What Doesn’t Kill Me Makes Me Stronger
joshmitteldorf.scienceblog.com
joshmitteldorf.scienceblog.com
> 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.
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.
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.
http://www.pnas.org/content/73/12/4604.full.pdf
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.
Any reproduction would be just creating more competition for resources if one expect to live forever. So there would be no deaths, but also no births, no mutations.
If there was no death we still would be just - what is the first life form to age? protofishes? populating the oceans until the salinity (?) changes and we were all dead.
Lets analyze the scenario where individuals don't die by aging. So we have some members of the species from generation 1 who grow up, then reproduce. In generation 2, there are some that have mutations that make them more suitable for the environment and some that make them less suitable. The less suitable ones are outcompeted and don't survive, the normal ones mostly group up to survive, and the ones with beneficial mutations outcompete all the others, leading to the deaths of some of the ones with the "original" genes, and procreate. This then happens again and again with beneficial mutations and they eventually becoming ubiquitous in the population.
There's just no way that an individual member of the species with a mutation that gives it a definite lifespan has a fitness advantage over the others, all else being equal. What's more likely is that immortality is not necessary to pass on genes, so it simply never developed because it would involve many complex systems, the individual components of which would not have conferred enough of a fitness advantage on their own to become universal in a population. And since the natural environment is harsh and predatorial, most animals don't die of old age anyway, which again limits the usefulness of an unlimited potential lifespan.
It's a philosophical quirk, but it really depends on your existential and universal (philosophies / beliefs / religions). Things you must assume, basically, in order to make meaning from what is otherwise, pure logic (structural arrangement) and pure state (instances of that structure).
The idea that aging and death are undesirable is a complex phenomena to begin with. A rock does not care that the water slowly washes it away to shape it into a new form, yet humans have very discerning opinions on the matter across all phenomena they observe. Every explanation humanity manufactures seems to have some bias.
Everything that is alive has some level of "consciousness" aka some ability to sense, detect, and adapt to it's environment. The idea that consciousness is "special" and "unqiue" is the big lie. If knowledge is unified, then that means the same is true for the universe, since what we call "knowledge" is in fact the universes structure directly. Like your hand, your car, etc. What we call "knowledge" is our representations (symbolic languages like math, english, etc). We confuse our symbols with reality.
It's not that knowledge is "provisional" (aka the structure of the universe is the truth, hence not provisional), it's that our current abstract representations of it is.
And the Demographic Theory has been validated in computer models http://mathforum.org/~josh/LogiSen-EER.pdf and http://mathforum.org/~josh/PRLS4Oikos.pdf
http://www.senescence.info/evolution_of_aging.html
http://longevity-science.org/Evolution.htm
http://en.wikipedia.org/wiki/Evolution_of_ageing
Group selection isn't as dead as you might think; I've seen it show up in a number of places in evolutionary considerations of aging over the years. But then the field of aging as a whole is very reluctant to let go of any of its hypotheses.
Insofar as there is any consensus on the evolutionary reasons for aging in multicellular organisms, it is along the lines of aging providing a necessary state of life history to provide a selection advantage in conditions of environmental change. Functionally immortal or at least negligibly senescent species clearly can exist, as there are some in the wild at present, but in near every niche that life history option has been outcompeted by aging species. Here is one expression of that idea, which again you'll see is veering into group selection:
http://arxiv.org/abs/1103.4649
"Understanding why we age is a long-lived open problem in evolutionary biology. Aging is prejudicial to the individual and evolutionary forces should prevent it, but many species show signs of senescence as individuals age. Here, I will propose a model for aging based on assumptions that are compatible with evolutionary theory: i) competition is between individuals; ii) there is some degree of locality, so quite often competition will between parents and their progeny; iii) optimal conditions are not stationary, mutation helps each species to keep competitive. When conditions change, a senescent species can drive immortal competitors to extinction. This counter-intuitive result arises from the pruning caused by the death of elder individuals. When there is change and mutation, each generation is slightly better adapted to the new conditions, but some older individuals survive by random chance. Senescence can eliminate those from the genetic pool. Even though individual selection forces always win over group selection ones, it is not exactly the individual that is selected, but its lineage. While senescence damages the individuals and has an evolutionary cost, it has a benefit of its own. It allows each lineage to adapt faster to changing conditions. We age because the world changes."
"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 http://informahealthcare.com/doi/abs/10.1080/095530006010859...
which a) has nothing to do with Hiroshima or Nagasaki, and b) found that low dose radiation in fact increased cancer risk (shock!):
"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."
"Paraquat is the chemical name for the active ingredient in Agent Orange."
In reality, paraquat is very different from the active ingredients in Agent Orange (2,4-D and 2,4,5-T).
For instance, a molecule of paraquat contains 2 nitrogen atoms and no oxygen atoms whereas a molecule of 2,4-D or 2,4,5-T contains no nitrogen and 3 oxygen atoms.
The only similarity between them that I know of is that they are both used as herbicides.
I'm an Australian who has lived the last ten years in the UK and my older Australian relatives definitely have older looking skin than my husband's UK-based family.
Plus the rate of skin cancer is definitely higher in Australia. It is a real public health issue there.
And actually, most "older people from a sunny place" you mention did not have their evolutionary roots there.
And yes, tougher and more wrinkled, but less incidence of malignant cancers (but might be because of that first item I mentioned)
"Walking around with a 40-pound backpack has the opposite effect of carrying an extra 40 pounds of belly fat."
Actually walking around with a 40-pound backpack is a bad idea, as compared to carrying the weight at the level of your belly (all other things being equal) because the risk of back damage is much higher.
Survivorship bias (or survivor bias) is a statistical artifact in applications outside finance, where studies on the remaining population are fallaciously compared with the historic average despite the survivors having unusual properties.
http://en.wikipedia.org/wiki/Survivorship_bias#As_a_general_...
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.
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.
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.
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.
This title made me think of him, I automatically appended "or paraplegic" to the title.
RIP M.
"What doesn't kill me makes me stronger."
"I hope a bus tries to make you stronger."
(source: http://thelastpsychiatrist.com/2013/09/how_does_the_shutdown...)
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.
The same reason we over complicate things. It's hard to select which direction to move in when both directions are ambiguously labeled.
“Every stress leaves an indelible scar, and the organism pays for its survival after a stressful situation by becoming a little older.” --Dr. Hans Selye
The pro-hormesis claims I've seen are highly dubious. You constantly see caloric restriction and fasting brought up. It's bunkum. Within a species the animals that eat the most live longest. The restriction idea developed from two misunderstandings: 1) If you restrict feeding early in life the growth of the animal is stunted, and within a species smaller animals live longer. 2) Lab grade animal chow is loaded with mildly toxic things like soy oil and oxidized whey protein, so eating less of it rather than more is preferable.
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.
We are like a building, but the builders never know when they are done and eventually start doing counterproductive work that destroys us.
Kicking in a response to injury or pathogen may cause cells to run programs that are less detrimental to our continued survival.
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.
Recently research on very old lady showed that all of her immune cells came from just a handful of stem cells.
It made me think that the only reason we live that long is because, that's how long our immune system lives. As we grow old it becomes less and less versatile as stem cells die out and less effective as the most effective randomly die out. Then the old age diseases kick in as there's less and less competence in cleaning up this pile of bio-matter that we are.
Excising and eating a little is not because it almost kills us and therefore it makes us stronger, just because our cleaning crew was optimized for much less food and much more movement.
Stress is not good for you. When you see pair of identical twins you can tell which one lived life of more stress. He/she looks older and by various measurements is older.
(I'm not endorsing this view - I believe aging is programmed, largely based on the fact that genes for aging have been conserved since the dawn of eukaryotic life, i.e., cells that have a cell nucleus.)
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?
In every case, the answer is "young".
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).
Creatures that do not have a trainable nervous system (trees, coral, insects) experience a very different aging process.
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.
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?
Humans are often not so well-fed, at least not nutritionally.
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"?
Would love to hear the opinion of doctors/scientists on this...
Put simply, you can't just jump from looking at individual survival to looking at a group's survival, because any individual could just be a free-rider. More importantly, what's actually been observed is that group selectionism simply doesn't happen in the real world.
So while anything I said about the rest would be mere opinion, there is at least one multi-paragraph section of his argument that is a GIANT heap of shit.
Eat less food and get more exercise.
Hormesis is about dose. In these cases, the dose is just too high and our body is unable to cope with it.
In my case the damage is just below this threshold and my body has created a powerful antioxidant machinery [1] that is keeping me alive. In other cases of my disease, the burden - % of mutant mitochondria - is just too high [2] and sadly, the kids die when they are 3-4 years old.
[1] http://www.sciencedirect.com/science/article/pii/S1096719203...
Aging isn't there because our genes "need" it. It's there because our genes don't need 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.
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).
Mild stressors that would occur naturally - physical exertion, exposure, hunger; it is perfectly logical that natural selection would favour those who handle these circumstances well.
I have a (an emotional) problem with that number though, being acutely aware and sensitive to ageism or age-related relegation of human functions and roles in society. I have a problem with any number for that matter. 50 is too low, and any number will always be too low, the way I see it if you incorporate Dawkins' idea of the Selfish Gene into the mix. I would argue that sticking around "to ensure the survival of our offspring" (as you put it) for the human species is significantly more important than any other species on the planet.
Turtles don't need this survival strategy. Lay eggs (procreate) and chuck - that form of hormesis aggressively weeds out the weak members of the species from the ones laying eggs for the next generation. While chimps, elephants and whales may also need to "stick around longer" for their young - relatively, the human is by far an incredible outlier in this regard. Not only do adults have to stick around for their kids well into the young's teen years, but elders too have to stick around for the group or for the clan. This last point is important to understand the relationship between the survival success of the species and an imagined age cutoff for "usefulness" (that contributes to the success of the species) of any one member of the species. The individual has extended roles beyond just his/her offspring. His/her role in the clan's survival success mattered too.
Recent discoveries of hominid fossils suggest that as early as Erectus, "humans" have been keeping their elders alive! :-) Evidence of a toothless skulls suggest that able members of the group may have been keeping the elder alive by chewing for her. But for what?? Could it be to access knowledge of poisoned berries to avoid, or hunting methods to teach or ... stay at home creche for the kids while able-bodied adults went out for hunting??
Again, I don't think I needed to respond to your point necessarily ... you're right for the most part.
I see what you mean, but with every generation of your offspring, you're less and less vital to their survival - your children and grandchildren can care for your great-grandchildren as well; there's more redundancy there, so no individual is as crucial.
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]
No it's not! 3 out of the 7 links relate to homeopathy, which the article explicitly states is problematic:
'Association with the problematic science of homeopathy. In the early 20th Century, people who promoted homeopathic medicine were prominent supporters of the concepts of hormesis.'
Your stance is based on an argumentum ab auctoritate. How about constructing an argument, rather than spewing meta-trash talk?
> a word I first learned in the latest book by Nassim Nicholas Taleb, who is not a person with medical training or experience
Ergo, hormesis does not exist? Non sequitur.
> 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.
The only prescription of the article was to eat less & exercise more!
> Thank you to the several commenters who have already politely pointed out factual and logical mistakes in this submission.
Agreed. It's called 'discussion'.
> "Essentially there are two rules here: don't post or upvote crap links, and don't be rude or dumb in comment threads."
I don't see how this quote is relevant.