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>But evolution is a random process based on the short-term advantages that emerge in each generation. This idea is easily discredited, even "disadvantageous-bu

by ouid 9y ago

>But evolution is a random process based on the short-term advantages that emerge in each generation. This idea is easily discredited, even "disadvantageous-but-viable" mutations are prized possessions among my offspring. Environments change, and whether or not my lineage goes unbroken is a result of its ability to survive those changes. Those environmental changes are unpredictable. phenotypes that benefit me now do not necessarily benefit me in the future. If it is my goal to extend my lineage as long as possible, then my optimal strategy must give extra value to diversity. Since every organism possesses a lineage that goes back to the origin of life, it's fair to say that cooperation for the goal of increasing diversity is a pretty heavily selected for trait.

onychomys 9y ago
You're basically arguing for a species-level (or at least a deme-level) view of selection. That's something that we've tried to find for many decades, and there just isn't a lot of evidence for it. Selection happens at the level of the individual animal, not any higher grouping.
- jawarner 9y ago
  Why doesn't Hamilton's rule or evolutionary game theory in general justify a social-network aware view of evolution? What evidence or theoretical argument would constitute a species level view of selection?
- statevol 9y ago
  I've taught evolutionary biology to non-biology majors and the way I would explain natural selection is as follows. First, to clarify the last sentence above, selection does not happen at the level of an individual. Selection is a statistical process that requires a population of individuals. For evolution by selection to occur, there has to be 1) variation in traits (i.e. "Phenotypes"), 2) the variation in these traits has to be in part heritible (i.e. Have a genetic basis), and 3) there have to be average differences in success of leaving offspring that themseves go on to reproduce, etc, etc, based on the trait differences amongst individuas.
  - int_19h 9y ago
    But diversity is not a phenotype in any meaningful way, is it?
    - akvadrako 9y ago
      Well you can either have a reproduction mechanism that encourages diversity or doesn't. That seems like a trait to me.
- ouid 9y ago
  I'm not sure what you think selection is. Organisms which do not have diverse offspring are very unlikely to maintain a lineage through big changes to the environment. Big changes to the environment are frequent. Therefore diversity of offspring, as a trait, is selected for.
  - jballanc 9y ago
    Unless big changes to the environment happen at least once every generation, then there is no way that diversity of offspring will be selected for. Say you have a population of 100,000 organisms and 1 randomly mutates to produce more diverse offspring. That gives the gene a 0.001% occurrence in the population. Hardy-Weinberg principle says that gene will remain at about that percent of the population unless it is selected for. So if a generation passes without selection for that trait, there is a very high probability that gene's occurrence drops back to 0%. In other words, without a constant source of selection, there is no way for a trait to become fixed in a population.
hackinthebochs 9y ago
>it's fair to say that cooperation for the goal of increasing diversity is a pretty heavily selected for trait. It seems like you're making the mistake of thinking that traits we see were necessarily being actively selected for. It's like saying that because we see an increase in complexity in organisms over time, that evolution is selecting for complexity (its not). It's true that more diverse populations can withstand changes to the environment better. But to then say that the trait of diversity is selected for is a huge stretch. If diversity has no current value then it won't be selected for, and will be selected against in competitive environments. Evolution doesn't have a way to see into the future in that way. Diversity might be selected for in cooperative populations, but only when diverse behavior provides an immediate benefit to the population.
- jawarner 9y ago
  > Evolution doesn't have a way to see into the future in that way. Model A: Let's say there is an environmental change every 100 years, and if a population is not diverse enough, then it dies. After 1000 years, we would expect the only populations to be around would be those that are diverse. Yes, it is true that if there there is a short-term advantage to nondiversity in a population, then it will evolve to be nondiverse, and it will die - in this sense you're right that evolution does not see into the future. However, given the existence of diverse populations assuming the Model A, we can conclude that these populations have found a local minimum of fitness in which diversity is advantageous. Further, there might be "genetic guards" to nondiversity, such that fixation of a gene promoting nondiversity is rare (because this would resilt in extinction!), either through social sexual selection or by such a mutation being a rare event.
  - hackinthebochs 9y ago
    >However, given the existence of diverse populations assuming the Model A, we can conclude that these populations have found a local minimum of fitness in which diversity is advantageous. But any mechanism in which "diversity" is advantageous will be advantageous for more specific reasons. Diversity is just too unspecific. Perhaps you're speaking in terms of group selection, so in a sense evolution evolves diversity in populations. But I don't think this works either. Aside from group selection itself being highly questionable, every environmental event in your Model A would reduce the diversity of the remaining populations. Remaining populations were more diverse in the past (owing to their ability to survive abrupt environmental shifts), so any trend in diversity is in fact downward on large timescales. On short timescales, diversity only grows when there are no selective pressures at work on a given gene. There just is no pro-diversity selection going on.
irickt 9y ago
Cause in the opposite direction may be more fundamental, though in evolution all cause is circular. Because the world is variable a necessary adaptation in every lineage is a corresponding variability in each of its systems, subject to homeostasis. Combinations of this variability may then happen to offer survival of new challenges. So yes specific diversity is selected but it's because general diversity has been there from the beginning. The article doesn't address this second-order effect of innovation. Instead it seems to take a basic result of evolutionary game theory and cast it in a model from physics.
partycoder 9y ago
What makes a trait advantageous is very relative. Having a slow metabolism is usually bad, but if there's food shortage it becomes an advantageous trait. Dwarfism is similar. That's why larger/stronger/faster cats like the saber-toothed cats died and now we have smaller cats, for instance.
daemonk 9y ago
You should read up on cryptic mutations. I don't think it is that popular in the evolutionary biology field though, mainly because it can be a very vague mechanism.

by ouid 9y ago

onychomys 9y ago

You're basically arguing for a species-level (or at least a deme-level) view of selection. That's something that we've tried to find for many decades, and there just isn't a lot of evidence for it. Selection happens at the level of the individual animal, not any higher grouping.

jawarner 9y ago
Why doesn't Hamilton's rule or evolutionary game theory in general justify a social-network aware view of evolution? What evidence or theoretical argument would constitute a species level view of selection?
statevol 9y ago
I've taught evolutionary biology to non-biology majors and the way I would explain natural selection is as follows. First, to clarify the last sentence above, selection does not happen at the level of an individual. Selection is a statistical process that requires a population of individuals. For evolution by selection to occur, there has to be 1) variation in traits (i.e. "Phenotypes"), 2) the variation in these traits has to be in part heritible (i.e. Have a genetic basis), and 3) there have to be average differences in success of leaving offspring that themseves go on to reproduce, etc, etc, based on the trait differences amongst individuas.
- int_19h 9y ago
  But diversity is not a phenotype in any meaningful way, is it?
  - akvadrako 9y ago
    Well you can either have a reproduction mechanism that encourages diversity or doesn't. That seems like a trait to me.
ouid 9y ago
I'm not sure what you think selection is. Organisms which do not have diverse offspring are very unlikely to maintain a lineage through big changes to the environment. Big changes to the environment are frequent. Therefore diversity of offspring, as a trait, is selected for.
- jballanc 9y ago
  Unless big changes to the environment happen at least once every generation, then there is no way that diversity of offspring will be selected for. Say you have a population of 100,000 organisms and 1 randomly mutates to produce more diverse offspring. That gives the gene a 0.001% occurrence in the population. Hardy-Weinberg principle says that gene will remain at about that percent of the population unless it is selected for. So if a generation passes without selection for that trait, there is a very high probability that gene's occurrence drops back to 0%. In other words, without a constant source of selection, there is no way for a trait to become fixed in a population.

hackinthebochs 9y ago

>it's fair to say that cooperation for the goal of increasing diversity is a pretty heavily selected for trait. It seems like you're making the mistake of thinking that traits we see were necessarily being actively selected for. It's like saying that because we see an increase in complexity in organisms over time, that evolution is selecting for complexity (its not). It's true that more diverse populations can withstand changes to the environment better. But to then say that the trait of diversity is selected for is a huge stretch. If diversity has no current value then it won't be selected for, and will be selected against in competitive environments. Evolution doesn't have a way to see into the future in that way. Diversity might be selected for in cooperative populations, but only when diverse behavior provides an immediate benefit to the population.

jawarner 9y ago
> Evolution doesn't have a way to see into the future in that way. Model A: Let's say there is an environmental change every 100 years, and if a population is not diverse enough, then it dies. After 1000 years, we would expect the only populations to be around would be those that are diverse. Yes, it is true that if there there is a short-term advantage to nondiversity in a population, then it will evolve to be nondiverse, and it will die - in this sense you're right that evolution does not see into the future. However, given the existence of diverse populations assuming the Model A, we can conclude that these populations have found a local minimum of fitness in which diversity is advantageous. Further, there might be "genetic guards" to nondiversity, such that fixation of a gene promoting nondiversity is rare (because this would resilt in extinction!), either through social sexual selection or by such a mutation being a rare event.
- hackinthebochs 9y ago
  >However, given the existence of diverse populations assuming the Model A, we can conclude that these populations have found a local minimum of fitness in which diversity is advantageous. But any mechanism in which "diversity" is advantageous will be advantageous for more specific reasons. Diversity is just too unspecific. Perhaps you're speaking in terms of group selection, so in a sense evolution evolves diversity in populations. But I don't think this works either. Aside from group selection itself being highly questionable, every environmental event in your Model A would reduce the diversity of the remaining populations. Remaining populations were more diverse in the past (owing to their ability to survive abrupt environmental shifts), so any trend in diversity is in fact downward on large timescales. On short timescales, diversity only grows when there are no selective pressures at work on a given gene. There just is no pro-diversity selection going on.

irickt 9y ago

Cause in the opposite direction may be more fundamental, though in evolution all cause is circular. Because the world is variable a necessary adaptation in every lineage is a corresponding variability in each of its systems, subject to homeostasis. Combinations of this variability may then happen to offer survival of new challenges. So yes specific diversity is selected but it's because general diversity has been there from the beginning. The article doesn't address this second-order effect of innovation. Instead it seems to take a basic result of evolutionary game theory and cast it in a model from physics.

partycoder 9y ago

What makes a trait advantageous is very relative. Having a slow metabolism is usually bad, but if there's food shortage it becomes an advantageous trait. Dwarfism is similar. That's why larger/stronger/faster cats like the saber-toothed cats died and now we have smaller cats, for instance.

daemonk 9y ago

You should read up on cryptic mutations. I don't think it is that popular in the evolutionary biology field though, mainly because it can be a very vague mechanism.