Beneath the hot, dry grasslands of East Africa, there lives an animal whose weirdness and hardiness are legendary. The naked mole rat, a hairless rodent with a tiny, pig-like snout and nubby ears, lives in underground colonies of tunnels and nests that can stretch for miles. As many as 300 of the rodents work together in these burrows, united around a single queen, who is the only member of the colony who can reproduce. It's a hardscrabble life, with little food and even less water.
And yet in this harsh environment, under extremely crowded conditions, the naked mole rat has evolved to be virtually indestructible: these small mammals almost never get cancer, live to be over 30 (much longer than other rat species), and they are insensitive to acid burns. Now a new study in Cell Reports reveals one secret behind these rats' abilities. Evolutionary tweaks to the amino acids in their pain receptors make naked mole rats extremely insensitive to pain after they are born.
Naked mole rats probably wouldn't have evolved this incredible adaptation if it weren't for their unusual habitat and social arrangements. These rodents are one of only two mammals known to be eusocial like ants and bees—as mentioned earlier, they have one reproductive female per colony (the other eusocial mammal is also a mole rat). Females fight, often to the death, for the privilege of becoming queen and can reign for more than 15 years. Successful colonies become very large, with workers digging out tunnels and rooms with their teeth. Though their nests are big, many individuals are still crowded together in them, which no doubt causes some discomfort.
Under these conditions, the naked mole rat is likely prone to a condition called thermal hyperalgesia. Humans have the same condition, which we generally call heat sensitivity. It's what happens when your skin has already been burned or injured in some way, so an ordinary level of heat feels unbearably hot (think of running warm water over a scrape). When this happens, it's because sensory receptors on your skin have been chemically "sensitized" by inflammation or high temperatures. Once those receptors are sensitized, even a little bit of heat will cause sensory nerves to shoot signals to your brain that register as pain.
...
