[Paleopsych] Gerontology: Aubrey de Grey: The unfortunate influence of the weather on the rate of ageing
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Sat Apr 16 22:19:32 UTC 2005
The unfortunate influence of the weather on the rate of ageing:
why human caloric restriction or its emulation may only extend
life expectancy by 2-3 years.
Gerontology. 2005 Mar-Apr;51(2):73-82
de Grey AD.
Department of Genetics, University of Cambridge, Cambridge, UK.
Much research interest, and recently even commercial interest,
has been predicated on the assumption that reasonably
closely-related species--humans and mice, for example--should, in
principle, respond to ageing-retarding interventions with an
increase in maximum lifespan roughly proportional to their control
lifespan (that without the intervention). Here, it is argued that
the best-studied life-extending manipulations of mice are examples
of a category that is highly unlikely to follow this rule, and
more likely to exhibit only a similar absolute increase in maximum
lifespan from one species to the next, independent of the species'
control lifespan. That category--reduction in dietary calories or
in the organism's ability to metabolize or sense them--is widely
recognized to extend lifespan as an evolutionary adaptation to
transient starvation in the wild, a situation which alters the
organism's optimal partitioning of resources between maintenance
and reproduction. What has been generally overlooked is that the
extent of the evolutionary pressure to maintain adaptability to a
given duration of starvation varies with the frequency of that
duration, something which is--certainly for terrestrial animals and
less directly for others--determined principally by the weather.
The pattern of starvation that the weather imposes is suggested
here to be of a sort that will tend to cause all terrestrial
animals, even those as far apart phylogenetically as nematodes and
mice, to possess the ability to live a similar maximum absolute
(rather than proportional) amount longer when food is short than
when it is plentiful. This generalization is strikingly in line
with available data, leading (given the increasing implausibility
of further extending human mean but not maximum lifespan in the
industrialized world) to the biomedically and commercially sobering
conclusion that interventions which manipulate caloric intake or
its sensing are unlikely ever to confer more than 2 or 3 years'
increase in human mean or maximum lifespan at the most.
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