In Spider-Man comics, scientist Curt Connors injects himself with a serum based on lizard DNA and re-grows his amputated arm. He also transforms into a giant humanoid lizard and becomes evil. Unfortunate side-effects aside, the Lizard’s story reflects a real and longstanding scientific quest – to understand the extraordinary regenerative powers of animals, and duplicate them in humans.

If I cut my arm off, I will end up with a permanent stump that’s covered in scar tissue. By contrast, if a newt or salamander loses its leg, it will grow a new one. The wound will close and, over time, it will create new bones, muscles, nerves and skin.

Healing powers of this kind were first discovered in 1740, when Abraham