Starfish can re-grow arms; lizards can sprout fresh legs; and, hell, flatworms can essentially rematerialise from barely nothing. So why can't humans do the same?
Well, we can regenerate a little -- wounds heal, after all -- but we lack a fundamental ability to do anything more than repair small quantities of damage. In this video, SciShow explains what other creatures have that we're missing, and how, one day, we might just be able to grow a new limb too. [SciShow]