?(self.askscience)
Given that part of the circuit of circulation has been cut out when one has a limb amputated, how do...
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so...im curious..why don't we humans have the ability to regrow limbs and other organs?
For the same reason that we develop scar tissue instead of fresh new skin. At some point in our evolutionary timeline it took substantially less energy to regrow scar tissue over an area than to have it regrow the way we lost it. Early humans (and earlier ancestors) usually didn't have that many extra calories to work with and had to conserve what they could.
Read this.
Doesn't really give an answer other than "because we're complex and the cells are specialised" then gives the counter-example of amphibians and says that they can do it and we shouldn't be surprised because they metamorphosise.