Caesarean births 'affecting human evolution'
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Re: Caesarean births 'affecting human evolution'
#2Main stream journalists can not get science right.
In the normal course of evolution women with narrower pelvis die a painful death while delivering a baby (or the baby dies). Thus the genes that give women a narrower pelvis do not get passed on.
We can not let these women die this horrible death. This is a good outcome.
Re: Caesarean births 'affecting human evolution'
#3It is blindingly obvious from an evolutionary standpoint that this is happening. I have thought about it a fair bit, as it has directly impacted my own family, and I've no doubt it will continue to do so in subsequent generations.
I don't think it's something to worry much about, as the much broader benefits of modern medicine (namely, antibiotics) have had so much impact on our survival rate that this would pale into insignificance.
Which may be borne out (pun intended) by the numbers: 3% to 3.3% or 3.6% in 50-60 years - is that statistically significant? The error there is in the same order as the overall increase, so it's hard to believe it's even measurable at this stage.
Because it is so obviously going to happen, I suspect there may be some curve-fitting going on here?
Re: Caesarean births 'affecting human evolution'
#4Main stream journalists can not get science right. In the normal course of evolution women with narrower pelvis die a painful death while delivering a baby (or the baby dies). Thus the genes that give women a narrower pelvis do not get passed on. We can not let these women die this horrible death. This is a good outcome.
"Women with a very narrow pelvis would not have survived birth 100 years ago. They do now and pass on their genes encoding for a narrow pelvis to their daughters."
and
"Our intent is not to criticise medical intervention," he said. "But it's had an evolutionary effect."
The article said everything you said, and more, in what way did it "not get science right"?
Re: Caesarean births 'affecting human evolution'
#5Main stream journalists can not get science right. In the normal course of evolution women with narrower pelvis die a painful death while delivering a baby (or the baby dies). Thus the genes that give women a narrower pelvis do not get passed on. We can not let these women die this horrible death. This is a good outcome.
There's two sides to this coin. By allowing normally lethal genes to be passed on were likely to cause more death in the future. This is definitely something that should be screened and prevented, whether through gene editing, surrogacy, or just selecting for embryos that are either male or lack the undesired trait.
Nobody has to die to voluntarily select this out of the population. The Jewish community has been on the forefront of this for a long time. On the border of eugenics I guess, but self selecting against genes that will cause suffering or death.
Re: Caesarean births 'affecting human evolution'
#6Main stream journalists can not get science right. In the normal course of evolution women with narrower pelvis die a painful death while delivering a baby (or the baby dies). Thus the genes that give women a narrower pelvis do not get passed on. We can not let these women die this horrible death. This is a good outcome.
To be fair, aside from the preschool formatting of the article (one sentence per paragraph, a concerning recent BBC trend), the journalist didn't actually say anything incorrect.
But she did not answer the main question that was asked: why the human pelvis has not grown wider over the years? She said that there were two opposing forces, one for larger babies (they have more chance of survival), and the other was natural selection preventing them getting too large (by killing them both in childbirth).
Maybe I'm missing something, but neither of those answer the question of why the pelvis has not got larger.
All I can assume is that it is (a) an evolutionary trend of men to be attracted to younger and potentially, on average, slimmer and more healthy or fertile women, and (b) cultural, since there is evidence that in historic times and possibly also in less technologically advanced societies, larger hips are considered desirable (which makes total sense in a society with no access to modern medicine).
I'm sure some anthropologists will beat me up for these terrible generalisations, but in general, on average, it seems these forces may have an impact on pelvis size over generations?
Re: Caesarean births 'affecting human evolution'
#7> Historically, these genes would not have been passed from mother to child as both would have died in labour.
How do we know that? As the name implied, Caesar was born this way, a little over 2000 years ago. It's likely the procedure is much much older, too. So what timeframe are we talking about?
What we didn't know how to do 100 years ago was how to save mother and child once birth had begun and the baby's head had started to go into the canal and got stuck. But humanity have known how to do caesarean birth for a very long time (there are even cases of women doing it to themselves).
Also, from an evolutionary perspective it doesn't matter if the mother survives birth; it only matters whether the baby lives. So it's at best incorrect to phrase the problem this way:
> Women with a very narrow pelvis would not have survived birth 100 years ago. They do now and pass on their genes encoding for a narrow pelvis to their daughters.
Re: Caesarean births 'affecting human evolution'
#8Evolution is a ultimate rat race.
FYI offtopic: Kid can be mingled in umbilical cord and natural birth is not possibile then. Only way is caesarean. Dont pull the baby by the head.
Re: Caesarean births 'affecting human evolution'
#9Main stream journalists can not get science right. In the normal course of evolution women with narrower pelvis die a painful death while delivering a baby (or the baby dies). Thus the genes that give women a narrower pelvis do not get passed on. We can not let these women die this horrible death. This is a good outcome.
To be fair, aside from the preschool formatting of the article (one sentence per paragraph, a concerning recent BBC trend), the journalist didn't actually say anything incorrect. But she did not answer the main question that was asked: why the human pelvis has not grown wider over the years? She said that there were two opposing forces, one for larger babies (they have more chance of survival), and the other was natu…
Men are indeed attracted to relatively wide-hipped women, but there is an upper limit on hip width. There is a biomechanical tradeoff between pelvic shape and locomotor efficiency. The width of the pelvis affects the energy needed for a bipedal gait, since it alters the shape of the largest bones of the lower skeleton and their associated musculature (compare the angle of the femur in men v women and imagine how it affects joint stress). So there's a three way evolutionary arms race between the needs of the large-brained infant, the need to successfully expel said infant, and the need to be able to walk and run efficiently and without musculoskeletal damage.
Re: Caesarean births 'affecting human evolution'
#10> Historically, these genes would not have been passed from mother to child as both would have died in labour. How do we know that? As the name implied, Caesar was born this way, a little over 2000 years ago. It's likely the procedure is much much older, too. So what timeframe are we talking about? What we didn't know how to do 100 years ago was how to save mother and child once birth had begun and the baby's head ha…
> Also, from an evolutionary perspective it doesn't matter if the mother survives birth; it only matters whether the baby lives.
Wouldn't it though? A mother that lives can go on to give birth to more children.
Not to mention that a mother's survival might affect her child's chance of survival.