History and prospects: symposium on organisms with slow aging

We discuss the background concepts which lead to this issue of Experimental Gerontology. On one hand, genetic and molecular studies of short-lived wor ms, flies, and mice are yielding remark able discoveries on gene systems th at regulate the life span. On the other hand, little is known about the nat ure of aging in other vertebrates, with life spans extending into the human range or beyond the record 122 y human life span, which may have aging pro cesses that are so slow as to be 'negligible'. We point out that organisms with these vastly different life spans have essentially identical cells wit hin an evolutionary group and that the cellular tool kit that existed by 60 0 million years ago allowed the evolution of life spans ranging up to one m illion-fold difference in length. The possibility of negligible senescence has not been widely discussed, and may be in conflict with mathematical ded uctions from population genetics theory. We propose minimal criteria for th e lack of senescence: (1) no observable increase in age-specific;mortality rate or decrease in reproduction rate after sexual maturity; and (2) no obs ervable age-related decline in physiological capacity or disease resistance . We also introduce some of the species discussed in subsequent chapters wh ich are unfamiliar models to most biomedical researchers. (C) 2001 Elsevier Science Inc. All rights reserved.