How long must humans live?

摘要

Species are defined by biological criteria. This characterization, however, misses the most unique aspect of our species; namely, an ability to invent technologies that reduce mortality risks. Old animals are rare in nature, but survival to old age has become commonplace in humans. Science now asks how long can humans live, but we suggest a more appropriate question is: How long must humans live? Three lines of evidence are used to identify the biological equivalent of a warranty period for humans and why it exists. The effective end of reproduction, the age when the sex ratio is unity, and the acceleration of mortality reveal that approximately 50-55 years is sufficient time for our species to achieve its biological mandate-Darwinian fitness. Identifying this boundary is biomedically important because it represents a transition from expected health and vigor to a period when health and vigor become progressively harder to maintain.