4 ms·

Huh, TIL that childbirth was likely challenging for other smaller-head hominids, not just big-brain Sapiens. Walking upright is still the strongest hypothesis

by kortex 4y ago

Huh, TIL that childbirth was likely challenging for other smaller-head hominids, not just big-brain Sapiens. Walking upright is still the strongest hypothesis for the difficult birth process. https://scitechdaily.com/scientists-have-figured-out-why-childbirth-became-so-complex-and-dangerous/ https://scitechdaily.com/scientists-have-figured-out-why-chi...

svnt 4y ago
There is a very large difference between was and is, here. Human childbirth at this point is almost certainly a result of positive selection, not an “evolutionary accident.” A “difficult birth process” has been played up in popular media. In the vast majority of cases, childbirth successfully exits a child, and also preserves the mother. There is some evidence that the mechanics of this process were better before early Western medicine’s gynecological “expertise”. The whole thing stems from inaccurate, sexist attempts from the 20th century to explain why women are generally athletically not as capable as men.
robocat 4y ago
> All of this shows how human birthing is much more difficult and painful than that of large apes. Sounds logical and commonly beleived, however I had trouble finding any papers to actually support that humans have more maternal deaths. A 2018 paper[1] says “The observations by Yeligulashvili, representing cumulative data on over 200 births spanning a 16 year period in the Sukhumi nursery, remain one of the largest reports documenting labor in NHP [non-human-primates]”. The paper about Baboons also said “there were 1021 cesarean deliveries, 5195 vaginal deliveries”, which either implies that the veterinarians are very often worried about the survival of the Baboon mother, or that the veterinarians perform cesarean deliveries for other reasons (like humans do). There are strong evolutionary pressures against a mother’s death during parturition, which leaves one wondering what the other evolutionary compromises are that result in maternal death. The survival of a baby mostly trumps the needs of a mother for passing on genes (a gene where a child lives to breed has a very strong selection pressure), so that probably is one major reason. If human societies have brought up maternal death orphans for many many generations, then maternal deaths should become more common? [1] https://www.nature.com/articles/s41598-018-19221-4 https://www.nature.com/articles/s41598-018-19221-4
- svnt 4y ago
  > The survival of a baby mostly trumps the needs of a mother for passing on genes (a gene where a child lives to breed has a very strong selection pressure), so that probably is one major reason. This is generally not true for species that take a long time to reach reproductive maturity, and more so if they evolve to become physically underdeveloped at birth. A (proven) fertile human female is reproductively much more valuable than a newborn.
  - robocat 4y ago
    Yeah, on second thoughts you are right because I hadn’t thought about what happens to the mothers that lack the gene. If there are genes that kill mothers, the child has the chance to pass on the gene, which is a strong selection pressure for the child. However meanwhile mothers without that gene will have more babies, so the selection pressure is mostly whether the mother has the gene or not, because mothers without the gene will have more descendants. It’s difficult to think through realistic examples, and probabilities.
    - svnt 4y ago
      Yeah there is a lot of complexity to the process. Other things to consider include that if the child’s genes kill the mother they generally do this by causing the child to fail to exit the mother, which also kills the child. The exception to this would mostly be genes that result in the mother’s death from blood loss, after the child had exited, so related to placental issues/placement. But for this to succeed for the child it also assumes someone else would care for the child as well as the mother would have, which is unlikely at best.

by kortex 4y ago

svnt 4y ago

There is a very large difference between was and is, here. Human childbirth at this point is almost certainly a result of positive selection, not an “evolutionary accident.” A “difficult birth process” has been played up in popular media. In the vast majority of cases, childbirth successfully exits a child, and also preserves the mother. There is some evidence that the mechanics of this process were better before early Western medicine’s gynecological “expertise”. The whole thing stems from inaccurate, sexist attempts from the 20th century to explain why women are generally athletically not as capable as men.

robocat 4y ago

> All of this shows how human birthing is much more difficult and painful than that of large apes. Sounds logical and commonly beleived, however I had trouble finding any papers to actually support that humans have more maternal deaths. A 2018 paper[1] says “The observations by Yeligulashvili, representing cumulative data on over 200 births spanning a 16 year period in the Sukhumi nursery, remain one of the largest reports documenting labor in NHP [non-human-primates]”. The paper about Baboons also said “there were 1021 cesarean deliveries, 5195 vaginal deliveries”, which either implies that the veterinarians are very often worried about the survival of the Baboon mother, or that the veterinarians perform cesarean deliveries for other reasons (like humans do). There are strong evolutionary pressures against a mother’s death during parturition, which leaves one wondering what the other evolutionary compromises are that result in maternal death. The survival of a baby mostly trumps the needs of a mother for passing on genes (a gene where a child lives to breed has a very strong selection pressure), so that probably is one major reason. If human societies have brought up maternal death orphans for many many generations, then maternal deaths should become more common? [1] https://www.nature.com/articles/s41598-018-19221-4 https://www.nature.com/articles/s41598-018-19221-4

svnt 4y ago
> The survival of a baby mostly trumps the needs of a mother for passing on genes (a gene where a child lives to breed has a very strong selection pressure), so that probably is one major reason. This is generally not true for species that take a long time to reach reproductive maturity, and more so if they evolve to become physically underdeveloped at birth. A (proven) fertile human female is reproductively much more valuable than a newborn.
- robocat 4y ago
  Yeah, on second thoughts you are right because I hadn’t thought about what happens to the mothers that lack the gene. If there are genes that kill mothers, the child has the chance to pass on the gene, which is a strong selection pressure for the child. However meanwhile mothers without that gene will have more babies, so the selection pressure is mostly whether the mother has the gene or not, because mothers without the gene will have more descendants. It’s difficult to think through realistic examples, and probabilities.
  - svnt 4y ago
    Yeah there is a lot of complexity to the process. Other things to consider include that if the child’s genes kill the mother they generally do this by causing the child to fail to exit the mother, which also kills the child. The exception to this would mostly be genes that result in the mother’s death from blood loss, after the child had exited, so related to placental issues/placement. But for this to succeed for the child it also assumes someone else would care for the child as well as the mother would have, which is unlikely at best.