I'm not buying the Demographic Theory of Senescence.<p>> Aging is nature’s way of leveling out the death rate, assuring that we don’t all die at the same time. Aging puts our deaths on an individual schedule so we can die at different times; other causes of death tend to kill everyone or no one.<p>It's a magical "group selection" hand-wavy argument—it sounds nice and is kind of heart-warming, but when making an evolutionary argument, that's usually a bad sign. In this case, it doesn't provide an explanation of how purposeful aging could possibly increase an individual's probability of passing on their genes.<p>If not aging was an option, you would expect to see something more similar to the results of Michael J. Wade's 1976 experimental attempt to show group selection behavior in individuals of a species. He artificially induced resource constraints on a selected subpopulation of flour beetles to see if the beetles would restrain their reproduction for the benefit of the group. What happened? The adults started eating the young of the other adult beetles.<p><a href="http://www.pnas.org/content/73/12/4604.full.pdf" rel="nofollow">http://www.pnas.org/content/73/12/4604.full.pdf</a><p>I don't have an explanation for aging, but I seriously doubt that it's a way for Nature to regulate population size to avoid resource depletion for the group.
There are some questionable assertions in this article. eg,<p>"Survivors of the Hiroshima and Nagasaki bombings had lower cancer rates later in life than people of similar age who had not been exposed to radiation " has the ref <a href="http://informahealthcare.com/doi/abs/10.1080/09553000601085980" rel="nofollow">http://informahealthcare.com/doi/abs/10.1080/095530006010859...</a><p>which a) has nothing to do with Hiroshima or Nagasaki, and b) found that low dose radiation in fact increased cancer risk (shock!):<p>"The results suggest that prolonged low dose-rate radiation exposure appeared to increase risks of developing certain cancers in specific subgroups of this population in Taiwan."
Mitteldorf has an interesting take on programmed aging, which is to say the collection of theories suggesting aging is a evolved program that acts to shorten life because there is some very global selection advantage in it. It is worth reading as a counterpoint to the more common viewpoints of that school (such as the hyperfunction theory of aging that is a modern take on antagonistic pleiotropy in the context of programmed aging) espoused by some of the Russian gerontology community. There's a link somewhere in the article linked above.<p>Programmed aging is, however, a minority view in the aging research community as a whole. The consensus view is that aging is caused by an accumulation of unrepaired damage, though there are many factions and a lot of debate within that tent. Programmed aging seems to be gaining some ground, but it's rather hard to tell from the sidelines as some of the advocates (e.g. Blagosklonny and his views on mTOR) are very prolific in their publications.<p>Hormesis as a phenomenon to be measured and evaluated can stand apart from either of these views on aging for the purposes of evaluation and investigation of molecular mechanisms. It is a robustly demonstrated thing in animal models, though as for all these things translating those findings into human health is ever a challenge. For things like calorie restriction, exercise, and intermittent fasting, where hormesis is thought to play an important role, the human and rodent responses in the short term are very similar. There is a small mountain of papers on this topic - just go look at PubMed and search for hormesis and longevity.<p>Hormesis works because some forms of damage - such as mild oxidative stress - trigger repair responses that last long enough and are proficient enough to produce a net benefit in cell health throughout tissues. There is a dose-response curve to all of this of course. This is may be how you get a variety longevity mutants in nematode worms wherein they live longer if you either reduce or increase the flux of reactive oxygen species emitted from the mitochondria. Less means less damage and more means less damage because it produces more aggressive repair.<p>There are plenty of ways to damage tissue that will cause incremental damage over time, but are not hormetic, and will not produce benefits. It all depends on how the repair mechanisms handle the specific case in question.
I had a friend who was telling everybody : "what doesn't kill you makes you stronger ... or paraplegic" and it made him laugh every time.<p>This title made me think of him, I automatically appended "or paraplegic" to the title.<p>RIP M.
I'm sure your sources are correct but the view and sample data are biased. Cancer rates, as you note, go up with radiation and also withUV exposure. You make a dangerous point that some people who don't read carefully might buy into fast and make poor decision. A warning at the top of the post or another analysis of the effects of these exposures, on a large sample that also presents the downsides would be more balanced.
Hormesis as a general concept reeks of me of the "like cures like" of Homeopathy. This is mentioned in the article even. "A little snake venom is a cure to snake venom" is commonly used when explaining homeopathy. There may be some scenarios that exhibit this behavior but it still means your relaying on a fallacy of composition to turn it into something that can be sold as a life style.<p>Why do we have to simplify things and try to apply sweeping generalizations? The universe is complex. Things that apply one way to somethings do not apply that way to others.
A lot of this makes sense in the new deterministic model of aging.<p>It argues that aging is not a collection of mutations, the old/popular model, but instead a programmed outcome of our genes that never experienced selective pressure.<p>We are like a building, but the builders never know when they are done and eventually start doing counterproductive work that destroys us.<p>Kicking in a response to injury or pathogen may cause cells to run programs that are less detrimental to our continued survival.<p>Edit: Let me clarify that this in no way should be taken as an endorsement of the author's claims. I have proposed a possible model that would make the claims reasonable, but haven't examined them closely. There is a lot of quackery out there.
I think aging, in vertebrates, is mostly driven by the need to preserve what data has been encoded in the nervous system.<p>Ask yourself these questions. Would you rather have old bones or young bones? Would you rather have an old cardio-vascular system or a young cardio-vascular system? Would you rather have old muscles or young muscles?<p>In every case, the answer is "young".<p>But would you rather have an old nervous system or a young nervous system? The old nervous system is trained, the young one lacks all skills (skills range from the basics, like control of urination and defecation, to knowing how to hunt down an antelope).<p>Creatures that do not have a trainable nervous system (trees, coral, insects) experience a very different aging process.<p>Among vertebrates, those creatures that demonstrate negligible senescence (tortoises) also demonstrate a lack of learning. The price of immortality is perpetual immaturity of one's nervous system.
Sounds like a wind up for one of Garry Trudeau's characters from back in the day...<p><a href="http://en.wikipedia.org/wiki/Mr._Butts" rel="nofollow">http://en.wikipedia.org/wiki/Mr._Butts</a>
To quote Dobzhansky, this is all becomes obvious in the light of evolution. A challenging environment removes those cells that accumulate mutations. (i) In challenging or resource constrained environments mutated cells tend to behave more aberrantly and our immune system responds by attacking them (this is why radiation therapy works). (ii) Mutated cells will be more prone to pathogenic infection. In either case, we use the external world as a kind of extended immune system or to police our bodies against cellular mutiny.
>If animals eat all the food that is available to them and reproduce as fast is they are physically capable, then the environment will be denuded, the next generation will starve, and the species will face extinction. All animal species are evolved to avoid this<p>Isn't this a Tragedy of the Commons? Won't genes that cause individuals to eat more and reproduce more quickly than fellow members of their species confer a relative advantage causing those genes to spread through the gene pool?
This is all based on the ability of the organism to strongly adapt. In order to do this, they need enough energy (calories) and micronutrients. I assume the organisms studied in labs for the ability to adapt to these stressors, are (outside of calorie restriction or related studies) well-fed...<p>Humans are often not so well-fed, at least not nutritionally.
A very interesting concept, will definitely need to read more on this!<p>But what about the kind of research that talks about the dangers of living in cities... like "living in a polluted city is like smoking X cigarettes a day"?
This sounds a lot like Taleb's Antifragile:
<a href="http://en.wikipedia.org/wiki/Antifragile" rel="nofollow">http://en.wikipedia.org/wiki/Antifragile</a>
If this is true... then I need to rethink a lot of my life choices... what is actually good for me?<p>Would love to hear the opinion of doctors/scientists on this...
Yeah... what about bacteriocidal antibiotics that cause mitochondrial DNA damage? The people affected by that stuff don't seem to just like recover and get stronger.
I'm very skeptical.<p>Aging isn't there because our genes "need" it. It's there because our genes <i>don't need</i> long lifespans. The gain in reproductive viability that we'd get with a >60 year natural lifespan just isn't enough to justify the constraint that a much longer (or indefinite) lifespan would impose on our genetic "search space". We can live forever and be simple, or we can be complex and get a job done and die.<p>There probably is some anti-fragility in us. I don't buy the LNT threshold of radiation, for example. All that said, I'm not sure that hormesis is useful as a general concept. There are mild stressors (such as cold, when prepared and for short duration) that turn out to have positive effects, but there are a great number of stressors that seem to have no positive effects, whether you're talking about biological agents (e.g. cadmium, lead) or psychological experiences (e.g. rape, war).
Searching for articles with the keyword "hormesis" (a word I first learned in the latest book by Nassim Nicholas Taleb, who is not a person with medical training or experience) on the Science-Based Medicine website is instructive.[1] The concept of "hormesis" is not well thought out enough or well validated enough with careful measurements to be your guide to your personal health practices. There is better health advice in some of the earlier comments here.<p>Thank you to the several commenters who have already politely pointed out factual and logical mistakes in this submission. We can do better for reading matter to be submitted to Hacker News. "Essentially there are two rules here: don't post or upvote crap links, and don't be rude or dumb in comment threads."[2]<p>[1] <a href="http://www.sciencebasedmedicine.org/?s=hormesis" rel="nofollow">http://www.sciencebasedmedicine.org/?s=hormesis</a><p>[2] <a href="https://news.ycombinator.com/newswelcome.html" rel="nofollow">https://news.ycombinator.com/newswelcome.html</a>