A high level look at the search for the roots of regeneration in lower animals: "Each year, thousands of Americans lose fingers, hands or entire limbs in terrible accidents. Prosthetics can help amputees regain some function, and successful hand transplants have recently been achieved. But wouldn't it be great if humans could simply regrow missing parts on their own? Within the space of a generation, this seemingly superhuman power might become a reality, scientists say, and people may have a lowly amphibian to thank for it. Among the world's varied creatures, a Mexican salamander called the axolotl appears best at regrowing whole limbs lost to injury. And researchers are hot on the trail of finding out what the axolotl has that humans don't. ... Other animals can regrow complex segments of themselves (many fish regrow lost fins, for example) and the common frog has potent regenerative powers as a tadpole but loses them mysteriously as it matures. ... work with both the axolotl and the frog have turned up interesting clues to regeneration. ... [researchers are] busy comparing regenerative processes in the axolotl to those found in the tadpole but not in the mature frog. ... That will give us a handle, we hope, on why the frog loses the power of regeneration." Which should lead to insight into why humans do not regenerate, and how to induce that regeneration artificially.