For some worm species, decapitation is no big deal — they just grow a new head.
But far from this superpower being an ancient skill, a recent study suggests that this ability is a relatively recent adaptation, at least evolutionarily speaking.
Regeneration is unusual in animals, but the species that can do it are sprinkled throughout the animal kingdom, and include sea stars, hydras, fish, frogs, salamanders and spiders, as well as worms. Regrowing body parts was long thought to be an ancient trait, with diverse animals tracing the ability to a distant shared ancestor that likely emerged hundreds of millions of years ago.
But for some species of marine ribbon worms, the capacity to regrow severed heads and brains traces back to only 10 million to 15 million years ago — making it a far more recent adaptation than previously thought, scientists found.