The publishers of the Rejuvenation Research journal have thoughtfully started to list the fast track articles that become available online ahead of publication. I would imagine that the general trend in journals will be to move away from the existence of "issues," a bundle of publications released in one go, as publishing infrastructure becomes increasingly removed from the old school of print and paper. Looking at what's up ahead of the second the issue this year, I notice a paper by researcher Michael Rose on his SENSE thesis, a critique on the goals and methods of the Strategies for Engineered Negligible Senescence (SENS) from the perspective of his work in evolution and aging:
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.
It has to be said that I'm not on board with this way of looking at things; where it isn't a restating of the mainstream goal of re-engineering metabolism or genes to slow aging, it runs headlong and contrary into the reliability theory view of aging as damage to the machinery of the body. The various damage theories of aging are so elegant, so in sync with long-standing and proven work on the aging and breakdown of complex machinery, that postulating against them is a high wall to climb from where I stand.
Yes, you can extend life in animals through selective breeding, applying evolutionary pressure of your own. Rose has done just that in fruit flies. You can look at the biochemistry and genetics of your longer-lived animals, and plausibly reverse engineer out a longevity science from that - in much the same way as researchers are presently reverse engineering the longevity benefits of calorie restriction in mammals. But I think the critiques applied to the goal of developing metabolic manipulations to emulate calorie restriction benefits also apply to metabolic or genetic manipulation to emulate artificially selected longevity. Mainly:
- It's likely to be harder than learning to repair the metabolism we have
- It provides little or no benefit to those already old and age-damaged - it's not rejuvenation, only a slowing of existing processes