Making SENSE: strategies for engineering negligible senescence evolutionarily

Thirty years ago, in 1977, few biologists thought that it would be possible to increase the maximum life span characteristic of each species over the variety of environmental conditions in which they live, whether in nature or in the laboratory. But the evolutionary theory of aging suggested otherwise. Accordingly, experiments were performed with fruit flies, Drosophila melanogaster, which showed that manipulation of the forces of natural selection over a number of generations could substantially slow the rate of aging, both demographically and physiologically. After this first transgression of the supposedly absolute limits to life extension, it was suggested that mammals too could be experimentally evolved to have greater life spans and slower aging. And further, it was argued that such postponed-aging mammals could be used to reverse-engineer a slowing of human aging. The subsequent discovery and theoretical explanation of mortality-rate plateaus revealed that aging was not due to the progressive physiological accumulation of damage. Instead, aging is now understood by evolutionary biologists to arise from a transient fall in age-specific adaptation, a fall that does not necessarily proceed toward ineluctable death. This implies that SENS must be based on re-tuning adaptation, not repairing damage. As evolutionary manipulation of model organisms shows us how adaptation can be focused on engineering negligible senescence, there are thus both scientific and practical reasons for making SENS evolutionary; that is making SENSE.