Naked mole rats are the superheroes of the subterranean world. The African rodent enjoys extreme longevity (up to 31 years), is resistant to cancer, feels no pain when splashed with acid or spicy hot sauce, and can go without oxygen for up to half an hour.
Of these amazing abilities, the pain insensitivity is the one that has scientists most interested. A new study from the Max Delbrück Center for Molecular Medicine in Germany reveals just how the naked mole rat remains impervious to some kinds of pain.
Specifically, the researchers looked at the phenomenon where a small skin injury—a cut, say—becomes sensitized to heat. If you cut yourself, or burn yourself, then even tepid water can feel like it burns. The naked mole rat doesn't suffer this problem because it has evolved not to. If you were spent your days digging through hard earth, without the protection of fur, and had to do it in sweltering temperatures, you too might evolve a way not to be in sever pain whenever you scratched yourself.
The research uncovered the gene responsible for the disabling of heat hyperalgesia in the naked mole rat, and the process by which it blocks the extra pain usually experienced around injured sites. But perhaps more interesting is the reason for the increased sensitivity in other mammals. When we are injured, part of the body's healing process is to load up the injury with extra pain sensors, making the area more sensitive to pain. Because this system sends signals using the same molecule that is sensitive to capsaicin—the burning chemical in peppers—it is therefore rendered much more sensitive to chilis and heat. In the naked mole rat, changes in an enzyme block this signal almost completely.
As humans who wear clothes, and rarely tunnel naked, this mutation mightn't be so useful, although there is one scenario where disabling heat hyperalgesia might benefit us: Chopping chilis with a cut finger, or putting in a contact lens after preparing Mexican food. This alone may explain why you never see a naked mole rat wearing spectacles.