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Tradeoff-free longevity?

I'm working on my talk for the Applied Evolution Summit, so don't have time to write a detailed post, but here are some papers that looked interesting, with brief comments on some of them:

Amino-acid imbalance explains extension of lifespan by dietary restriction in Drosophila
(published in Nature by Richard Grandison, Matthew Piper & Linda Partridge)
Dietary restriction reduces reproduction and increases longevity in many species. This study, using fruit-flies, showed that adding the amino acid, methionine, to a restricted diet restored total lifetime reproduction to that of fully-fed flies, but with the greater longevity of restricted-diet flies. Extrapolating to humans, the paper suggests that

the benefits of dietary restriction for health and lifespan may be obtained without impaired fecundity

But, if there would be no reproductive cost to doing so, why haven't flies evolved the ability to discard the "extra" food they get when fully-fed -- except for the methionine -- and live longer? I suspect that the restricted-plus-methionine diet affects the timing of reproduction, but data on timing weren't reported. (Instead, they give an "index of lifetime fecundity.") If overall population size is increasing (as fully-fed flies might expect), individuals that reproduce earlier make a disproportionate contribution to the gene pool. So the evolutionary trade-off may be between longevity and earliness of reproduction, not total reproduction. If population is decreasing, however, individuals who delay reproduction make a larger contribution to the gene pool, as laid out in our "shrinking pool" hypothesis. My guess is that flies respond to the restricted-plus-methionine diet as a cue predicting population decline and reproduce later, thereby gaining the observed increase in longevity. Extrapolating to humans again, we might be able to develop diets or other treatments that increase life-span and health, but which cost us teenage pregnancy. Hmmm... might be worth it.

Click "aging" at right for other posts relevant to this topic.

Regulating Alternative Lifestyles in Entomopathogenic Bacteria

Mozambican Grass Seed Consumption During the Middle Stone Age
If our ancestors were eating grass seeds 100,000 years ago, as this paper seems to show, what kind of selection, inadvertent or perhaps deliberate, were they imposing on those grasses?

Phylogeographic reconstruction of a bacterial species with high levels of lateral gene transfer

On the Origin of Species by Natural and Sexual Selection


Coots use hatch order to learn to recognize and reject conspecific brood parasitic chicks
"When experimentally provided with the wrong reference chicks, coots can be induced to discriminate against their own offspring"

Increasing phylogenetic resolution at low taxonomic levels using massively parallel sequencing of chloroplast genomes

Have giant lobelias evolved several times independently? Life form shifts and historical biogeography of the cosmopolitan and highly diverse subfamily Lobelioideae (Campanulaceae)
DNA analysis suggests that giant Lobelias evolved once and then spread, even to remote places like Hawaii, rather than evolving separately in different locations.

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