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life span |
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life spanTime between birth and death. It ranges from a mayfly's day to certain trees' thousands of years. Its limit appears to depend on heredity, but such factors as (in humans) disease, natural disasters, war, diet, and habits such as smoking reduce it. Maximum life span is theoretical; more meaningful is average life span, which life-insurance companies and actuaries analyze and tabulate. Long-lived progenitors tend to beget long-lived descendants. A very-low-calorie diet appears to prolong life. Reduced infant mortality and improved sanitation and nutrition account for much of the increase since c. 1800—from about 35 to over 70 years in most industrialized countries. The oldest well-documented age reached by a human is 122 years. How to thank TFD for its existence? Tell a friend about us, add a link to this page, add the site to iGoogle, or visit webmaster's page for free fun content. |
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Blood levels peak in early adulthood, around age 20, and then decline greatly during the human lifespan, falling by about 80% in the elderly. In discussing the risks inherent in extending human lifespan (September/October 2004), Michael L. Culture and behavior, this example seems to suggest, are much more important to determining human lifespan than genetic endowment. |
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