Evolving Healthy Longevity

  1. True life extension, the kind that will give us a thousand healthy years is a problem mired in complexity so many orders of magnitude deep that it's difficult to imagine, although not impossible, that we will come to the solution through merely supplement cocktails, gene therapy, regeneration/transplants etc...

    What might do the trick is the massively parallel problem solver we call evolution. By exerting a very specific evolutionary pressure, in this case "minimum age of reproduction", evenly across the entire population, and very slowly -and by slowly I mean glacially, increase the minimum age of reproduction, we can attain a truly vibrant and healthy thousand+ year lifespan for our descendants.

    This would of course be a multi-generational megaproject that would require the participation of everyone for tens if not hundreds of thousands of years. However, if this process were augmented with future breakthroughs in technologies like gene mapping and massive bio-informatics database analyses (I just pulled that one out of my backside), we could reach our goal much quicker.
    I realize the population compliance part is not feasable, but would this technically work?
     
  2. jcsd
  3. Ryan_m_b

    Staff: Mentor

    Welcome to the forums!

    There's no such thing as "true" life extension in a scientific sense, anything that increases life expectancy can count. It's worth bearing in mind that for the most part increases in life expectancy involve prevention and treatment of diseases rather than directly influencing the causal factors of aging, which are not well understood.

    Just as a cautionary note it's best not to throw around terms that don't mean anything or presuppose results like thousand year life expectancies. You have a legitimate question on how longevity can be affected by selection but please ensure your posts stay within the rules rather than wandering into overspeculation or pseudoscience.

    Technically speaking it may work, though not necessarily in the way you might expect. There have been numerous studies into longevity in fruit flies, some involve taking a new generation and discarding all eggs until only old flies are left (example of a study here). Then these eggs are taken to form a new generation and the experiment is repeated. As the paper linked reports most of this longevity is due to selection for traits that lower the chance of death from various common stresses (though I've never heard of the journal Experimental Gerontology so you might want to take it with a pinch of salt).

    I read an article a few years ago that I'll try to find when I have more time that also breed fruit flies for longevity, they found that the longer lived flies were far more docile than the control population. I don't want to say too much more without the paper to hand but I don't think this sort of observation is that surprising, it's quite likely that there would have to be some sort of trade-off. It's fairly well accepted that caloric restriction leads to longevity (see this review for more) but the obvious trade off their is a decreased diet leading to lower levels of activity and strength.

    A potential technical problem with breeding for longevity in humans is that we stop reproducing long before we reach old age. You may end up just selecting for late fertility as opposed to a form of longevity, though as in the drosophila example you might end up with longevity through resistance to various common causes of early death.
     
  4. Yes, this is what I'm thinking. You can say that evolution brackets our most healthy and productive years between birth and reproductive age. Evolution has no direct feedback after reproductive age so you don't want to extend those years. I don't think it would only end up selecting for late fertility. In a lab with a limited gene pool, yes it would be more likely to happen. But I don't propose to select for anything, rather I would apply the "minimum age of reproduction" pressure and rely on evolution to draw on the power of variety and gene recombination from the entire population. So evolution will select whatever succeeds best.
     
  5. Ryan_m_b

    Staff: Mentor

    Why not? Giving birth to a healthy child in later ages becomes increasingly difficult. Supposing for the moment that there is a strong genetic component for this then by applying a minimum age of reproduction you're going to favour the spread of genes that allow for greater fertility at a later age.

    Why not? I thought the point of this thought experiment was longevity? Increasing healthy fertile age is one thing, longevity is another. A possible modification would be to allow only very old people to reproduce using IVF which could focus the selective pressure on genotypes that favour longevity.

    I'm sorry I don't follow your reasoning. Why do you think that a limited gene pool would be more likely to select for late fertility than a larger population? A larger gene pool might grant more variety in selected traits but I don't see how it wouldn't favour later fertility like the smaller sample.
     
  6. Borek

    Staff: Mentor

  7. Yes, that is absolutely correct, and note that I wrote that I don't think it would ONLY end up selecting for late fertility. That's an obvious effect.



    Ok, then instead of envisioning a possible way to extend longevity, let's call it envisioning a possible way to increase healthy fertile age.


    Sorry, to be clear, YES, I expect later fertility in both cases. For the sake of avoiding confusion I'd like to retract the following previously posted sentence...

    "In a lab with a limited gene pool, yes it would be more likely to happen."
     
  8. Ryan_m_b

    Staff: Mentor

    Fair enough. That takes us in an interesting direction because as Borek touched on above the fact that humans aren't fertile for their entire adult lives is a bit of a mystery. It would intuitively seem that evolution would select for longer periods of fertility to increase the chances of reproduction, but this isn't the case. The grandmother hypothesis is a popular explanation, though there are other non-adaptive hypotheses such as the idea that younger mothers will be more able to defend and look after their young. Consequently there was no selective pressure to maintain fertility.

    I'm not aware of any studies looking into breeding for delayed fertility, perhaps that is something you'd like to look up. Of course with IVF there's no real need to breed for delayed fertility (again ignoring any ethical or practical objections) but it's still an interesting thought experiment related to the evolutionary explanation for menopause.
     
  9. Indeed I was aware of this but rather thought that post-menopausal longevity at least partly fed back to our genes indirectly as part of kin selection as opposed to directly through the germline.
     
  10. Ygggdrasil

    Ygggdrasil 1,569
    Science Advisor

    Here's a really cool figure from a paper studying the relationship between aging and fertility across multiple species from across the tree of life:
    [​IMG]
    Jones et al. 2014. Diversity of ageing across the tree of life. Nature 505: 169. doi:10.1038/nature12789

    Although some related species show patterns like humans (maximum fertility peaks relatively early in life before mortality increases), this pattern is by no means conserved across all species. Many show relatively constant fertility across their lifespans, and some even show decreasing mortality with increasing age. Evolutionary forces definitely do shape a species' longevity, and figuring out what selective pressures shape the fertility and mortality curves is certainly a very interesting and important question in biology.
     
    1 person likes this.
  11. That is very illuminating! It kind of takes the wind out of my sails but most appreciated none the less.
     
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