How to Grow A New Head

Regeneration of body parts can be very useful, a trick of nature's that even the ancients contemplated. In Greek mythology, Hercules faced a formidable foe—the eight-headed Lernaean Hydra.

Whenever Hercules would lop off one of the Hydra's heads, the beast would simply grow two new ones. (Finally Hercules burnt out the Hydra's head "roots" with firebrands, which did the creature in.)

 

Real life offers its own comparable conjuring feats. Consider that some lizards can grow back sliced-off tails. When grabbed by the leg at a certain point, such as by a hungry snapping turtle, crayfish can move a special muscle and break off part of the limb, which it'll regenerate later. Crayfish can also regrow pincers and claws. Frog tadpoles can accomplish something similar, by regrowing lost rudimentary limbs. Frogs lose the ability as they get older, however, so you can't have your French Frog Leg Casserole and your healthy live pet frog too.

Earthworms are the real Houdinis when it comes to part regeneration, though. Made up of segments, earthworms can regrow either a new head or a new tail, depending on where the severing took place. For example, let's say you are gardening and you accidentally push your hoe right down on an unsuspecting worm. If you cut off around 20 of the head-end segments, the rest of the worm will grow back a head, but only stuck onto 5 or so newly formed segments. In essence, you've just created a dwarf worm.

Recently, MIT researchers made an interesting discovery about heads or tails regeneration in worms. They studied planarian flatworms, which are common, freshwater-dwelling worms. After some experimentation, they identified a gene called Smed-beta-catenin-1 that's involved in the process. By inhibiting this gene, the scientists made the chopped up flatworm grow a new head instead of a tail. A rather freaky consequence of the experiments was that some of the worms wound up with heads at both ends. It's believed that the gene is therefore active across different parts of the worm, but is inhibited by the regulated expression of this, and possibly other, genes.

Now here's what's really freaky. Humans, as well as jellyfish and many animals, possess genes that are very similar to the worm's "heads or tail"  gene.  Frogs and sea urchins use these same genes when forming their posterior tissue. Of course all of this research is in its relative infancy, but regenerating human body parts could certainly solve a lot of health problems. Somewhere, out in the Scottish Highlands, Mel Gibson's William Wallace could still be screaming, "Freedom!"