Evolution of longevity in mammals.

Maximum life span is a characteristic of each species, and a diversity of maximum species life spans is seen in each mammalian order. It is argued here that different clusters of related long-lived species evolved independently. A variety of genes could have been involved such as genes for somatic maintenance and genes for resistance to causes of death, including fatal diseases. There are explanations based on natural selection for the long maximum human life span, half of which is post-reproductive.