This article is about the few humans who reach very old ages--here called "longevity outliers." They are a distinct group, with lower mortality rates than most of the population. Centenarians are human longevity outliers. They are more resistant to causes of death such as heart disease and cancer than those who die at younger ages. Inheritance of life span, the present condition of centenarians, and their causes of death are considered. The maximum human life span in the future will be affected, at least marginally, as more longevity outliers survive to challenge today's maximum of 121 years.