Salmon swimming upstream to their birthing grounds to breed may be that rare form of group selection.
Pure Aryan Salmon
Salmon engage in anodromous reproduction; they risk their lives to swim up rivers to return to their original place of birth and reproduce there.
Most species of salmon die there, only reproducing at the birthing grounds. Many don’t make it at all. The ones that survive the run upstream will die shortly after, a biologically triggered death sentence. If the cost is immense—the benefits must be even greater.
The more upstream the saver. The solid magikarp babies are saver the more upstream as the lakes and pools and fountainheads high up support less predators. Downstream there are more nutrients so as the magikarps grow larger they move downstream. This makes perfect sense and plausibly explain the behaviour. but it recently struck me that there is also a group selection story here.
Not all species are created equal. Some species are simply more biologically fit than others. For instance, the native Australian fauna generically canot compete with Old World fauna. Ditto for many island fauna.
How could this be? Aren’t all animals equally selected to reproduce? Not all environments are the same. Maintaining biological vigor in the face of mutational load is difficult. The amount of purifying selection is a major factor in the level of mutational load and biological vigor of a species. [1]
Group selection is a hypothesized form of selection that acts at the level of the group rather than that of the individual. Group selection has gotten a bad rap. In the vast majority of the cases hypothesized group selection is better explained by selection at the level of the gene. The math of group selection shakes out in such a way that it is rarely a strong enough effect.
An exception that is sometimes mentioned is the emergence and exctinction of asexual species. Although being asexual makes one more fecund in the short run, in the long run it prevents one from doing sexual recombination. Asexual species universally seem to have come into being very recently. They likely go extinct due to lack of genetic diversity and attendant mutational load catastrophe and/or losing arms races with parasites.
The equilibrium of swimming back to the ancestral pool to reproduct would seem like an insane practice on the face of it. Why go through all this effort?
One explanationc could be that anodromous reproduction is a stable game-theoretic equilibrium in which the selective pressure on the salmon species is higher encouraging higher biological fitness.
Salmon that deviate from the practice either don’t get to mate or if they mate they are reproductively isolated from the other salmon and become a different species.
This group selection hypothesis makes predictions about the biological vigor and mutational load of salmon and could be, is likely, false.
Another important factor for the strength of selection is the effective population size which I will pass over in silence for the moment. But if you’re interested in this topic I suggest you acquaint yourself with this topic as it is probably the most important and least understood concept in evolutionary biology.
I am confused about what I’m reading. The magikarp gave me a doubletake and like “wait, are magikarp also just a totally real fish?” but after some googling it seems like “nope, that’s really just a pokemon”, and now I can’t tell if the rest of the post is like a parody or what.
This seems fairly normal for an Alexander post to me (actually, more understandable than the median Alexander shortform). I think the magikarp is meant to be 1) an obfuscation of salamon, and 2) a reference to solid gold magikarp.
After rereading it like 4 times I am now less convinced it’s GPT output. I still feel confused about a lot of sentences, but I think half of it was just the lack of commas in sentences like “One explanationc could be that anodromous reproduction is a stable game-theoretic equilibrium in which the selective pressure on the salmon species is higher encouraging higher biological fitness”.
The solid magikarp babies are saver the more upstream as the lakes and pools and fountainheads high up support less predators. Downstream there are more nutrients so as the magikarps grow larger they move downstream.
Asexual species universally seem to have come into being very recently. They likely go extinct due to lack of genetic diversity and attendant mutational load catastrophe and/or losing arms races with parasites.
Bdelloidea are an interesting counterexample: they evolved obligate parthenogenesis ~25 mya.
My understanding from reading Mitochondria: Power, Sex, Suicide is that they are not truly asexual but turn out to do some sexual recombination. I don’t remember the details and I’m not an expert though so wouldn’t put my hand in the fire for it.
tl;dr
Salmon swimming upstream to their birthing grounds to breed may be that rare form of group selection.
Pure Aryan Salmon
Salmon engage in anodromous reproduction; they risk their lives to swim up rivers to return to their original place of birth and reproduce there.
Most species of salmon die there, only reproducing at the birthing grounds. Many don’t make it at all. The ones that survive the run upstream will die shortly after, a biologically triggered death sentence. If the cost is immense—the benefits must be even greater.
The more upstream the saver. The solid magikarp babies are saver the more upstream as the lakes and pools and fountainheads high up support less predators. Downstream there are more nutrients so as the magikarps grow larger they move downstream. This makes perfect sense and plausibly explain the behaviour. but it recently struck me that there is also a group selection story here.
Not all species are created equal. Some species are simply more biologically fit than others. For instance, the native Australian fauna generically canot compete with Old World fauna. Ditto for many island fauna.
How could this be? Aren’t all animals equally selected to reproduce? Not all environments are the same. Maintaining biological vigor in the face of mutational load is difficult. The amount of purifying selection is a major factor in the level of mutational load and biological vigor of a species. [1]
Group selection is a hypothesized form of selection that acts at the level of the group rather than that of the individual. Group selection has gotten a bad rap. In the vast majority of the cases hypothesized group selection is better explained by selection at the level of the gene. The math of group selection shakes out in such a way that it is rarely a strong enough effect.
An exception that is sometimes mentioned is the emergence and exctinction of asexual species. Although being asexual makes one more fecund in the short run, in the long run it prevents one from doing sexual recombination. Asexual species universally seem to have come into being very recently. They likely go extinct due to lack of genetic diversity and attendant mutational load catastrophe and/or losing arms races with parasites.
The equilibrium of swimming back to the ancestral pool to reproduct would seem like an insane practice on the face of it. Why go through all this effort?
One explanationc could be that anodromous reproduction is a stable game-theoretic equilibrium in which the selective pressure on the salmon species is higher encouraging higher biological fitness.
Salmon that deviate from the practice either don’t get to mate or if they mate they are reproductively isolated from the other salmon and become a different species.
This group selection hypothesis makes predictions about the biological vigor and mutational load of salmon and could be, is likely, false.
Another important factor for the strength of selection is the effective population size which I will pass over in silence for the moment. But if you’re interested in this topic I suggest you acquaint yourself with this topic as it is probably the most important and least understood concept in evolutionary biology.
I am confused about what I’m reading. The magikarp gave me a doubletake and like “wait, are magikarp also just a totally real fish?” but after some googling it seems like “nope, that’s really just a pokemon”, and now I can’t tell if the rest of the post is like a parody or what.
This post feels like raw GPT-3 output. It’s not even GPT-3.5 or GPT-4 level, which makes this additionally confusing.
Maybe a result of playing around with base models?
This seems fairly normal for an Alexander post to me (actually, more understandable than the median Alexander shortform). I think the magikarp is meant to be 1) an obfuscation of salamon, and 2) a reference to solid gold magikarp.
@Raemon
After rereading it like 4 times I am now less convinced it’s GPT output. I still feel confused about a lot of sentences, but I think half of it was just the lack of commas in sentences like “One explanationc could be that anodromous reproduction is a stable game-theoretic equilibrium in which the selective pressure on the salmon species is higher encouraging higher biological fitness”.
Please tell us more about the magikarps.
Bdelloidea are an interesting counterexample: they evolved obligate parthenogenesis ~25 mya.
My understanding from reading Mitochondria: Power, Sex, Suicide is that they are not truly asexual but turn out to do some sexual recombination. I don’t remember the details and I’m not an expert though so wouldn’t put my hand in the fire for it.