“It’s a phenomenon where many things go right at the same time. These people retain their cognitive functions until the end of their lives. They do not have cardiovascular disease. Parkinson’s disease is totally absent,” said Sebastiana. “When you see many genes involved, even if we have variants that are common in the population, you have to have them all at the same time. That becomes very, very rare.”

Think of it like a lottery where you need to get a hundred or a thousand numbers correct. It’s not hard to get a few right, but getting them all is remarkably improbable. (Also, you have to not get hit by a bus or killed in a war while you wait to see if you won.)