Non-natural childbirth, vaccines

[daniel6874]

Two related questions.

First, could C-sections and surgically-assisted births create a growing subset of the population who cannot survive "natural" childbirth?

Second, the CDC and other sites list over 30 recommended vaccines. In the same vein as question above, could this give rise over time to a subset of the population who could not survive without a battery of immunizations?

We all know the benefits of modern obstetrics and (some) vaccines. My question is about possible unintended longterm consequences--a distant future in which access to medicine is suddenly limited, for example.

 

[Kerrie]

Two related questions.

First, could C-sections and surgically-assisted births create a growing subset of the population who cannot survive "natural" childbirth?

Second, the CDC and other sites list over 30 recommended vaccines. In the same vein as question above, could this give rise over time to a subset of the population who could not survive without a battery of immunizations?

We all know the benefits of modern obstetrics and (some) vaccines. My question is about possible unintended longterm consequences--a distant future in which access to medicine is suddenly limited, for example.

If a woman is unable to deliver children without surgical assistance, that doesn't mean her offspring will have the same issues because of the genes from the father. Also, the surgical assistance might be saving the life of the mother more than the child in some instances.

I think the vaccine discussion should be started in a new thread.

 

[ABioTeacher]

The same question could be posed for any number of genetic defects that we can treat. (for example: poor eye sight or diabetes)

Human ability to mask or compensate for set backs that 13,000 years ago would have meant death or decreased chance of offspring, does have an significant impact on the prevalence of these traits in the population today. Good or bad...it is what it is.

While a mother who delivers via c-section is likely to have a daughter that does the same, what difference does it make if we have the capability to preform the delivery?

As for the vaccines...becoming infected by measles does not mean you had a weak immune system. Viruses and other diseases causing agents that we vaccinate against attack indiscriminately. We are not increasing a particular trait for weak immunity by vaccinating an average child that may or may not have died from some disease in an age before vaccines. All we are doing is combating a natural predator of the human species. Therefore we are limiting it's effect on population growth and not genetic strength.

On a related note, just because your parents had a strong immune system and survived a disease does not mean you will. This is because each person develops their immune system in a very complex manner that involves the recombination and splicing of several genes. Each person has unique antibodies etc...The only way vaccination would have an impact is by allowing genetically immune suppressed individuals to procreate. Unfortunately, for the severely suppressed individuals there are many other diseases (without vaccinations) that are ready and waiting to attack their immune system.

This question also borders along the lines of picking who should reproduce...genetic cleansing so to speak...And even that wouldn't work because there are numerous agents of disease or environmental factors that can alter an individuals fitness level.

I suggest the movie Gattica.

 

[D H]

My question is about possible unintended longterm consequences--a distant future in which access to medicine is suddenly limited, for example.

You are implicitly positing a rather large calamity here. If access to medicine is suddenly limited, inability to perform C sections or give measles vaccines will be the last of humanities worries.

 

[GreatEscapist]

Answer to first:

No, that wouldn't affect the kid's ability to bear children naturally. It won't affect the child in that way.

I concur that the second question be a new thread- it's a looong discussion.

 

[Borek]

Actually... number of woman that have problems getting pregnant, number of ednangered pregnancies, number of kids with birth deficits - all these grow. It is not related ONLY to C-sections and surgically-assisted births, but I don't think there is any doubt these are effects of our earlier medical "succeses". Each next generation is weaker than the previous one, as more and more kids that earlier were eliminated from the population are now able to survive till their own procreation age.

Whether it is good or bad - I don't know, but I have no doubts this process exists.

 

[daniel6874]

You are implicitly positing a rather large calamity here. If access to medicine is suddenly limited, inability to perform C sections or give measles vaccines will be the last of humanities worries.

This was an interesting reply. As some replies noted, not all problems addressed by (say) surgically-assisted births and (some) vaccines are heritable. So it would take a long time for a vulnerable subset to emerge. Once it emerged, the medicine we take for granted could easily erode over a century into something less dependable (there are places in the world now where safe OB services are nonexistent, nevermind vaccines). So it need not be a catastrophe, just a gradual diminution of quality and availability.

And no I am not suggesting we deny medical services to anyone. I am wondering about an eventuality that I hope is purely academic.

 

[Shalashaska]

This was an interesting reply. As some replies noted, not all problems addressed by (say) surgically-assisted births and (some) vaccines are heritable. So it would take a long time for a vulnerable subset to emerge. Once it emerged, the medicine we take for granted could easily erode over a century into something less dependable (there are places in the world now where safe OB services are nonexistent, nevermind vaccines). So it need not be a catastrophe, just a gradual diminution of quality and availability.

And no I am not suggesting we deny medical services to anyone. I am wondering about an eventuality that I hope is purely academic.

Lets say that Borek is 100% right, for the sake of argument. If the catastrophe D H wisely mentions were to occur, I suspect that adaptations related to child-bearing would not be the issue. Remember that most of the world doesn't enjoy such medical luxuries so freely. Our "weak" and "strong" stock, if you like to think of it that way, are all increasing, and in a disaster it would rapidly decrease. If such a disadvantageous change occurred, I believe that it would be eliminated rapidly. After all, as you posit a block to healthy reproduction, those people would be dwarfed by those who could bear children. I doubt that something so critical in the history of our evolution could be wiped away by surgical procedures.

In the end, this is a bit of "if I cut a notch in the mother or father's ear, does the child inherit it?" Besides, quality and access to medicine is generally improving. Why would you assume the future holds diminishing technology?

 

[russ_watters]

You are implicitly positing a rather large calamity here. If access to medicine is suddenly limited, inability to perform C sections or give measles vaccines will be the last of humanities worries.

There's a thread in the tech forum about protecting hard drives and flash drives from EMP. Same principle applies: If someone hits us with an EMP strong enough to fry a flash drive (if that's even possible), I'm going to be far too preoccupied with having lost every electronic device I run across in daily life to worry about what was on the flash drive!

But yes, certainly these things can all factor into evolution. If a woman has narrow hips and as a result has trouble giving birth and has a C-section, that's a trait she may pass on to her offspring that could have killed her and her child during labor. Clearly, this alleviates an evolutionary pressure.

 

[daniel6874]

Lets say that Borek is 100% right, for the sake of argument. If the catastrophe D H wisely mentions were to occur, I suspect that adaptations related to child-bearing would not be the issue. Remember that most of the world doesn't enjoy such medical luxuries so freely. Our "weak" and "strong" stock, if you like to think of it that way, are all increasing, and in a disaster it would rapidly decrease. If such a disadvantageous change occurred, I believe that it would be eliminated rapidly. After all, as you posit a block to healthy reproduction, those people would be dwarfed by those who could bear children. I doubt that something so critical in the history of our evolution could be wiped away by surgical procedures.

In the end, this is a bit of "if I cut a notch in the mother or father's ear, does the child inherit it?" Besides, quality and access to medicine is generally improving. Why would you assume the future holds diminishing technology?

You are not reading carefully. (1) I pointedly said that many of the problems addressed by surgery were not heritable, and not part of the issue I raised. Precisely the "notched ear" issue. (2) I did not suggest that this problem would be universal, and I already noted that medical care is substandard in many places. You repeat this. (3) I made no assumptions about the future. If our history as a species goes back more than 400,000 years, then most of our history has taken place in the absence of surgery. A better question would be, why would anyone assume it's here to stay?

 

[Shalashaska]

You are not reading carefully. (1) I pointedly said that many of the problems addressed by surgery were not heritable, and not part of the issue I raised. Precisely the "notched ear" issue. (2) I did not suggest that this problem would be universal, and I already noted that medical care is substandard in many places. You repeat this. (3) I made no assumptions about the future. If our history as a species goes back more than 400,000 years, then most of our history has taken place in the absence of surgery. A better question would be, why would anyone assume it's here to stay?

The portions in bold seem contradictory, and while Homo Sapiens Sapiens may have been extant for 400,000 years, we have millions of years from previous species all of which birthed via the pelvic girdle. In a future without C-Sections or other means to alleviate childbirth, we'd have a higher mortality rate, and those people unable to bear children... would be gone from the gene pool. Alleviating an evolutionary pressure by making it invisible to selection for a while for some, isn't the same as changing humanity radically. You asked if this was likely to produce a subset which cannot survive, but factors involved in childbirth are myriad.

As long as a significant portion of men find typically female hips and buttocks (shaped by the hips) to be attractive, that is a bigger factor than the mother or child surviving. Assuming nothing about the future, loss of the ability to perform a C-Section would require a LOT of damage to human knowledge. A copper or bronze knife, some alcohol and sinew, and something to act as a few clamps (including midwives' hands) and KNOWLEDGE are enough to perform a C-Section. You're not going to have a good time of it, and you may well kill the mother, but that wouldn't change the male desire to impregnate them, and that's more in the lines of real evolution than (what you believe) is a transient surgery.

 

[Borek]

As long as a significant portion of men find typically female hips and buttocks (shaped by the hips) to be attractive, that is a bigger factor than the mother or child surviving. (...) that wouldn't change the male desire to impregnate them, and that's more in the lines of real evolution than (what you believe) is a transient surgery.

I can be misreading you, but if you mean that woman that is not physically attractive have no chances of finding a male, I am sure you are wrong. Chances of a non attractive male to not pass his genes are orders of magnitude higher than chances of non attractive female. Males in reproductive age are much less choosy and will make sex with everything that moves. Those less fortunate have problems finding partners, as sex is privilege of alpha males. This is skewed in monogamous society, but even in monogamous society dying a virgin is rarely forced by lack of occasions. So from the evolutionary point of view attractiveness of female is much less important than her ability to give birth and surviving.

 

[Shalashaska]

I can be misreading you, but if you mean that woman that is not physically attractive have no chances of finding a male, I am sure you are wrong. Chances of a non attractive male to not pass his genes are orders of magnitude higher than chances of non attractive female. Males in reproductive age are much less choosy and will make sex with everything that moves. Those less fortunate have problems finding partners, as sex is privilege of alpha males. This is skewed in monogamous society, but even in monogamous society dying a virgin is rarely forced by lack of occasions. So from the evolutionary point of view attractiveness of female is much less important than her ability to give birth and surviving.

I'm not talking about someone who is considered ugly by a cultural standard. There are features which are universally attractive to one degree or another. The buttocks, breasts, face, all play a role in this. My point isn't that any kind of man or woman can't get sex if they want it, but I feel this assures that women with regular features and typically female pelvis will be unlikely to change as they don't NEED to compete given the population. Now, China might be an example where competition for women is fierce, but again, all of this has to assume a return to barbarism in a VERY short period of time.

A it's not enough to remove an evolutionary pressure, if there is also an ADVANTAGE conferred by looks. Remember, we find regular features and signs of health attractive for a reason: they indicate a higher likelihood of producing healthy offspring. I'm not talking about supermodels or the like, just healthy regular features that are feminine. Removing a hindered with a surgery, vs. the advantage. I'd need to see evidence of a narrowing pelvis in women correlated with C-Sections before I even entertained the notion that this creates a stable sub-set within a population.

Given that we reproduce sexually, even a woman with a narrow birthing canal is is only contributing 50% of the genetic material. This also ONLY would apply to those C-Sections for women who have that as an issue, which ISN'T typical. The need for a C-Section is usually:

1: Positioning of the baby
2: Time in labor
3: Bleeding
4: Fetal distress
5: BP or other systemic issues without a clear cause
6: Vanity (not a judgment, just a term of art)
7: Inability to give birth unassisted.

Remember that a C-Section generally puts a woman at risk for miscarriage in the future as well, which would also seem to keep such a population limited. Instead of the implicit doom of the OP, advancing medicine may also be able to predict such issue. Regardless, most of those causes have nothing to do with the biology of the woman's pelvis, uterus, but are just nasty chance.

 

[hamster143]

But yes, certainly these things can all factor into evolution. If a woman has narrow hips and as a result has trouble giving birth and has a C-section, that's a trait she may pass on to her offspring that could have killed her and her child during labor. Clearly, this alleviates an evolutionary pressure.

There's a fundamental theorem in genetics that essentially predicts that traits that are important for fitness tend to have low heritability, and vice versa. Since hip width in a female has been a highly important fitness trait for hundreds of thousands of years (if your hips are too narrow, you won't procreate), it wouldn't be heritable.

That also goes to the whole argument against c-sections and vaccines. We don't have to worry too much about "weakening" the humankind. One caveat is destructive mutations. It could be argued that we should try to discourage people with severe destructive aberrations in their genome (e.g. Down's syndrome) from reproducing. Or at least try to make sure that they don't reproduce at a higher rate than healthy humans.

 

[Borek]

tend to have low heritability

wouldn't be heritable.

These are not exactly compatible statements.

 

[hamster143]

These are not exactly compatible statements.

Why? Zero heritability is a limiting case of low heritability.

 

[Evo]

There's a fundamental theorem in genetics that essentially predicts that traits that are important for fitness tend to have low heritability, and vice versa. Since hip width in a female has been a highly important fitness trait for hundreds of thousands of years (if your hips are too narrow, you won't procreate), it wouldn't be heritable.

It's not the width of the hips, I have very narrow hips and gave birth to both of my children vaginally with no problems. During the pregnancy, the cartilage that holds the pelvic bones together softens and spreads apart, this allows a wider opening for the baby.

 

[Kerrie]

It's not the width of the hips, I have very narrow hips and gave birth to both of my children vaginally with no problems. During the pregnancy, the cartilage that holds the pelvic bones together softens and spreads apart, this allows a wider opening for the baby.

The same happened with me thankfully, but does it happen for all women?

 

[hamster143]

It's not the width of the hips, I have very narrow hips and gave birth to both of my children vaginally with no problems. During the pregnancy, the cartilage that holds the pelvic bones together softens and spreads apart, this allows a wider opening for the baby.

There's a limit to how far they'll go. This limit could be genetic (not saying that it is, but it might be). My wife was unable to give birth to our son vaginally because he simply couldn't fit through the opening. Back in the old days before asepsis and antibiotics, that likely would've meant death for the mother, the baby, or both.

 

[Evo]

The same happened with me thankfully, but does it happen for all women?

It's the release of a hormone called, of all things, Relaxin, it should happen, unless something is wrong.

 

[lisab]

It's the release of a hormone called, of all things, Relaxin, it should happen, unless something is wrong.

Yes and it's also the reason our feet get a bit bigger during pregnancy. The hormone stretches out all cartilage in the body, not just in the hips.

 

[Moonbear]

There's a fundamental theorem in genetics that essentially predicts that traits that are important for fitness tend to have low heritability, and vice versa. Since hip width in a female has been a highly important fitness trait for hundreds of thousands of years (if your hips are too narrow, you won't procreate), it wouldn't be heritable.

Actually, that's not true. Pelvic shape/diameter is heritable, and there are some racial differences in pelvic diameter as well. These are differences are used in forensics to help identify the race of skeletal remains, and are also well known among obstetricians. For example, a caucasian woman would have a rounder pelvis, while an Asian woman would have a more oval shaped pelvis. Correspondingly, Asian babies are usually born with smaller head diameters that fit through these smaller pelvises. Obstetricians need to be aware of this, because a child born to an Asian woman with a caucasian father may have difficulty being born naturally if the baby's head size is of a more caucasian size.

However, this does not mean that the child would have the same difficulties as the mother. Afterall, the same genetic mix that left the baby with the large head may also contribute to her having more caucasian pelvic traits as well. So, this is really only a first generation mixed race problem, and not something that would persist over generations with more genetic mixing.

And, of course other factors aside from genetics can influence things like pelvic diameter and baby's birth size. Nutrition is one factor, both from a perspective of undernutrition of a mother when she was young influencing her growth vs overnutrition while pregnant leading to an unusually large birthweight baby. Another issue would be prior injury. If a woman had a pelvic fracture at some time in her life prior to childbirth, this too could affect her pelvic diameter.

There are other reasons babies are delivered by C-section that have nothing to do with genetics. Many are born that way for convenience, and have nothing to do with ability to have a natural birth. Some are performed to avoid exposing the newborn to sexually transmitted diseases during a vaginal delivery (for example, a woman with herpes simplex II would be advised to have a c-section to avoid exposing the baby to herpes during delivery). Many are to deliver a breech baby.

So, there are both genetic and non-genetic factors that may contribute to the need for a C-section, but even in the case of genetic factors, it doesn't mean they will be an issue for the offspring.

 

[AnaShep]

I think it would be less of the width of the hips and more of the size of a baby. A woman giving birth to a 10lb baby is more likely to have more 10lb babies. When these children grow up, they too are likely to have larger babies.

I have yet to meet a woman who could give birth to a 10+lb baby naturally. Therefore, I would contend a genetic predisposition to have large babies could effect the population if c-sections were suddenly cut out.

 

[Eslocklier]

I don't think its the least bit debatable that modern medical technology (as well as legal disclaimers, safety equipment, etc), in many forms, have circumvented the forces of evolution and resulted in a weakened human race. It is not limited to these two instances.

 

[Evo]

I think it would be less of the width of the hips and more of the size of a baby. A woman giving birth to a 10lb baby is more likely to have more 10lb babies. When these children grow up, they too are likely to have larger babies.

I have yet to meet a woman who could give birth to a 10+lb baby naturally. Therefore, I would contend a genetic predisposition to have large babies could effect the population if c-sections were suddenly cut out.

I'm between 5'2"-5'3", and was very thin with 28 inch hips with both of my children. My second daughter was 9 pounds 6 ounces when she was born and I gave birth vaginally with no problems. She was 21 inches long, so a sturdy baby, her sister was also 21 inches, but only 7 pounds, I could have easily delivered a 10 pound baby, especially if it was longer, and I have a very petite frame.

Do you have a peer reviewed scientific paper showing that women with an average size pelvis would have trouble delivering a 10 pound baby? You need to post one. As Moonbear said, it's the size of the head and whether the baby is breech that usually determines the need for a C-section.

 

[JaredJames]

While a mother who delivers via c-section is likely to have a daughter that does the same, what difference does it make if we have the capability to preform the delivery?

Interesting late night read.

I'm curious if there is anything to back this up? I don't know whether or not it's true, but it sounds a bit off to me. We seem to be ignoring any genetic input from the father and assuming it wasn't the childs father which created the need for a c-section in the first place (referring to the asian/caucasian mixed discussed above).

 

[Evo]

Interesting late night read.

I'm curious if there is anything to back this up? I don't know whether or not it's true, but it sounds a bit off to me. We seem to be ignoring any genetic input from the father and assuming it wasn't the childs father which created the need for a c-section in the first place (referring to the asian/caucasian mixed discussed above).

No, it's not true, Moonbear addressed that already.