Regenerating severed limbs may simply be a matter of flipping a few molecular switches, research suggests.
German scientists have been able to regrow the head of a flatworm in their laboratory by altering genetic circuitry.
They say the experiment sheds light on how the loss of body parts could one day be reversed.
Study leader Jochen Rink, from the Max Planck Institute of Molecular Cell Biology and Genetics in Dresden, said: "We thought we would have to manipulate hundreds of different switches to repair a regeneration defect; now we learned that sometimes only a few nodes may do."
Asked if the discovery might be applicable to more complex forms of life, including humans, he added: "We showed that by comparisons amongst related species we can obtain insights into why some animals regenerate while others don't - that's an important first step."
Why some animals, such as frogs and flatworms, can regenerate and others cannot remains an unsolved biological mystery.