5 ms·

> 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 ev

> 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.
mannykannot 9y ago
The natural time period of evolution is the generation; meaningful change must occur over that sort of period, or it is not going to happen at all. Evolution is going on all the time; it's just the major effects, such as the establishment of a new family, that usually takes a long time (I say 'establishment' over 'emergence', as talking about the time for emergence runs into the sorites (you have to draw a line somewhere) problem.)
- hellofunk 9y ago
  > The natural time period of evolution is the generation; meaningful change must occur over that sort of period Unless you have specific education in this area, this is contrary to the classes I took in university on the topic of animal biology. There is no "natural time period" for evolution, as you say. Meaningful change usually does not happen over any arbitrary period. It is typically a random event that spikes rarely in a species, and usually there are long periods of zero change until such spikes occur between these changes. I suspect you are postulating on what evolution is without actually knowing how it most often emerges.
  - mannykannot 9y ago
    Firstly, a matter of terminology: my use of 'natural period' may be wrong here, if it implies a cyclical process; I am not sure what might be the correct term, so I shall use 'characteristic period'. You are confusing two different but related issues, and may have misunderstood your professor. The timing of large effects (speciation, for example) is unpredictable, and there are long periods in the history of any given line of descent during which no speciation-level evolution occurred (note that the article is about evolution at a much smaller scale than speciation. These events are unpredictable in detail, but occur much more frequently.) As for the process by which it happens - variation and natural selection - the generation is, to a first approximation, a characteristic unit of time. A mutation occurs at a point in time, but it is only subject to being selected by natural selection if and when it is passed in the next generation, and natural selection works by creating more of the next generation on account of it. This is somewhat complicated by the appearance of neutral mutations, which do not have effects that are selected for or against. These take the genome on a continual but evolutionarily directionless random walk, for which the characteristic time period is the generation. There is the possibility that, as a consequence of these random walks, any given allele's frequency in the population will drop to zero, after which it will not reappear unless it is recreated by another mutation. While neutral mutations, by definition, have no evolutionary effect at their inception, they may become significant either as a consequence of a change in the environment or through the allele's interaction with, or modification by, a subsequent mutation. Whenever that happens, however, natural selection still works by changing the occurrence of the allele from one generation to the next. On reflection, my phrase "meaningful change must occur over that sort of period, or it is not going to happen at all" is inaccurate; to express what I was thinking, I would now write that "when evolution occurs, it is manifest from one generation to the next." I see that you are aware that evolution has a tendency to occur in spikes, so it seems odd that you would write, in your initial post, "Considering the extraordinary amount of time it takes for evolution to do anything at all..." There is no requirement for there to be long periods of stasis between events.
vanderZwan 9y ago
This is a very, very stubborn idea about evolution that has proven to be kind of false. Rapid evolution exists, and we can observe evolution happening in many species: http://discovermagazine.com/2015/march/19-life-in-the-fast-lane http://discovermagazine.com/2015/march/19-life-in-the-fast-l... As I understand, the simplest explanation for species being so stable over millions of years (like, say, sharks) is that while evolution can happen quite fast, it "averages itself out" - there's a kind of regression-to-the-mean effect.
- hellofunk 9y ago
  I have been taught something different in school, but that was a while ago, so perhaps the field has evolved some in recent years. That, depending on the species, evolution rarely occurs between generations, and that it leans on large changes that are sudden and far between, and these changes are not at the same time for each species. That is to say, evolution is not usually a linear process for which at any point in time there is a delta. It is more of a stair step. That is part of what makes the report hard to believe, even if it is a novel idea and has some other merits. Not to say it couldn't be true, but as I expressed, it seems remarkable that such evidence was found in a single generational study.
  - vanderZwan 9y ago
    You're right that it is a relatively recent development: the first papers (cautiously) going against this idea of evolution happening slowly started appearing in the middle of the last century. The first paper flat-out stating evolution was observed within a few generations was in the late 1970s (mentioned in the linked article in my previous post). So you can imagine it would take a while for the field to accept this new attitude, let alone how long it takes for this new knowledge to then diffuse into the rest of society. Either way my comment certainly wasn't intended as a critique aimed at you! Also, thinking about it some more, it's not that strange that the idea of slow evolution hasn't died out yet, because it's not so much wrong as that reality more complicated and really counter-intuitive than what you think if you only look at fossils[0]: > In the 1950s, the Finnish biologist Björn Kurtén noticed something unusual in the fossilized horses he was studying. When he compared the shapes of the bones of species separated by only a few generations, he could detect lots of small but significant changes. Horse species separated by millions of years, however, showed far fewer differences in their morphology. Subsequent studies over the next half century found similar effects — organisms appeared to evolve more quickly when biologists tracked them over shorter timescales. > Then, in the mid-2000s, Simon Ho, an evolutionary biologist at the University of Sydney, encountered a similar phenomenon in the genomes he was analyzing. When he calculated how quickly DNA mutations accumulated in birds and primates over just a few thousand years, Ho found the genomes chock-full of small mutations. This indicated a briskly ticking evolutionary clock. But when he zoomed out and compared DNA sequences separated by millions of years, he found something very different. The evolutionary clock had slowed to a crawl. (I have to apologise for not remembering this article yesterday, it would have made things more clear) So in retrospect my "very stubborn idea" assessment is probably a bit unfair. But, back to what we were taught in school. Caveat: I'm not a biologist, let alone evolution expert, just a nerd who is into this topic. There are a number of issues with the description you gave (which, for the record, fits with how it was taught to me in high-school) It is true that evolution is not linear, but being taught that evolution is a stair step is just as bad. It (implicitly) assumes evolution is a form of progress. It's not, it's just adaptation. The simplest of life forms that exist nowadays are just as successful as we are, in the sense that they also didn't go extinct and will continue to thrive in the future. On the other end of the spectrum you actually can have runaway adaptation, especially when there's a kind of "arms race" between predator and prey. The cheetah is so hyper-specialised for catching its prey by speed alone that it's a kind of evolutionary dead-end; it can't zig-zag like the gazelle can. Anyway, the stair-step attitude originates from outside of biology, from Platonic thinking that there are "higher" ideal forms. And the sudden changes turn out not to be "few and far between", they just don't seem to stick. Most adaptations average out, because they're highly contextual to their short time periods. As mentioned, since we based our first ideas about evolution on fossils, we only noticed the slow evolution. Sex actually seems to play a large part in the filtering process[1]: > For a species whose numbers show no signs of collapsing, humans have a shockingly high mutation rate. Each of us is born with about 70 new genetic errors that our parents did not have. That’s much more than a slime mold, say, or a bacterium. Mutations are likely to decrease an organism’s fitness, and an avalanche like this every generation could be deadly to our species. The fact that we haven’t gone extinct suggests that over the long term, we have some way of taking out our genetic garbage. And a new paper, recently published in Science, provides evidence that the answer may be linked to another fascinating procedure: sex. (...) As the number of nasty genetic errors in a population rises, natural selection will sweep large rafts of them out of the genome together. And in sexual organisms, because of the ways that mutations from each parent can recombine randomly onto the same chromosomes, the synergistic elimination of bad mutations can happen even faster. Anyway, hope this addresses some of your understandable scepticism! [0] https://www.quantamagazine.org/evolution-runs-faster-on-short-timescales-20170314/ https://www.quantamagazine.org/evolution-runs-faster-on-shor... [1] https://www.quantamagazine.org/missing-mutations-suggest-a-reason-for-sex-20170713/ https://www.quantamagazine.org/missing-mutations-suggest-a-r...
rxhernandez 9y ago
I mean, I'm assuming these people are professional biologists of some sort, that have probably spent decades in their field. Not only that but they would know more about how evolution works than the average college educated layperson. I'm a little frustrated to point that out. However my frustration isn't enough to motivate my next question. What did you hope to accomplish, in light of these problems, by criticizing these scientists' work with what is ostensibly, cursory popular science knowledge? I guess I just want to understand why there is a mistrust for professional scientists even on a site as technologically inclined as HN.
- hellofunk 9y ago
  > I guess I just want to understand why there is a mistrust for professional scientists even on a site as technologically inclined as HN. I think you are new to HN. There is a long history of healthy skepticism by the readers here of studies posted in a wide range of fields. Healthy skepticism, or at least, pointing out remarkable and hard-to-believe aspects of a reported study (as I did here), is quite commonplace all over HN. In fact, if you read any of the nearly hundred other comments in this thread, you will see equal amounts of skepticism, some more verbose, some more terse, than what I expressed. Fortunately, you did not go and criticize those commenters also. In the case of evolution, I was taught years ago in school that evolution is not a gradual and linear process, and that often very long stretches occur with zero evolutionary action, then a single evolutionary event causes a gigantic leap of changes in a species, a single spike, which then plateaus again for a long time another spike. I am not an evolutionary scientist of course, but I was leaning on that, and layman's perception of evolution, in my comment. I'm frustrated to have to point this out. What did you hope to accomplish by criticising my reaction to the article? Are we not all here to comment on our opinions and reactions to the items posted? Just because you do not agree with my particular reaction to the article does not mean you should make such wide assumptions about my own motivations (or those of any other reader you choose to attack in the future).
haihaibye 9y ago
Imagine a conception occurs with a random mutation that causes a miscarriage. That's evolution in a few months. Imagine one that causes someone to be infertile. The balance of genetics changes (evolution) in a generation. Africa went from 1/2 the population of Europe in 1950 to 1.6x the size today. The gene frequencies on those two continents are different - thus there has clearly been differential fitness (in the hundreds of millions in a lifetime)
- hellofunk 9y ago
  > That's evolution in a few months. A single isolated event with no impact on the species is not the definition that most would use for evolution. And even if it had an effect on that individual family, evolution is about nature selecting that particular mutation, which may not happen at all. So I don't support the premise of your argument.
  - haihaibye 9y ago
    Evolution is the change in gene frequencies over time. Accepting my premise is just knowing the textbook definition. I think what you are trying to describe is "novel fitness increasing mutations" - these won't be detectable for ages as it takes time to spread through a population. Single isolated events matter - All mutations start off in an individual, they then increase or decrease in frequency.

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.

mannykannot 9y ago

The natural time period of evolution is the generation; meaningful change must occur over that sort of period, or it is not going to happen at all. Evolution is going on all the time; it's just the major effects, such as the establishment of a new family, that usually takes a long time (I say 'establishment' over 'emergence', as talking about the time for emergence runs into the sorites (you have to draw a line somewhere) problem.)

hellofunk 9y ago
> The natural time period of evolution is the generation; meaningful change must occur over that sort of period Unless you have specific education in this area, this is contrary to the classes I took in university on the topic of animal biology. There is no "natural time period" for evolution, as you say. Meaningful change usually does not happen over any arbitrary period. It is typically a random event that spikes rarely in a species, and usually there are long periods of zero change until such spikes occur between these changes. I suspect you are postulating on what evolution is without actually knowing how it most often emerges.
- mannykannot 9y ago
  Firstly, a matter of terminology: my use of 'natural period' may be wrong here, if it implies a cyclical process; I am not sure what might be the correct term, so I shall use 'characteristic period'. You are confusing two different but related issues, and may have misunderstood your professor. The timing of large effects (speciation, for example) is unpredictable, and there are long periods in the history of any given line of descent during which no speciation-level evolution occurred (note that the article is about evolution at a much smaller scale than speciation. These events are unpredictable in detail, but occur much more frequently.) As for the process by which it happens - variation and natural selection - the generation is, to a first approximation, a characteristic unit of time. A mutation occurs at a point in time, but it is only subject to being selected by natural selection if and when it is passed in the next generation, and natural selection works by creating more of the next generation on account of it. This is somewhat complicated by the appearance of neutral mutations, which do not have effects that are selected for or against. These take the genome on a continual but evolutionarily directionless random walk, for which the characteristic time period is the generation. There is the possibility that, as a consequence of these random walks, any given allele's frequency in the population will drop to zero, after which it will not reappear unless it is recreated by another mutation. While neutral mutations, by definition, have no evolutionary effect at their inception, they may become significant either as a consequence of a change in the environment or through the allele's interaction with, or modification by, a subsequent mutation. Whenever that happens, however, natural selection still works by changing the occurrence of the allele from one generation to the next. On reflection, my phrase "meaningful change must occur over that sort of period, or it is not going to happen at all" is inaccurate; to express what I was thinking, I would now write that "when evolution occurs, it is manifest from one generation to the next." I see that you are aware that evolution has a tendency to occur in spikes, so it seems odd that you would write, in your initial post, "Considering the extraordinary amount of time it takes for evolution to do anything at all..." There is no requirement for there to be long periods of stasis between events.

vanderZwan 9y ago

This is a very, very stubborn idea about evolution that has proven to be kind of false. Rapid evolution exists, and we can observe evolution happening in many species: http://discovermagazine.com/2015/march/19-life-in-the-fast-lane http://discovermagazine.com/2015/march/19-life-in-the-fast-l... As I understand, the simplest explanation for species being so stable over millions of years (like, say, sharks) is that while evolution can happen quite fast, it "averages itself out" - there's a kind of regression-to-the-mean effect.

hellofunk 9y ago
I have been taught something different in school, but that was a while ago, so perhaps the field has evolved some in recent years. That, depending on the species, evolution rarely occurs between generations, and that it leans on large changes that are sudden and far between, and these changes are not at the same time for each species. That is to say, evolution is not usually a linear process for which at any point in time there is a delta. It is more of a stair step. That is part of what makes the report hard to believe, even if it is a novel idea and has some other merits. Not to say it couldn't be true, but as I expressed, it seems remarkable that such evidence was found in a single generational study.
- vanderZwan 9y ago
  You're right that it is a relatively recent development: the first papers (cautiously) going against this idea of evolution happening slowly started appearing in the middle of the last century. The first paper flat-out stating evolution was observed within a few generations was in the late 1970s (mentioned in the linked article in my previous post). So you can imagine it would take a while for the field to accept this new attitude, let alone how long it takes for this new knowledge to then diffuse into the rest of society. Either way my comment certainly wasn't intended as a critique aimed at you! Also, thinking about it some more, it's not that strange that the idea of slow evolution hasn't died out yet, because it's not so much wrong as that reality more complicated and really counter-intuitive than what you think if you only look at fossils[0]: > In the 1950s, the Finnish biologist Björn Kurtén noticed something unusual in the fossilized horses he was studying. When he compared the shapes of the bones of species separated by only a few generations, he could detect lots of small but significant changes. Horse species separated by millions of years, however, showed far fewer differences in their morphology. Subsequent studies over the next half century found similar effects — organisms appeared to evolve more quickly when biologists tracked them over shorter timescales. > Then, in the mid-2000s, Simon Ho, an evolutionary biologist at the University of Sydney, encountered a similar phenomenon in the genomes he was analyzing. When he calculated how quickly DNA mutations accumulated in birds and primates over just a few thousand years, Ho found the genomes chock-full of small mutations. This indicated a briskly ticking evolutionary clock. But when he zoomed out and compared DNA sequences separated by millions of years, he found something very different. The evolutionary clock had slowed to a crawl. (I have to apologise for not remembering this article yesterday, it would have made things more clear) So in retrospect my "very stubborn idea" assessment is probably a bit unfair. But, back to what we were taught in school. Caveat: I'm not a biologist, let alone evolution expert, just a nerd who is into this topic. There are a number of issues with the description you gave (which, for the record, fits with how it was taught to me in high-school) It is true that evolution is not linear, but being taught that evolution is a stair step is just as bad. It (implicitly) assumes evolution is a form of progress. It's not, it's just adaptation. The simplest of life forms that exist nowadays are just as successful as we are, in the sense that they also didn't go extinct and will continue to thrive in the future. On the other end of the spectrum you actually can have runaway adaptation, especially when there's a kind of "arms race" between predator and prey. The cheetah is so hyper-specialised for catching its prey by speed alone that it's a kind of evolutionary dead-end; it can't zig-zag like the gazelle can. Anyway, the stair-step attitude originates from outside of biology, from Platonic thinking that there are "higher" ideal forms. And the sudden changes turn out not to be "few and far between", they just don't seem to stick. Most adaptations average out, because they're highly contextual to their short time periods. As mentioned, since we based our first ideas about evolution on fossils, we only noticed the slow evolution. Sex actually seems to play a large part in the filtering process[1]: > For a species whose numbers show no signs of collapsing, humans have a shockingly high mutation rate. Each of us is born with about 70 new genetic errors that our parents did not have. That’s much more than a slime mold, say, or a bacterium. Mutations are likely to decrease an organism’s fitness, and an avalanche like this every generation could be deadly to our species. The fact that we haven’t gone extinct suggests that over the long term, we have some way of taking out our genetic garbage. And a new paper, recently published in Science, provides evidence that the answer may be linked to another fascinating procedure: sex. (...) As the number of nasty genetic errors in a population rises, natural selection will sweep large rafts of them out of the genome together. And in sexual organisms, because of the ways that mutations from each parent can recombine randomly onto the same chromosomes, the synergistic elimination of bad mutations can happen even faster. Anyway, hope this addresses some of your understandable scepticism! [0] https://www.quantamagazine.org/evolution-runs-faster-on-short-timescales-20170314/ https://www.quantamagazine.org/evolution-runs-faster-on-shor... [1] https://www.quantamagazine.org/missing-mutations-suggest-a-reason-for-sex-20170713/ https://www.quantamagazine.org/missing-mutations-suggest-a-r...

rxhernandez 9y ago

I mean, I'm assuming these people are professional biologists of some sort, that have probably spent decades in their field. Not only that but they would know more about how evolution works than the average college educated layperson. I'm a little frustrated to point that out. However my frustration isn't enough to motivate my next question. What did you hope to accomplish, in light of these problems, by criticizing these scientists' work with what is ostensibly, cursory popular science knowledge? I guess I just want to understand why there is a mistrust for professional scientists even on a site as technologically inclined as HN.

hellofunk 9y ago
> I guess I just want to understand why there is a mistrust for professional scientists even on a site as technologically inclined as HN. I think you are new to HN. There is a long history of healthy skepticism by the readers here of studies posted in a wide range of fields. Healthy skepticism, or at least, pointing out remarkable and hard-to-believe aspects of a reported study (as I did here), is quite commonplace all over HN. In fact, if you read any of the nearly hundred other comments in this thread, you will see equal amounts of skepticism, some more verbose, some more terse, than what I expressed. Fortunately, you did not go and criticize those commenters also. In the case of evolution, I was taught years ago in school that evolution is not a gradual and linear process, and that often very long stretches occur with zero evolutionary action, then a single evolutionary event causes a gigantic leap of changes in a species, a single spike, which then plateaus again for a long time another spike. I am not an evolutionary scientist of course, but I was leaning on that, and layman's perception of evolution, in my comment. I'm frustrated to have to point this out. What did you hope to accomplish by criticising my reaction to the article? Are we not all here to comment on our opinions and reactions to the items posted? Just because you do not agree with my particular reaction to the article does not mean you should make such wide assumptions about my own motivations (or those of any other reader you choose to attack in the future).

haihaibye 9y ago

Imagine a conception occurs with a random mutation that causes a miscarriage. That's evolution in a few months. Imagine one that causes someone to be infertile. The balance of genetics changes (evolution) in a generation. Africa went from 1/2 the population of Europe in 1950 to 1.6x the size today. The gene frequencies on those two continents are different - thus there has clearly been differential fitness (in the hundreds of millions in a lifetime)

hellofunk 9y ago
> That's evolution in a few months. A single isolated event with no impact on the species is not the definition that most would use for evolution. And even if it had an effect on that individual family, evolution is about nature selecting that particular mutation, which may not happen at all. So I don't support the premise of your argument.
- haihaibye 9y ago
  Evolution is the change in gene frequencies over time. Accepting my premise is just knowing the textbook definition. I think what you are trying to describe is "novel fitness increasing mutations" - these won't be detectable for ages as it takes time to spread through a population. Single isolated events matter - All mutations start off in an individual, they then increase or decrease in frequency.