Ouroboros on the Evolution of Extreme Longevity

I pointed out a paper in passing a few weeks back, in which researchers put forward a model to explain how some species can evolve extreme longevity, or even agelessless (or negligible senescence).

How can evolution, biased to early reproductive success at all reasonable cost, produce such a species?

As it turns out, there may be some plausible scenarios - which is a good thing, given the fact that many extremely long-lived animal species exist, and that some might indeed be ageless. Problems arise for any theory that cannot explain the outliers. Chris Patil has given this work a great deal more attention over at Ouroboros, and you should take look.

The evolution of negligible senescence:

The authors describe in detail two organisms - the Bristlecone pine and Arctic quahog - that exhibit density-dependent recruitment. In both species, sessile adults live in crowded but stable conditions in which new opportunities for maturation arise rarely. In such situations, it behooves an individual organism to outlive its neighbors, so that when they die its seedlings or larvae have a place to dig in and grow up. In such contexts, the authors argue, natural selection can trigger an anti-aging arms race that results in negligible senescence as a consequence of runaway selection.

The evolution of negligible senescence, part II: Organisms that are remotely like us:

But does the evolutionary theory that explains the emergence of negligible senescence in trees and clams have anything to teach us about how long-lived species arise from short-lived stock? If so, are those lessons in any way portable to mammals? Possibly.

...

One famous example of a species with far greater longevity than similarly sized species of comparable body plan, the naked mole rat, is also territorial and eusocial. It is tempting to speculate that mole rat queens, like their peers among the harvester ants, have evolved long lifespans in order to wait out their competitors in other burrows.

...

Mole rats are no less similar to humans than lab mice are. Therefore, biogerontologists are very interested in learning the detailed mechanisms by which mole rats have delayed senescence, since it’s likely (more likely than for clams and trees, anyway) that these details might be of some practical use to us.

The most important lesson to learn from an examination of the huge range in animal - even mammal - longevity is that it is possible to design better humans with the biotechnology of tomorrow. Longer lived, less diseased, less prone to aging. That is the driving goal behind much of the mainstream work in metabolism, genetics and aging these days. It'll be a long time in the making, however - a truly massive undertaking of great scope and complexity.

While that great work is underway, we should devote more resources to the easier path to longevity: learning how to repair the humans we have now.

Comments

As a marine biologist, I was interested in your comments about arctic clam longevity. The species referenced is hermaphroditic and uncharacteristically has nonplanktotrophic larval development (many clam sp. have extended free swimming larval stages). These characteristics would seem to be the ideal genetic mechanisms - highly effective short cuts for effective extended longevity selection. I believe by comparison, it also shows the profound effects of our own genetically programed aging processes (genetically programmed senescence) that selectively favor generational adaptivity over longevity. In my opinion, until we are able to effectively change the specific genetic sequences (and especially any initial gene initiated senescence cascade process) that control our cellular senescence programs - we will see little significant increases in our ability extend the more vibrant portions of our life spans - the desired goal of increased longevity.

Posted by: duggerdm at April 7th, 2008 8:55 AM

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