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I often wonder what the effects of reduced infant mortality will be on the population. For all of human history before about 100 years ago, we were aggressively

I often wonder what the effects of reduced infant mortality will be on the population. For all of human history before about 100 years ago, we were aggressively selected for survival at birth or shortly after. Now, we're not. All those people who would have died might not only suffer other health problems in their life but propagate the "die as a baby" genes to their offspring. Optimistically, it might mean that humans both become dependent on those medical technologies that save babies and mothers, and maintain the capability to provide them so we're fine. It could be a positive direction for evolution, like how we're already adapted to depend on ancient technologies like housing, clothing, and cooking. But maybe it's just bad and future generations will be generally get less and less healthy.

tomthe 3y ago
The head sizes of babies are actually getting larger over the past decades [1]. This might be because of better nutrition, but maybe it is by a large part because we can do caesarean sections in every hospital now and head size is not as limited as it was before anymore. [1]: not the best source, but one I could find now: https://www.tandfonline.com/doi/full/10.3109/07853890.2011.558519 https://www.tandfonline.com/doi/full/10.3109/07853890.2011.5...
- ComputerGuru 3y ago
  The corollary to that is that narrower (maternal) hips are also not being weeded out of the gene pool.
matteoraso 3y ago
I doubt that infant mortality was mostly because of genetics, since natural selection would make it hard for that gene to spread unless there was some other benefit (e.g. how being a carrier for sickle cell anemia is good, even though having sickle cell anemia is bad). The main reason for high infant mortality was probably because of illnesses and famine, not genetic.
- tsimionescu 3y ago
  That's irrelevant to some extent. It still means that those who could better resist illness and famine had a better chance to live, which is likely to have some genetic correlation. Even when the famine is extreme, it still selects for the families cold hearted enough to be able to consciously feed only those who have a chance to survive instead of trying to spread their resources to all their children, which itself may have some genetic source that can be selected by this pressure. Not that either of these are good or necessary for a healthy species, mind you. We will always adapt to our environment and the selective pressures that match it, even when it's one of our own making. If that means fewer children die young, that is an excellent outcome - evolution is never goal oriented anyway.
- EnigmaFlare 3y ago
  It could be partly due to normal harmful random mutations reducing the mother/baby's fitness, which are now being allowed into the gene pool more than before.
- okaram 3y ago
  Yes, but there would still be a very high selective pressure to have more resistance to illnesses and famine.
lm28469 3y ago
I'm more worried about pollution and all the "lifestyle disease" that fuck up our gene pool personally (diabetes, obesity, hormone disruptors, &c.)

tomthe 3y ago

The head sizes of babies are actually getting larger over the past decades [1]. This might be because of better nutrition, but maybe it is by a large part because we can do caesarean sections in every hospital now and head size is not as limited as it was before anymore. [1]: not the best source, but one I could find now: https://www.tandfonline.com/doi/full/10.3109/07853890.2011.558519 https://www.tandfonline.com/doi/full/10.3109/07853890.2011.5...

ComputerGuru 3y ago
The corollary to that is that narrower (maternal) hips are also not being weeded out of the gene pool.

matteoraso 3y ago

I doubt that infant mortality was mostly because of genetics, since natural selection would make it hard for that gene to spread unless there was some other benefit (e.g. how being a carrier for sickle cell anemia is good, even though having sickle cell anemia is bad). The main reason for high infant mortality was probably because of illnesses and famine, not genetic.

tsimionescu 3y ago
That's irrelevant to some extent. It still means that those who could better resist illness and famine had a better chance to live, which is likely to have some genetic correlation. Even when the famine is extreme, it still selects for the families cold hearted enough to be able to consciously feed only those who have a chance to survive instead of trying to spread their resources to all their children, which itself may have some genetic source that can be selected by this pressure. Not that either of these are good or necessary for a healthy species, mind you. We will always adapt to our environment and the selective pressures that match it, even when it's one of our own making. If that means fewer children die young, that is an excellent outcome - evolution is never goal oriented anyway.
EnigmaFlare 3y ago
It could be partly due to normal harmful random mutations reducing the mother/baby's fitness, which are now being allowed into the gene pool more than before.
okaram 3y ago
Yes, but there would still be a very high selective pressure to have more resistance to illnesses and famine.

lm28469 3y ago

I'm more worried about pollution and all the "lifestyle disease" that fuck up our gene pool personally (diabetes, obesity, hormone disruptors, &c.)