ABOVE: Highveld mole rats are indifferent to several chemicals that cause pain in other animals—an advantage when rooming with an aggressive ant species.
DEWALD KLEYNHANS, UNIVERSITY OF PRETORIA
Pain, unpleasant though it may be, is essential to most mammals’ survival, a warning to back off before we lose a limb or worsen a wound. So it was curious when, in a 2008 study, molecular physiologist Gary Lewin and his colleagues found that, unlike most mammals, naked mole rats (Heterocephalus glaber) didn’t lick or flick a limb that had been injected with a small amount of capsaicin—the hot in hot chili pepper. The mole rats turned out to be similarly nonchalant when exposed to dilute hydrochloric acid. “We wondered, first of all, how they became insensitive to these things,” says Lewin, who heads up a lab at Berlin’s Max Delbrück Center for Molecular Medicine.
The team took an evolutionary approach to finding ...
