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From a purely mathematical perspective, how would evolution ever select for a trait that causes someone to destroy themselves for the benefit of others? It see

From a purely mathematical perspective, how would evolution ever select for a trait that causes someone to destroy themselves for the benefit of others? It seems like any characteristic that prevents the individual from reproducing is by definition not selected for. But I could be misunderstanding something. Maybe it could work in the case of people who are already parents. Favoring the group could increase the likeliness of their children surviving perhaps?

TeMPOraL 11y ago
It's easy to make evolutionary just-so stories and they're usually worthless anyway, but here's my attempt at one: as an animal, if you reach a certain age and are not already a parent, it means you're deficient. It's better for the gene pool if you die without reproducing. If you're a parent and you did all that was needed for the offspring to survive the early development period, you're no longer needed and probably better off dying instead of consuming resources your children need.
- haberman 11y ago
  Yes I generally hate evolutionary just-so stories. > if you reach a certain age and are not already a parent, it means you're deficient. It's better for the gene pool if you die without reproducing. This explanation makes no sense to me. Evolution doesn't select for the overall gene pool AIUI, it selects for fit individuals. I can't see how, even in theory, this explanation would be plausible. > If you're a parent and you did all that was needed for the offspring to survive the early development period, you're no longer needed and probably better off dying instead of consuming resources your children need. This explanation sounds at least mathematically plausible to me.
- fucking_tragedy 11y ago
  How does this explain the higher rate of suicidal ideation/actions in depressed adolescents who are at their biological prime for reproduction?
  - TeMPOraL 11y ago
    I don't know. Except maybe that biologically they're supposed to have children instead of sitting in school and waiting for marriage, home and a job.
    - yarou 11y ago
      No idea what this means if you're a male. Males are fertile forever basically, so there isn't some "optimal" age to have offspring. By your logic, males should be continuously fathering offspring throughout their lives, as soon as they reach puberty.
tbirdz 11y ago
The individual would still have other relatives who would pass on the genes, like sisters, brothers, other family members. If the individual's sacrifice helps the group survive, their genes would be passed on in those relatives. Also note that the gene would only be activated under a certain set of circumstances, so individuals could have the "self-sacrifice" gene and pass it to their children, even if they never encountered the set of circumstances that would induce suicidal ideation themselves. I believe there is similar thinking for genetic passing of traits like homosexuality.
- haberman 11y ago
  That explanation doesn't make sense to me. Your brothers/sisters etc. have similar genes, but they don't have your genes. The theory of evolution is that the most fit genes propagate. So if your brothers/sisters propagate but you don't, then your brothers/sisters genes (along with whatever mutations they might have) are being selected over yours, just as if you had some mutation that made you overall less fit.
  - tbirdz 11y ago
    The most fit genes propagate, not the most fit individuals. Your siblings have many of the same genes that you have. Say there is a gene A that will result in some individuals not reproducing, but will result in more members of their group reproducing. Now say there is 1 group where the members of the group have gene A, and another group where the members don't have gene A. Over time the group with gene A will reproduce more than the group without A, resulting in more copies of A in the general population. Even if some individuals in the group do not reproduce, their relatives in the group do reproduce. So say 1 person self-sacrifices and does not reproduce, and as a result of their sacrifice 10 others in the group survive and reproduce that would not have been able to if the first individual had not self sacrificed. The family all has gene A, so this results in a net gain of 9 individuals with gene A. So the amount of people with gene A increases, even though some individuals with gene A potentially do not survive and reproduce. If you want to learn more about this kind of thing, look into "Selfish Gene Theory".
berntb 11y ago
Read "The Selfish Gene", or some other book that go over this research. That book is a good choice, it is probably one of the best popular science books you will read in your life. (The research is well corroborated, except by some Marxist biologists. :-) ) You can start by checking this: https://en.wikipedia.org/wiki/W._D._Hamilton https://en.wikipedia.org/wiki/W._D._Hamilton
imgabe 11y ago
Not every trait that exists has to be selected for. It just has to not be selected against enough for it to be completely wiped out. Some people procreate before they commit suicide, even those that don't would have relatives who might have been spared by different circumstances, or a slightly different mix of genes.
chillwaves 11y ago
https://en.wikipedia.org/wiki/Group_selection https://en.wikipedia.org/wiki/Group_selection
joncrocks 11y ago
Sometimes traits are related, or negative traits are only manifest in a recessive manner. In such a way positive traits can be selected for, which have a consequence of a negative trait being present in a population. The example frequently citied in this area is sickle cell anaemia, which can be inadvertently selected for in areas where Malaria is common. Having one 'bad' gene protects the person from Malaria, having two means that one has sickle cell anaemia. This means that people with a single gene are more likely to survive, and hence pass on their gene, but this sometimes manifests as someone with sickle cell anaemia. See https://en.wikipedia.org/wiki/Sickle-cell_disease#Epidemiology https://en.wikipedia.org/wiki/Sickle-cell_disease#Epidemiolo...

TeMPOraL 11y ago

It's easy to make evolutionary just-so stories and they're usually worthless anyway, but here's my attempt at one: as an animal, if you reach a certain age and are not already a parent, it means you're deficient. It's better for the gene pool if you die without reproducing. If you're a parent and you did all that was needed for the offspring to survive the early development period, you're no longer needed and probably better off dying instead of consuming resources your children need.

haberman 11y ago
Yes I generally hate evolutionary just-so stories. > if you reach a certain age and are not already a parent, it means you're deficient. It's better for the gene pool if you die without reproducing. This explanation makes no sense to me. Evolution doesn't select for the overall gene pool AIUI, it selects for fit individuals. I can't see how, even in theory, this explanation would be plausible. > If you're a parent and you did all that was needed for the offspring to survive the early development period, you're no longer needed and probably better off dying instead of consuming resources your children need. This explanation sounds at least mathematically plausible to me.
fucking_tragedy 11y ago
How does this explain the higher rate of suicidal ideation/actions in depressed adolescents who are at their biological prime for reproduction?
- TeMPOraL 11y ago
  I don't know. Except maybe that biologically they're supposed to have children instead of sitting in school and waiting for marriage, home and a job.
  - yarou 11y ago
    No idea what this means if you're a male. Males are fertile forever basically, so there isn't some "optimal" age to have offspring. By your logic, males should be continuously fathering offspring throughout their lives, as soon as they reach puberty.

tbirdz 11y ago

The individual would still have other relatives who would pass on the genes, like sisters, brothers, other family members. If the individual's sacrifice helps the group survive, their genes would be passed on in those relatives. Also note that the gene would only be activated under a certain set of circumstances, so individuals could have the "self-sacrifice" gene and pass it to their children, even if they never encountered the set of circumstances that would induce suicidal ideation themselves. I believe there is similar thinking for genetic passing of traits like homosexuality.

haberman 11y ago
That explanation doesn't make sense to me. Your brothers/sisters etc. have similar genes, but they don't have your genes. The theory of evolution is that the most fit genes propagate. So if your brothers/sisters propagate but you don't, then your brothers/sisters genes (along with whatever mutations they might have) are being selected over yours, just as if you had some mutation that made you overall less fit.
- tbirdz 11y ago
  The most fit genes propagate, not the most fit individuals. Your siblings have many of the same genes that you have. Say there is a gene A that will result in some individuals not reproducing, but will result in more members of their group reproducing. Now say there is 1 group where the members of the group have gene A, and another group where the members don't have gene A. Over time the group with gene A will reproduce more than the group without A, resulting in more copies of A in the general population. Even if some individuals in the group do not reproduce, their relatives in the group do reproduce. So say 1 person self-sacrifices and does not reproduce, and as a result of their sacrifice 10 others in the group survive and reproduce that would not have been able to if the first individual had not self sacrificed. The family all has gene A, so this results in a net gain of 9 individuals with gene A. So the amount of people with gene A increases, even though some individuals with gene A potentially do not survive and reproduce. If you want to learn more about this kind of thing, look into "Selfish Gene Theory".

berntb 11y ago

Read "The Selfish Gene", or some other book that go over this research. That book is a good choice, it is probably one of the best popular science books you will read in your life. (The research is well corroborated, except by some Marxist biologists. :-) ) You can start by checking this: https://en.wikipedia.org/wiki/W._D._Hamilton https://en.wikipedia.org/wiki/W._D._Hamilton

imgabe 11y ago

Not every trait that exists has to be selected for. It just has to not be selected against enough for it to be completely wiped out. Some people procreate before they commit suicide, even those that don't would have relatives who might have been spared by different circumstances, or a slightly different mix of genes.

chillwaves 11y ago

https://en.wikipedia.org/wiki/Group_selection https://en.wikipedia.org/wiki/Group_selection

joncrocks 11y ago

Sometimes traits are related, or negative traits are only manifest in a recessive manner. In such a way positive traits can be selected for, which have a consequence of a negative trait being present in a population. The example frequently citied in this area is sickle cell anaemia, which can be inadvertently selected for in areas where Malaria is common. Having one 'bad' gene protects the person from Malaria, having two means that one has sickle cell anaemia. This means that people with a single gene are more likely to survive, and hence pass on their gene, but this sometimes manifests as someone with sickle cell anaemia. See https://en.wikipedia.org/wiki/Sickle-cell_disease#Epidemiology https://en.wikipedia.org/wiki/Sickle-cell_disease#Epidemiolo...