Stephen Friend never thought he’d go looking for superheroes.

“The idea came from frustration and unfulfilled quests,” says Friend, a physician at the Icahn School of Medicine at Mount Sinai. For decades, he had watched geneticists trying to find the genes that underlie diseases as diverse as cystic fibrosis, Alzheimer’s disease, and schizophrenia. Such studies have been undoubtedly successful, but the growing list of culprit genes have rarely led to treatments for their respective disorders.

“I had an a-ha moment,” says Friend. “If you want to find a way of preventing disease, you shouldn’t be looking at people with the disease. “You should look at people who should have been sick but aren’t.”

These people, unbeknownst to them, carry genes that all but guarantee that they’ll get fatal diseases. And yet, somehow, they’re completely healthy. They might carry other genes that mitigate their risk. Or perhaps, some aspect of their diet, lifestyle, or environment shields them from their harmful inheritance. Either way, Friend reasoned that if he could find these “genetic superheroes”, and work out the secrets of their powers, he could find ways of helping others to beat the odds.