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Massive genetic study shows how humans are evolving

323 points by gwern 9y ago

ronnier 9y ago
* Analysis of 215,000 people's DNA suggests variants that shorten life are being selected against. * tested more than 8 million common mutations, and found two that seemed to become less prevalent with age. A variant of the APOE gene, which is strongly linked to Alzheimer’s disease, was rarely found in women over 70. And a mutation in the CHRNA3 gene associated with heavy smoking in men petered out in the population starting in middle age. People without these mutations have a survival edge and are more likely to live longer, the researchers suggest. * certain groups of genetic mutations, which individually would not have a measurable effect but together accounted for health threats, appeared less often in people who were expected to have long lifespans than in those who weren't. These included predispositions to asthma, high body mass index and high cholesterol. * Most surprising, however, was the finding that sets of mutations that delay puberty and childbearing are more prevalent in long-lived people.
- deleted 9y ago
  [deleted]
- mannykannot 9y ago
  This puzzled me, as these Alzeheimer's and smoking results do not seem to be evidence of evolution; one would surely need to see a decrease over generations? The article goes on to say 'That such a large study found only two [late-acting genes] strongly suggests that evolution is “weeding” them out, says Mostafavi, and that others have probably already been purged from the population by natural selection.' The article and paper then repeat some hypotheses as to why natural selection would eliminate these hypothesized former late-acting genes from the gene pool, given that they seem to act after most people's reproductive years. So the article and paper seem to be arguing that a low frequency of late-acting genes indicates ongoing evolution, but acknowledge that this raises questions about why natural selection would act on them. The relevance of the decrease of the prevalence of these genes with age is apparently that survivorship bias is being used to distinguish causation from mere correlation.
  - perlgeek 9y ago
    I had the same reaction as you at first, but read carefully: "Mostafavi and his colleagues tested more than 8 million common mutations, and found two that seemed to become less prevalent with age" Old people are less likely to have this gene than young people. This can have two possible explanations: old people with this gene are more likely to are already dead (and thus not show up in the study), or the gene is becoming more prevalent in the younger generations. The statement "People without these mutations have a survival edge and are more likely to live longer" favors the first explanation. This is not the effect of natural selection on gene prevalence. (And it would be weird for Alzheimer's, which usually occurs at an age where reproduction is often finished, and maybe even raising the kids is done already).
    - mannykannot 9y ago
      My apologies for editing my reply to add a third paragraph while you were replying to it, but I think that explains the relevance of the age dependence to this study: the decrease in the prevalence with age suggests that they actually do exacerbate the diseases they are associated with, and so the association is not merely a correlation. Note that they are not suggesting these genes have been the subject of selection; it is the hypothesized number of such late-acting genes that were not found that are assumed to have been selected against.
  - memeCrasher 9y ago
    Could be that the genes have a deleterious effect in youth, not just old age.
    - mannykannot 9y ago
      That is one of the hypotheses advanced in the article.
    - AlexCoventry 9y ago
      Or it could be that aging is a complex process which a naive experiment like this is unlikely to shed much light on.
- EGreg 9y ago
  That last one may have a great deal to do with it. As people live longer and safer lives, they can afford to have children later. And child mortality has been seriously reduced, so the children they have are comparable to thise among people from previous centuries who had many children younger. Having children takes a toll on an organism, and having many children takes a larger toll, presumably. I wouldn't be surprised if there is a correlation between lifespan and number of children, among women. So - people live longer and have children later. The children grow up richer and bigger and in turn have children later, as well. I bet there is a correlation between age of having children and lifespan.
  - tomerbd 9y ago
    there is i tell you ;) at least 20 years less off your life.
  - glenstein 9y ago
    I definitely think postponing reproduction would coincide with longevity, but for a completely different/same-but-differently-stated reason. Evolution doesn't seem to care very much about the survival of an organism once they've successfully reproduced an optimal number of offspring, except to the extent that the organism can see to the well-being of offspring. It stands to reason that postponing reproduction for as long as reasonably possible would contribute to selection for longevity. From evolution's perspective, you have to survive at least that long, or else you're not good for anything. If humanity collectively decides to postpone having children, evolution may begrudgingly allocate more of its resources toward the welfare of individuals, rather than viewing our early deaths as an acceptable loss in a cold utilitarian calculation about long-term gene proliferation. (edits)
    - EGreg 9y ago
      Very interesting! I find this kind of line very exciting. But dows that mean some sort of Lamarckian evolution is taking place after all? Sexy son hypothesis is also similar. Is it related?
    - ForRealsies 9y ago
- trophycase 9y ago
  The last point isn't surprising at all. I think there is a subset of the population that matures quickly, reproduces quickly, and dies quickly. From my own observations in middle school and high school, those that mature earlier are far more likely to get into drugs, forgo education, etc... all things that are measures of success in our current society
  - xtreme 9y ago
    Success in our society is not a good measure of evolutionary success. Evolution is only concerned about the number of viable offsprings you produce, not how well off they are.
    - wernercd 9y ago
      For reference, see Idiocracy opening sequence... https://www.youtube.com/watch?v=YwZ0ZUy7P3E https://www.youtube.com/watch?v=YwZ0ZUy7P3E Smart people delay, wait and then end up not... "dumb" people just hook up and go to town... I think the fact that Evolution is still spreading "successful" genes and "unsuccessful" genes become less prevalent is obvious. What isn't obvious, is as Idiocracy so succinctly puts it, is that gene that are "successful" doesn't necessarily translate to intelligence, good decisions, stable lifestyle, etc.
      - robotresearcher 9y ago
        That successful genes spread is a tautology. The frequency of a gene in a population compared to its alleles is its success. I wish we could retire the idea of success in an evolution and just talk about gene frequency. Then the irrelevant ideas of goodness and progress don't come up so readily in people's minds.
marcelsalathe 9y ago
Direct link to paper (OA): http://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.2002458 http://journals.plos.org/plosbiology/article?id=10.1371/jour...
Will_Parker 9y ago
Now that we have access to the entire genome directly, instead of relying on twin and adoption studies, we are going to get many more of these insights. And it's not all going to be comfortable. There will be cries of biological essentialism, while the blank slate idea is no longer one that can be held by an educated rational person. On more controversial lines, see this http://www.biorxiv.org/content/early/2017/09/06/184853.1 http://www.biorxiv.org/content/early/2017/09/06/184853.1 study (N=280,000) that correlates specific genes with IQ.
- adrianN 9y ago
  I wonder how long it will take until some enterprising society will start a new eugenic breeding program, this round with a faster feedback loop. It could start as simple as extra tax breaks for desireable genotypes if they have children, or tax reductions for undesireables if they get long-term birth control. Already in you can reduce prison sentences by voluntary sterilization in Tennessee.
  - 0xfeba 9y ago
    IIRC, China is trying to do just that.
  - PrimalDual 9y ago
    I am probably being naive but I see nothing wrong with the examples you listed. Isn't this how iceland essentially erradicated downs syndrome? Using information about genetics to inform how we steer the populations' gene pool sounds very good to me.
  - Will_Parker 9y ago
    It doesn't even need to be breeding, it could be CRISPR technology. How close is that to the mass market? To some parents it could be very defensible as technology to fix a child's genetic defect, which was preventing longer life or peak brain function.
    - adrianN 9y ago
NyxWulf 9y ago
I agree with the premise, these reports seem to focus on the act of passing your genetic material to a child as the final act. Anyone who has had kids knows that passing on your genes is the easy part, raising them to be productive members of society who will in turn procreate takes a long time and you continue to influence and guide them. So something that shortens your lifespan would reduce the survival edge of the remaining offspring compared to a group with that guiding influence. This is a pretty clear social structure in humans. I understand not all or even most animals have that same social structure. Can someone explain to me why they would assume remaining alive after you dump off your genetic material would be neutral? (from an evolutionary perspective)
- tempestn 9y ago
  This is addressed in the article: Why these late-acting mutations might lower a person’s genetic fitness — their ability to reproduce and spread their genes — remains an open question. The authors suggest that for men, it could be that those who live longer can have more children, but this is unlikely to be the whole story. So scientists are considering two other explanations for why longevity is important. First, parents surviving into old age in good health can care for their children and grandchildren, increasing the later generations’ chances of surviving and reproducing. This is sometimes known as the ‘grandmother hypothesis’, and may explain why humans tend to live long after menopause.
riazrizvi 9y ago
I found the article confusing, I don't understand the link between the paper and evolution: 1. APOE-Alzheimer-propensity gene is a new gene, emerging in the younger population. (Clearly, prevalence of this gene reduces a person's life-expectancy but not until they are done giving birth). 2. Same with CHRNA3-heavy-smoking-propensity gene. 3. These genes are not evolutionary drivers since they don't effect E[number of offspring] or E[survival rate until given birth to final offspring]. 4. From an evolutionary perspective, prevalence of these genes should be found in equal proportion across all ages of the population. 5. Then why are these genes emerging? Isn't it far more likely that there is some new factor in our lifestyle/diet/habitat etc that is causing the gene to appear in the population? Which has nothing to do with evolution. Where in the paper do they talk about evolution?
- perlgeek 9y ago
  The confusing part is that we are used to thinking about evolution as spanning multiple generations: a gene increases fitness, so its prevalence increases over the generations. Or the flip side: it decreases fitness, so the members that have it reproduce less, its prevalence decreases. But this study takes a snapshot of a population, and looks at gene prevalence as a function of age. So what you see are not effects of reproduction, but rather on survival. It finds the Alzheimer's gene less in 70 year olds, because those with the gene are more likely to have died earlier, and thus not appear in the study. Thus your statement "APOE-Alzheimer-propensity gene is a new gene" is likely not true. It is likely just as prevalent in the current generation as two generations before; just those individuals from two generations before who had it are more likely to be already dead. So the study looks at how genes influence survival rates -- something that is very obviously related to evolution if it occurs before reproduction. If survival rates only depend on some genes in higher age, they have only small, second-order effects on reproduction (like a child being more likely to survive if it has healthy grandparents or parents). (Disclaimer: I'm not a biologist, so take this with a grain of salt).
  - Udik 9y ago
    > It finds the Alzheimer's gene less in 70 year olds, because those with the gene are more likely to have died earlier, and thus not appear in the study. So wouldn't the study be: "Those carrying genetic disease have a tendency to die early(er)"? What does evolution have to do with it? BTW, it's perfectly possible for a gene to be wildly successful from the evolutionary point of view, while at the same time killing its owner invariably by the age of 50. How would this study have classified such a gene?
cowpig 9y ago
> But if that were the case, there would be plenty of such mutations still kicking around in the genome, the authors argue. That such a large study found only two strongly suggests that evolution is “weeding” them out, says Mostafavi, and that others have probably already been purged from the population by natural selection. This seems like a lot of speculative leaps to me. 1. assuming that they should necessarily find many of these correlations, absent evolutionary elimination (maybe the effects of individual groups of genes just aren't that strong?) 2. assuming that the lack of them indicates that they existed before and were eliminated (maybe they never existed at all?) 3. more generally, assuming that evolutionary selection is a determining factor in the data they're studying at all (I don't often see noticeable changes in a few generation in highly-contrived genetic algorithms I play with, let alone real-world data which has way, way more noise)
Udik 9y ago
Can someone explain this to me? The article says: "People who carry a harmful genetic variant die at a higher rate, so the variant becomes rarer in the older portion of the population." However, this is the opposite of how I understand evolution: "harmful" variants (from the evolutionary point of view) should become rarer in the younger portion of the population- whatever happens to their original carriers is irrelevant. Also "researchers scoured large US and UK genetic databases"- well, I wouldn't be too sure that the biggest part of evolution happening in the human species can be seen inside the UK and US genetic databases.
joak 9y ago
An explanation not explored in the paper: the social pressure to have children later in life favors people living older.
hellofunk 9y ago
> one of the first attempts to probe directly how humans are evolving over one or two generations. Considering the extraordinary amount of time it takes for evolution to do anything at all, that they can quantify it in what is relatively zero time in the span of life on Earth, seems to remarkable to be true.
- tempestn 9y ago
  It takes a long time for the changes to be obviously observable. But at least some change has to occur in any given generation, in order for it to build up to 'significant' change over time. So now that we can look at genes directly, it makes sense that we would potentially be able to identify these changes.
  - hellofunk 9y ago
    > But at least some change has to occur in any given generation This is not usually true and not typically how many species have evolved. Typically a long sequence of generations will exist with zero change, and then individual evolutionary events occur to create very rapid change in a very short period of time before stabilizing with long periods of no change again. A lot of people here are expressing what they seem to think evolution is without apparently having ever actually studied it; that is my take-away anyway.
    - tempestn 9y ago
      Interesting. I'm unfamiliar with that position, but as you say, I'm certainly not an expert in the area. A bit of googling didn't turn up evidence one way or the other; do you happen to have a reference?
      - hellofunk 9y ago
        My main reference is what I was taught in an animal behavior course several years ago at university. There are some interesting books on this subject on my reading list, but I haven't yet gotten to them.
c3534l 9y ago
I'm confused about how the inferences are being made. If genes are found in older people, okay, so what? That doesn't mean anything. But then the article says: > But if that were the case, there would be plenty of such mutations still kicking around in the genome. So does that mean the gene is less common in children than parents? If so, what does it matter that older people don't have the gene? Why does age factor into this at all?
randyrand 9y ago
we're evolving mostly through sexual selection now as opposed to natural selection but still some of that too
- sacado2 9y ago
  What's the difference between sexual & natural selection ?
  - randyrand 9y ago
    Sexual selection can still happen even if humans become immortal. Natural selection cannot.
meri_dian 9y ago
This study absolutely does not show that humans are evolving
- pamqzl 9y ago
  Unless the statistical distribution of alleles is exactly the same (unlikely) from one generation to the next then humans would have to be evolving, wouldn't they?
  - gwern 9y ago
    Genetic drift is not usually considered 'evolving' because the variants are selectively neutral. That's why finding selected variants isn't as simple as 'SNP X is 0.00001% more common in generation 2 than generation 1, case closed!' - you are looking for variants which are becoming more/less frequent than would be plausible under simple drift. Just like an experiment where you know the effect will never be exactly 0 because of chance imbalances and random noise.
- loblollyboy 9y ago
  yeah - a gene that kills you is less common in people over the age that it tends to kill you? SHOCKER! Also, super high testosterone dudes probably inseminate more women than betas and they probably die younger too.
LinuxFreedom 9y ago
You do not even need a scientist to see that there is a massive degeneration and retardation going on in the US gene pool currently. Influx of foreign genes was the solution, but now dumbness itself will trigger its own growth even stronger. If you want a better gene pool for your descendants it is time to leave US now. Good Luck!
- sctb 9y ago
  This comment is way outside the standards of civility and substantiveness here. We ban accounts that continue to post like this. https://news.ycombinator.com/newsguidelines.html https://news.ycombinator.com/newsguidelines.html
marcofloriano 9y ago
* This is not, by itself, evidence of evolution at work. In evolutionary terms, having a long life isn’t as important as having a reproductively fruitful one, with many children who survive into adulthood and birth their own offspring. So harmful mutations that exert their effects after reproductive age could be expected to be ‘neutral’ in the eyes of evolution, and not selected against. This. We want to live more (and more). But that's not the main point of life, as science (and most religions) say. We are in our best form when we reproduce and give our best to our children (and family). So they can do the same in the future. Today's society tries to sell the idea of small families (or no family at all ) and long lives as the best option. But maybe it's not the case.
subru 9y ago
This reminds me of my core mission: sterilize myself or self terminate. Everything I've experienced and felt since youth indicates that my seed is unwanted by humanity, and it's clear suicide helps evolution by eliminating bad genes. I think about suicide constantly and have done so since youth. This is my brain telling me to help humanity by leaving. Hoping to complete that mission ASAP.
- jmmcd 9y ago
  I wouldn't necessarily go along with your logic here. If you decide not to have children for one reason or another you can implement that decision without suicide. A lot of people have suicidal thoughts at some stages in their lives, then recover and are glad they didn't take a non-reversible action. Anyway, it's too dangerous a topic for you to work things out without a bit of "peer review". So I strongly recommend to contact a counsellor.
  - subru 9y ago
    This isn't occurring st some subset of stages; it's been steady throughout my entire life. And I've grown more and more cynical with age. It's a decision that I've long intellectualized. People who don't survive aren't around anymore to discuss whether they are satisfied with their decision. Why would I waste my time talking to someone who intends to talk me out of something that isn't a debate to me? It's a personal decision.
    - magic_beans 9y ago
      Have you considered Buddhism, the entire purpose of which is to learn to overcome suffering? Here's a summary: http://www.bcc.ca/buddhism/fournobletruthsandeightfoldpath.html http://www.bcc.ca/buddhism/fournobletruthsandeightfoldpath.h...
- sacado2 9y ago
  Suicide doesn't help evolution. If you have bad genes, you die before you can reproduce, or your children do. If you and your children survive, those were good genes. You don't have to do anything to manage evolution, it takes care of itself by its own.
jlebrech 9y ago
People are having children later on in life so it would make sense.
otakucode 9y ago
It is odd that longer lifespans would be selected for. Given two otherwise equivalent populations, the one with the shorter lifespan will come to dominate.
- 24gttghh 9y ago
  This does not seem intuitive to me. Would not having a longer lifespan allow a subset of a population to better care for itself through social means?

323 points by gwern 9y ago

* Analysis of 215,000 people's DNA suggests variants that shorten life are being selected against. * tested more than 8 million common mutations, and found two that seemed to become less prevalent with age. A variant of the APOE gene, which is strongly linked to Alzheimer’s disease, was rarely found in women over 70. And a mutation in the CHRNA3 gene associated with heavy smoking in men petered out in the population starting in middle age. People without these mutations have a survival edge and are more likely to live longer, the researchers suggest. * certain groups of genetic mutations, which individually would not have a measurable effect but together accounted for health threats, appeared less often in people who were expected to have long lifespans than in those who weren't. These included predispositions to asthma, high body mass index and high cholesterol. * Most surprising, however, was the finding that sets of mutations that delay puberty and childbearing are more prevalent in long-lived people.

deleted 9y ago
[deleted]
mannykannot 9y ago
This puzzled me, as these Alzeheimer's and smoking results do not seem to be evidence of evolution; one would surely need to see a decrease over generations? The article goes on to say 'That such a large study found only two [late-acting genes] strongly suggests that evolution is “weeding” them out, says Mostafavi, and that others have probably already been purged from the population by natural selection.' The article and paper then repeat some hypotheses as to why natural selection would eliminate these hypothesized former late-acting genes from the gene pool, given that they seem to act after most people's reproductive years. So the article and paper seem to be arguing that a low frequency of late-acting genes indicates ongoing evolution, but acknowledge that this raises questions about why natural selection would act on them. The relevance of the decrease of the prevalence of these genes with age is apparently that survivorship bias is being used to distinguish causation from mere correlation.
- perlgeek 9y ago
  I had the same reaction as you at first, but read carefully: "Mostafavi and his colleagues tested more than 8 million common mutations, and found two that seemed to become less prevalent with age" Old people are less likely to have this gene than young people. This can have two possible explanations: old people with this gene are more likely to are already dead (and thus not show up in the study), or the gene is becoming more prevalent in the younger generations. The statement "People without these mutations have a survival edge and are more likely to live longer" favors the first explanation. This is not the effect of natural selection on gene prevalence. (And it would be weird for Alzheimer's, which usually occurs at an age where reproduction is often finished, and maybe even raising the kids is done already).
  - mannykannot 9y ago
    My apologies for editing my reply to add a third paragraph while you were replying to it, but I think that explains the relevance of the age dependence to this study: the decrease in the prevalence with age suggests that they actually do exacerbate the diseases they are associated with, and so the association is not merely a correlation. Note that they are not suggesting these genes have been the subject of selection; it is the hypothesized number of such late-acting genes that were not found that are assumed to have been selected against.
- memeCrasher 9y ago
  Could be that the genes have a deleterious effect in youth, not just old age.
  - mannykannot 9y ago
    That is one of the hypotheses advanced in the article.
  - AlexCoventry 9y ago
    Or it could be that aging is a complex process which a naive experiment like this is unlikely to shed much light on.
EGreg 9y ago
That last one may have a great deal to do with it. As people live longer and safer lives, they can afford to have children later. And child mortality has been seriously reduced, so the children they have are comparable to thise among people from previous centuries who had many children younger. Having children takes a toll on an organism, and having many children takes a larger toll, presumably. I wouldn't be surprised if there is a correlation between lifespan and number of children, among women. So - people live longer and have children later. The children grow up richer and bigger and in turn have children later, as well. I bet there is a correlation between age of having children and lifespan.
- tomerbd 9y ago
  there is i tell you ;) at least 20 years less off your life.
- glenstein 9y ago
  I definitely think postponing reproduction would coincide with longevity, but for a completely different/same-but-differently-stated reason. Evolution doesn't seem to care very much about the survival of an organism once they've successfully reproduced an optimal number of offspring, except to the extent that the organism can see to the well-being of offspring. It stands to reason that postponing reproduction for as long as reasonably possible would contribute to selection for longevity. From evolution's perspective, you have to survive at least that long, or else you're not good for anything. If humanity collectively decides to postpone having children, evolution may begrudgingly allocate more of its resources toward the welfare of individuals, rather than viewing our early deaths as an acceptable loss in a cold utilitarian calculation about long-term gene proliferation. (edits)
  - EGreg 9y ago
    Very interesting! I find this kind of line very exciting. But dows that mean some sort of Lamarckian evolution is taking place after all? Sexy son hypothesis is also similar. Is it related?
  - ForRealsies 9y ago
trophycase 9y ago
The last point isn't surprising at all. I think there is a subset of the population that matures quickly, reproduces quickly, and dies quickly. From my own observations in middle school and high school, those that mature earlier are far more likely to get into drugs, forgo education, etc... all things that are measures of success in our current society
- xtreme 9y ago
  Success in our society is not a good measure of evolutionary success. Evolution is only concerned about the number of viable offsprings you produce, not how well off they are.
  - wernercd 9y ago
    For reference, see Idiocracy opening sequence... https://www.youtube.com/watch?v=YwZ0ZUy7P3E https://www.youtube.com/watch?v=YwZ0ZUy7P3E Smart people delay, wait and then end up not... "dumb" people just hook up and go to town... I think the fact that Evolution is still spreading "successful" genes and "unsuccessful" genes become less prevalent is obvious. What isn't obvious, is as Idiocracy so succinctly puts it, is that gene that are "successful" doesn't necessarily translate to intelligence, good decisions, stable lifestyle, etc.
    - robotresearcher 9y ago
      That successful genes spread is a tautology. The frequency of a gene in a population compared to its alleles is its success. I wish we could retire the idea of success in an evolution and just talk about gene frequency. Then the irrelevant ideas of goodness and progress don't come up so readily in people's minds.

marcelsalathe 9y ago

Direct link to paper (OA): http://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.2002458 http://journals.plos.org/plosbiology/article?id=10.1371/jour...

Will_Parker 9y ago

Now that we have access to the entire genome directly, instead of relying on twin and adoption studies, we are going to get many more of these insights. And it's not all going to be comfortable. There will be cries of biological essentialism, while the blank slate idea is no longer one that can be held by an educated rational person. On more controversial lines, see this http://www.biorxiv.org/content/early/2017/09/06/184853.1 http://www.biorxiv.org/content/early/2017/09/06/184853.1 study (N=280,000) that correlates specific genes with IQ.

adrianN 9y ago
I wonder how long it will take until some enterprising society will start a new eugenic breeding program, this round with a faster feedback loop. It could start as simple as extra tax breaks for desireable genotypes if they have children, or tax reductions for undesireables if they get long-term birth control. Already in you can reduce prison sentences by voluntary sterilization in Tennessee.
- 0xfeba 9y ago
  IIRC, China is trying to do just that.
- PrimalDual 9y ago
  I am probably being naive but I see nothing wrong with the examples you listed. Isn't this how iceland essentially erradicated downs syndrome? Using information about genetics to inform how we steer the populations' gene pool sounds very good to me.
- Will_Parker 9y ago
  It doesn't even need to be breeding, it could be CRISPR technology. How close is that to the mass market? To some parents it could be very defensible as technology to fix a child's genetic defect, which was preventing longer life or peak brain function.
  - adrianN 9y ago

NyxWulf 9y ago

I agree with the premise, these reports seem to focus on the act of passing your genetic material to a child as the final act. Anyone who has had kids knows that passing on your genes is the easy part, raising them to be productive members of society who will in turn procreate takes a long time and you continue to influence and guide them. So something that shortens your lifespan would reduce the survival edge of the remaining offspring compared to a group with that guiding influence. This is a pretty clear social structure in humans. I understand not all or even most animals have that same social structure. Can someone explain to me why they would assume remaining alive after you dump off your genetic material would be neutral? (from an evolutionary perspective)

tempestn 9y ago
This is addressed in the article: Why these late-acting mutations might lower a person’s genetic fitness — their ability to reproduce and spread their genes — remains an open question. The authors suggest that for men, it could be that those who live longer can have more children, but this is unlikely to be the whole story. So scientists are considering two other explanations for why longevity is important. First, parents surviving into old age in good health can care for their children and grandchildren, increasing the later generations’ chances of surviving and reproducing. This is sometimes known as the ‘grandmother hypothesis’, and may explain why humans tend to live long after menopause.

riazrizvi 9y ago

I found the article confusing, I don't understand the link between the paper and evolution: 1. APOE-Alzheimer-propensity gene is a new gene, emerging in the younger population. (Clearly, prevalence of this gene reduces a person's life-expectancy but not until they are done giving birth). 2. Same with CHRNA3-heavy-smoking-propensity gene. 3. These genes are not evolutionary drivers since they don't effect E[number of offspring] or E[survival rate until given birth to final offspring]. 4. From an evolutionary perspective, prevalence of these genes should be found in equal proportion across all ages of the population. 5. Then why are these genes emerging? Isn't it far more likely that there is some new factor in our lifestyle/diet/habitat etc that is causing the gene to appear in the population? Which has nothing to do with evolution. Where in the paper do they talk about evolution?

perlgeek 9y ago
The confusing part is that we are used to thinking about evolution as spanning multiple generations: a gene increases fitness, so its prevalence increases over the generations. Or the flip side: it decreases fitness, so the members that have it reproduce less, its prevalence decreases. But this study takes a snapshot of a population, and looks at gene prevalence as a function of age. So what you see are not effects of reproduction, but rather on survival. It finds the Alzheimer's gene less in 70 year olds, because those with the gene are more likely to have died earlier, and thus not appear in the study. Thus your statement "APOE-Alzheimer-propensity gene is a new gene" is likely not true. It is likely just as prevalent in the current generation as two generations before; just those individuals from two generations before who had it are more likely to be already dead. So the study looks at how genes influence survival rates -- something that is very obviously related to evolution if it occurs before reproduction. If survival rates only depend on some genes in higher age, they have only small, second-order effects on reproduction (like a child being more likely to survive if it has healthy grandparents or parents). (Disclaimer: I'm not a biologist, so take this with a grain of salt).
- Udik 9y ago
  > It finds the Alzheimer's gene less in 70 year olds, because those with the gene are more likely to have died earlier, and thus not appear in the study. So wouldn't the study be: "Those carrying genetic disease have a tendency to die early(er)"? What does evolution have to do with it? BTW, it's perfectly possible for a gene to be wildly successful from the evolutionary point of view, while at the same time killing its owner invariably by the age of 50. How would this study have classified such a gene?

cowpig 9y ago

> But if that were the case, there would be plenty of such mutations still kicking around in the genome, the authors argue. That such a large study found only two strongly suggests that evolution is “weeding” them out, says Mostafavi, and that others have probably already been purged from the population by natural selection. This seems like a lot of speculative leaps to me. 1. assuming that they should necessarily find many of these correlations, absent evolutionary elimination (maybe the effects of individual groups of genes just aren't that strong?) 2. assuming that the lack of them indicates that they existed before and were eliminated (maybe they never existed at all?) 3. more generally, assuming that evolutionary selection is a determining factor in the data they're studying at all (I don't often see noticeable changes in a few generation in highly-contrived genetic algorithms I play with, let alone real-world data which has way, way more noise)

Udik 9y ago

Can someone explain this to me? The article says: "People who carry a harmful genetic variant die at a higher rate, so the variant becomes rarer in the older portion of the population." However, this is the opposite of how I understand evolution: "harmful" variants (from the evolutionary point of view) should become rarer in the younger portion of the population- whatever happens to their original carriers is irrelevant. Also "researchers scoured large US and UK genetic databases"- well, I wouldn't be too sure that the biggest part of evolution happening in the human species can be seen inside the UK and US genetic databases.

joak 9y ago

An explanation not explored in the paper: the social pressure to have children later in life favors people living older.

hellofunk 9y ago

> one of the first attempts to probe directly how humans are evolving over one or two generations. Considering the extraordinary amount of time it takes for evolution to do anything at all, that they can quantify it in what is relatively zero time in the span of life on Earth, seems to remarkable to be true.

tempestn 9y ago
It takes a long time for the changes to be obviously observable. But at least some change has to occur in any given generation, in order for it to build up to 'significant' change over time. So now that we can look at genes directly, it makes sense that we would potentially be able to identify these changes.
- hellofunk 9y ago
  > But at least some change has to occur in any given generation This is not usually true and not typically how many species have evolved. Typically a long sequence of generations will exist with zero change, and then individual evolutionary events occur to create very rapid change in a very short period of time before stabilizing with long periods of no change again. A lot of people here are expressing what they seem to think evolution is without apparently having ever actually studied it; that is my take-away anyway.
  - tempestn 9y ago
    Interesting. I'm unfamiliar with that position, but as you say, I'm certainly not an expert in the area. A bit of googling didn't turn up evidence one way or the other; do you happen to have a reference?
    - hellofunk 9y ago
      My main reference is what I was taught in an animal behavior course several years ago at university. There are some interesting books on this subject on my reading list, but I haven't yet gotten to them.

c3534l 9y ago

I'm confused about how the inferences are being made. If genes are found in older people, okay, so what? That doesn't mean anything. But then the article says: > But if that were the case, there would be plenty of such mutations still kicking around in the genome. So does that mean the gene is less common in children than parents? If so, what does it matter that older people don't have the gene? Why does age factor into this at all?

randyrand 9y ago

we're evolving mostly through sexual selection now as opposed to natural selection but still some of that too

sacado2 9y ago
What's the difference between sexual & natural selection ?
- randyrand 9y ago
  Sexual selection can still happen even if humans become immortal. Natural selection cannot.

meri_dian 9y ago

This study absolutely does not show that humans are evolving

pamqzl 9y ago
Unless the statistical distribution of alleles is exactly the same (unlikely) from one generation to the next then humans would have to be evolving, wouldn't they?
- gwern 9y ago
  Genetic drift is not usually considered 'evolving' because the variants are selectively neutral. That's why finding selected variants isn't as simple as 'SNP X is 0.00001% more common in generation 2 than generation 1, case closed!' - you are looking for variants which are becoming more/less frequent than would be plausible under simple drift. Just like an experiment where you know the effect will never be exactly 0 because of chance imbalances and random noise.
loblollyboy 9y ago
yeah - a gene that kills you is less common in people over the age that it tends to kill you? SHOCKER! Also, super high testosterone dudes probably inseminate more women than betas and they probably die younger too.

LinuxFreedom 9y ago

You do not even need a scientist to see that there is a massive degeneration and retardation going on in the US gene pool currently. Influx of foreign genes was the solution, but now dumbness itself will trigger its own growth even stronger. If you want a better gene pool for your descendants it is time to leave US now. Good Luck!

sctb 9y ago
This comment is way outside the standards of civility and substantiveness here. We ban accounts that continue to post like this. https://news.ycombinator.com/newsguidelines.html https://news.ycombinator.com/newsguidelines.html

marcofloriano 9y ago

* This is not, by itself, evidence of evolution at work. In evolutionary terms, having a long life isn’t as important as having a reproductively fruitful one, with many children who survive into adulthood and birth their own offspring. So harmful mutations that exert their effects after reproductive age could be expected to be ‘neutral’ in the eyes of evolution, and not selected against. This. We want to live more (and more). But that's not the main point of life, as science (and most religions) say. We are in our best form when we reproduce and give our best to our children (and family). So they can do the same in the future. Today's society tries to sell the idea of small families (or no family at all ) and long lives as the best option. But maybe it's not the case.

subru 9y ago

This reminds me of my core mission: sterilize myself or self terminate. Everything I've experienced and felt since youth indicates that my seed is unwanted by humanity, and it's clear suicide helps evolution by eliminating bad genes. I think about suicide constantly and have done so since youth. This is my brain telling me to help humanity by leaving. Hoping to complete that mission ASAP.

jmmcd 9y ago
I wouldn't necessarily go along with your logic here. If you decide not to have children for one reason or another you can implement that decision without suicide. A lot of people have suicidal thoughts at some stages in their lives, then recover and are glad they didn't take a non-reversible action. Anyway, it's too dangerous a topic for you to work things out without a bit of "peer review". So I strongly recommend to contact a counsellor.
- subru 9y ago
  This isn't occurring st some subset of stages; it's been steady throughout my entire life. And I've grown more and more cynical with age. It's a decision that I've long intellectualized. People who don't survive aren't around anymore to discuss whether they are satisfied with their decision. Why would I waste my time talking to someone who intends to talk me out of something that isn't a debate to me? It's a personal decision.
  - magic_beans 9y ago
    Have you considered Buddhism, the entire purpose of which is to learn to overcome suffering? Here's a summary: http://www.bcc.ca/buddhism/fournobletruthsandeightfoldpath.html http://www.bcc.ca/buddhism/fournobletruthsandeightfoldpath.h...
sacado2 9y ago
Suicide doesn't help evolution. If you have bad genes, you die before you can reproduce, or your children do. If you and your children survive, those were good genes. You don't have to do anything to manage evolution, it takes care of itself by its own.

jlebrech 9y ago

People are having children later on in life so it would make sense.

otakucode 9y ago

It is odd that longer lifespans would be selected for. Given two otherwise equivalent populations, the one with the shorter lifespan will come to dominate.

24gttghh 9y ago
This does not seem intuitive to me. Would not having a longer lifespan allow a subset of a population to better care for itself through social means?