"What allows them to get to these extreme old ages is probably some protective genes that not only slow down aging, but also protect them from the bad variations," Perls said in a telephone interview. "It's almost like they are trumping the bad variants."
Perls said both participants had some genes that are widely regarded as associated with greater life spans, "but there are others that they didn't have." So it wasn't just a matter of having the right longevity genes.
"That points to just how incredibly complex this puzzle is," he said. "It involves probably hundreds of variations of hundreds of different genes, both good and bad."
Much to their dismay, scientists have found that it isn't as simple as turning a gene on or off to defeat a disease, because many genes do many things, and like all medical treatments, there can always be a downside.
It's risky to draw many conclusions from this particular study, because as Perls himself noted, two persons are not nearly enough. So many scientists at other institutions are launching broader studies in hopes unraveling this "complex puzzle" further.
What is clear at this point is that the lives of most supercentenarians are surprisingly similar. They tend to enjoy good health until very late in life, according to Perls who has been studying this for more than a decade, and their siblings also tend to lead long, healthy lives.
Many of them have serious diseases, including cancer, in their 80s or 90s, "but they handle them so much better than the general population," Perls said, possibly because good variants are controlling the bad variants, as suggested in this study.
As a result, he said, "they don't experience any disability, on average, until around the age of 93. So it's really only the last three or four years of their lives that they have any kind of age-linked disease."
Perls, who has spent a lot of time with supercentenarians, calls them "living historical treasures." Both participants, even near the end of their lives, could vividly recall the days when horse-drawn buggies fought gas-belching monsters for the right-of-way.
People in cars were always getting flat tires, the woman told him once. She said they didn't have enough sense to get a horse.