I'd be interested to know more about the studies done on these people. I kind of feel studies like that often miss the point though they look at natural selection and survivor bias and a lot of other things when really all they need to look at is the facts on the ground ie these people are living longer because of their lifestyle and their environment. The physical is influenced by the psychological. They have a community, the kind of happy mutual dependency and lifelong friendship and interaction that human beings evolved for, the kind that is almost impossible to have in the modern world these days.

Also, diet of course but it intertwines with the environment and lifestyle.