4 ms·

> But as the quality of the germ cells declines, there is no evolutionary reason to keep extending life span further; from evolution’s perspective, life exists

by yarg 3y ago

> But as the quality of the germ cells declines, there is no evolutionary reason to keep extending life span further; from evolution’s perspective, life exists to reproduce itself. When the individual's survival is the only selection factor, this is true - but it ceases to be the case in social species where reproductively non-viable individuals can still positively influence the reproductive chances of the young. This may be an indirect feedback loop - but a little bit of latency doesn't make a huge difference when you're dealing with hundreds of thousands of generations of natural selection.

wcoenen 3y ago
The survival of the individual is indeed not what natural selection is selecting for. Otherwise phenomena like eusocial insects with sterile workers would not make sense. What is actually selected for, is genes that somehow promote more copies of themselves. This is the main takeaway from the book "the selfish gene". However, the example of ants and bees shows that this doesn't exactly promote long lifespan in the sterile workers... Instead, they are mass-produced expendable drones.
- wegfawefgawefg 3y ago
  I think the common notion is that the survival of the individual is exactly what natural selection is selecting for. However, it seems to me its more selecting for its own particular configuration of genes, that essentially select for a signature of themself. Within a species the configuration between individuals is generally different enough to not ellicit altruistic behaviour. In most animals, the 50% kinship gene relatedness threshold is definitely not enough to instigate self sacrificial behaviour. The children of a usocial species have to be like 11/16ths clones of eachother. And the runt suicide mechanism that triggers in rabbits requires a brood of true clones. The reason I think it seems the genes select for individuals is because most circumstances will recquire that the current reproductive unit at the individual level needs to stay alive long enough for a net positive replication contribution to have been made.
  - fsckboy 3y ago
    > I think the common notion is that the survival of the individual is exactly what natural selection is selecting for. when we reproduce, do we make copies of ourselves? no we don't. It's not survival of individuals. Read the Selfish Gene and it will change your thinking. You as an individual are a piece of clothing for your genes. Your genes reproduce, you don't.
    - AnthonyMouse 3y ago
      > Your genes reproduce, you don't. It's more complicated than that. Your genes reproduce, but then that child is in your care, and you teach them your values. Then your values reproduce. And then you're into nature vs. nurture. Your values can't reproduce if you have stupid genes that cause your offspring to die of cystic fibrosis, but your genes can't reproduce if you have stupid values that cause your offspring to be self-destructive and sterile. "You" are the combination of your genes and your values, and whether there gets to be any more of that depends on whether you, as a whole, are any good at it.
      - startupsfail 3y ago
        Yep. The immune system is watching for that and killing you off, if you’re being a social reject. That works for any social animal. Plus for humans there’s also a suicide trick.
        d1sxeyes 3y ago
        Not sure if you're being facetious or not, but it's not the immune system killing you off. That said, you are less likely to reproduce successfully if you are 'a social reject'. You will meet fewer potential mates, fewer of those will be willing to reproduce with you, etc. Whatever it was that made you a social reject, if it's something you can pass on either through nature or nuture, is less likely to be passed on.
        wegfawefgawefg 3y ago
- jacquesm 3y ago
  > Otherwise phenomena like eusocial insects with sterile workers would not make sense. These are often genetically identical with the rest of the hive, just on a different diet and with different treatment after the eggs are laid.
- yarg 3y ago
  The survival of the individual is exactly what is being selected for. The influence of an individual gene is not distinguishable from those that are packaged with it. So what is selected for over any single cycle is sets of sets of genes conveying advantage. Taking half of your genes from each parent could only select whole useful chromosomes from each parent (but is far better than nothing); In order for genes to be selected in their own rights, you need more. Chromosomal crossover copies genes across chromosome pairs - over the course of repeated iterations this allows useful mutations to be more easily distinguished. https://en.wikipedia.org/wiki/Chromosomal_crossover https://en.wikipedia.org/wiki/Chromosomal_crossover
  - hgomersall 3y ago
    There are plenty of ways in which the genes of an individual may survive better when the individual has reduced survival. The individual in this case being the large multicellular organism. Hence we see all sorts of weird strategies in the wild like sexual cannibalism: https://en.m.wikipedia.org/wiki/Sexual_cannibalism https://en.m.wikipedia.org/wiki/Sexual_cannibalism
  - wcoenen 3y ago
    > The survival of the individual is exactly what is being selected for. The influence of an individual gene is not distinguishable from those that are packaged with it. Here is a counterexample where a gene or set of genes jumped ship and untethered itself from the individual they were originally embedded in: https://en.wikipedia.org/wiki/Devil_facial_tumour_disease https://en.wikipedia.org/wiki/Devil_facial_tumour_disease

by yarg 3y ago

wcoenen 3y ago

The survival of the individual is indeed not what natural selection is selecting for. Otherwise phenomena like eusocial insects with sterile workers would not make sense. What is actually selected for, is genes that somehow promote more copies of themselves. This is the main takeaway from the book "the selfish gene". However, the example of ants and bees shows that this doesn't exactly promote long lifespan in the sterile workers... Instead, they are mass-produced expendable drones.

wegfawefgawefg 3y ago
I think the common notion is that the survival of the individual is exactly what natural selection is selecting for. However, it seems to me its more selecting for its own particular configuration of genes, that essentially select for a signature of themself. Within a species the configuration between individuals is generally different enough to not ellicit altruistic behaviour. In most animals, the 50% kinship gene relatedness threshold is definitely not enough to instigate self sacrificial behaviour. The children of a usocial species have to be like 11/16ths clones of eachother. And the runt suicide mechanism that triggers in rabbits requires a brood of true clones. The reason I think it seems the genes select for individuals is because most circumstances will recquire that the current reproductive unit at the individual level needs to stay alive long enough for a net positive replication contribution to have been made.
- fsckboy 3y ago
  > I think the common notion is that the survival of the individual is exactly what natural selection is selecting for. when we reproduce, do we make copies of ourselves? no we don't. It's not survival of individuals. Read the Selfish Gene and it will change your thinking. You as an individual are a piece of clothing for your genes. Your genes reproduce, you don't.
  - AnthonyMouse 3y ago
    > Your genes reproduce, you don't. It's more complicated than that. Your genes reproduce, but then that child is in your care, and you teach them your values. Then your values reproduce. And then you're into nature vs. nurture. Your values can't reproduce if you have stupid genes that cause your offspring to die of cystic fibrosis, but your genes can't reproduce if you have stupid values that cause your offspring to be self-destructive and sterile. "You" are the combination of your genes and your values, and whether there gets to be any more of that depends on whether you, as a whole, are any good at it.
    - startupsfail 3y ago
      Yep. The immune system is watching for that and killing you off, if you’re being a social reject. That works for any social animal. Plus for humans there’s also a suicide trick.
      - d1sxeyes 3y ago
        Not sure if you're being facetious or not, but it's not the immune system killing you off. That said, you are less likely to reproduce successfully if you are 'a social reject'. You will meet fewer potential mates, fewer of those will be willing to reproduce with you, etc. Whatever it was that made you a social reject, if it's something you can pass on either through nature or nuture, is less likely to be passed on.
        wegfawefgawefg 3y ago
jacquesm 3y ago
> Otherwise phenomena like eusocial insects with sterile workers would not make sense. These are often genetically identical with the rest of the hive, just on a different diet and with different treatment after the eggs are laid.
yarg 3y ago
The survival of the individual is exactly what is being selected for. The influence of an individual gene is not distinguishable from those that are packaged with it. So what is selected for over any single cycle is sets of sets of genes conveying advantage. Taking half of your genes from each parent could only select whole useful chromosomes from each parent (but is far better than nothing); In order for genes to be selected in their own rights, you need more. Chromosomal crossover copies genes across chromosome pairs - over the course of repeated iterations this allows useful mutations to be more easily distinguished. https://en.wikipedia.org/wiki/Chromosomal_crossover https://en.wikipedia.org/wiki/Chromosomal_crossover
- hgomersall 3y ago
  There are plenty of ways in which the genes of an individual may survive better when the individual has reduced survival. The individual in this case being the large multicellular organism. Hence we see all sorts of weird strategies in the wild like sexual cannibalism: https://en.m.wikipedia.org/wiki/Sexual_cannibalism https://en.m.wikipedia.org/wiki/Sexual_cannibalism
- wcoenen 3y ago
  > The survival of the individual is exactly what is being selected for. The influence of an individual gene is not distinguishable from those that are packaged with it. Here is a counterexample where a gene or set of genes jumped ship and untethered itself from the individual they were originally embedded in: https://en.wikipedia.org/wiki/Devil_facial_tumour_disease https://en.wikipedia.org/wiki/Devil_facial_tumour_disease