Author Topic: Caesarian Births Are Affecting Human Evolution  (Read 1145 times)

Offline Hijiri Byakuren (OP)

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Caesarian Births Are Affecting Human Evolution
« on: December 06, 2016, 01:58:31 AM »
http://www.bbc.com/news/science-environment-38210837

Quote
The regular use of Caesarean sections is having an impact on human evolution, say scientists.

More mothers now need surgery to deliver a baby due to their narrow pelvis size, according to a study.

Researchers estimate cases where the baby cannot fit down the birth canal have increased from 30 in 1,000 in the 1960s to 36 in 1,000 births today.

Historically, these genes would not have been passed from mother to child as both would have died in labour.

Researchers in Austria say the trend is likely to continue, but not to the extent that non-surgical births will become obsolete.

Dr Philipp Mitteroecker, of the department of theoretical biology at the University of Vienna, said there was a long standing question in the understanding of human evolution.

"Why is the rate of birth problems, in particular what we call fetopelvic disproportion - basically that the baby doesn't fit through the maternal birth canal - why is this rate so high?" he said.

"Without modern medical intervention such problems often were lethal and this is, from an evolutionary perspective, selection.

"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."
Opposing forces

It has been a long standing evolutionary question why the human pelvis has not grown wider over the years.

The head of a human baby is large compared with other primates, meaning animals such as chimps can give birth relatively easily.

The researchers devised a mathematical model using data from the World Health Organization and other large birth studies.

They found opposing evolutionary forces.

One is a trend towards larger newborns, which are more healthy.

However, if they grow too large, they get stuck during labour, which historically would have proved disastrous for mother and baby, and their genes would not be passed on.

"One side of this selective force - namely the trend towards smaller babies - has vanished due to Caesarean sections," said Dr Mitteroecker.

"Our intent is not to criticise medical intervention," he said. "But it's had an evolutionary effect. "
Future trends

The researchers estimated that the global rate of cases where the baby could not fit through the maternal birth canal was 3%, or 30 in 1,000 births.

Over the past 50 or 60 years, this rate has increased to about 3.3-3.6%, so up to 36 in 1,000 births.

That is about a 10-20% increase of the original rate, due to the evolutionary effect.

"The pressing question is what's going to happen in the future?" Dr Mitteroecker said.

"I expect that this evolutionary trend will continue but perhaps only slightly and slowly.

"There are limits to that. So I don't expect that one day the majority of children will have to be born by [Caesarean] sections."

Re: Caesarian Births Are Affecting Human Evolution
« Reply #1 on: December 06, 2016, 02:10:07 AM »
Quote from: Hamlet
Despair thy charm;
And let the angel whom thou still hast served
Tell thee, Macduff was from his mother's womb
Untimely ripp'd.

30/1000 to 36/1000 in 50 years is a pretty mild difference, but yeah, looks like more women with a narrow pelvis are giving birth, as are larger babies being born.  It's an interesting shift, but doesn't look like it'd be anything to worry about.

Re: Caesarian Births Are Affecting Human Evolution
« Reply #2 on: December 06, 2016, 03:49:29 AM »
Normal birth has almost been 'made' obsolete here some time ago, because of money. Almost everyone who can afford caeserian and the two day care after it, has it.

It is so often, I only know 1 or 2 women who gave normal birth among dozens and dozens in our community. Not sure about the other communities and different classes. Extreme opposites live together in close quarters.




Offline Atheon

Re: Caesarian Births Are Affecting Human Evolution
« Reply #3 on: December 06, 2016, 06:15:58 AM »
Evilushun? But but but gaaaaaawd crated Adman and Steve in the garden of eatin 600 yers ago.
"Religion is regarded by the common people as true, by the wise as false, and by the rulers as useful." - Seneca

Re: Caesarian Births Are Affecting Human Evolution
« Reply #4 on: December 06, 2016, 06:22:07 AM »
It's not evolution, it's an artifice that isn't sustainable. Without technology to assist the "big heads" will not be able to pass their genes along. At that point the people in the Central African Republic (for example) will carry on without them. This is similar to the English bull dog, whose puppies have heads too big for the birth canal. Remove human assistance and that aberration is kaput.
We 'new atheists' have a reputation for being militant, but make no mistake  we didn't start this war. If you want to place blame put it on the the religious zealots who have been poisoning the minds of the  young for a long long time."
PZ Myers

Re: Caesarian Births Are Affecting Human Evolution
« Reply #5 on: December 06, 2016, 06:45:30 AM »
I find this difficult to believe, since the medical technique to do this and reliably have both mother and child survive has only been around for about  hundred years. Thats a pretty minuscule time frame to effect human evolution.

Also, people with the genes for narrow birth canals have survived to modern times despite millions of years of humanity existing without the benefit of the cesarian section. How did that happen?
And on the wings of a dream so far beyond reality
All alone in desperation now the time has come
Lost inside you\'ll never find, lost within my own mind
Day after day this misery must go on

Re: Caesarian Births Are Affecting Human Evolution
« Reply #6 on: December 06, 2016, 06:59:02 AM »
I find this difficult to believe, since the medical technique to do this and reliably have both mother and child survive has only been around for about  hundred years. Thats a pretty minuscule time frame to effect human evolution.

Also, people with the genes for narrow birth canals have survived to modern times despite millions of years of humanity existing without the benefit of the cesarian section. How did that happen?
It might be due to something like the Sickle Cell Effect. Sickle Cell anemia kills people as they age, but it provides some protection against malaria, so the person doesn't die before they reproduce.
We 'new atheists' have a reputation for being militant, but make no mistake  we didn't start this war. If you want to place blame put it on the the religious zealots who have been poisoning the minds of the  young for a long long time."
PZ Myers

Re: Caesarian Births Are Affecting Human Evolution
« Reply #7 on: December 06, 2016, 07:04:23 AM »
It might be due to something like the Sickle Cell Effect. Sickle Cell anemia kills people as they age, but it provides some protection against malaria, so the person doesn't die before they reproduce.

But as the article states, historically both mother and child would have died in labor without the intervention of the cesarian section. So if both the mother and child with narrow birth canal genes had been getting weeded out of the gene pool for millions of years of human evolution, how are they still with us today?
And on the wings of a dream so far beyond reality
All alone in desperation now the time has come
Lost inside you\'ll never find, lost within my own mind
Day after day this misery must go on

Re: Caesarian Births Are Affecting Human Evolution
« Reply #8 on: December 06, 2016, 07:06:03 AM »
But as the article states, historically both mother and child would have died in labor without the intervention of the cesarian section. So if both the mother and child with narrow birth canal genes had been getting weeded out of the gene pool for millions of years of human evolution, how are they still with us today?
Did it say all women with narrow birth canals died in labor?
We 'new atheists' have a reputation for being militant, but make no mistake  we didn't start this war. If you want to place blame put it on the the religious zealots who have been poisoning the minds of the  young for a long long time."
PZ Myers

Re: Caesarian Births Are Affecting Human Evolution
« Reply #9 on: December 06, 2016, 10:11:48 AM »
But as the article states, historically both mother and child would have died in labor without the intervention of the cesarian section. So if both the mother and child with narrow birth canal genes had been getting weeded out of the gene pool for millions of years of human evolution, how are they still with us today?
Harmful traits aren't necessarily completely weeded out over time.  Plenty of people are biologically infertile for a variety of reasons, and these traits survived from prehistory to modernity.

Offline AllPurposeAtheist

Re: Caesarian Births Are Affecting Human Evolution
« Reply #10 on: December 06, 2016, 11:36:45 AM »
Well! This is a new development..evolution in the making.. I guess in the future women will just have the ability to just sweat babies out into a bowl where they'll develop from egg and sperm to fully grown adults and we can just skip the whole growing up process and at the age of 26 they can begin learning how to roll over on their backs..
OMG! OMG! OMG! Is this something that should keep me awake nights? I'll just have to pass.
« Last Edit: December 06, 2016, 11:38:42 AM by AllPurposeAtheist »
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Offline Baruch

Re: Caesarian Births Are Affecting Human Evolution
« Reply #11 on: December 06, 2016, 07:54:55 PM »
I find this difficult to believe, since the medical technique to do this and reliably have both mother and child survive has only been around for about  hundred years. Thats a pretty minuscule time frame to effect human evolution.

Also, people with the genes for narrow birth canals have survived to modern times despite millions of years of humanity existing without the benefit of the cesarian section. How did that happen?

Traditionally, the mother keeps having babies until she dies in childbirth, then you get a stepmom to raise the orphans ;-(  That is a social adaptation too, that and midwives.  Or you can just be a Russian woman, have the kid while squatting in the potato field, and just sling the baby on top of the potatoes in your sack ;-)
שלום

Offline Baruch

Re: Caesarian Births Are Affecting Human Evolution
« Reply #12 on: December 06, 2016, 07:56:12 PM »
Well! This is a new development..evolution in the making.. I guess in the future women will just have the ability to just sweat babies out into a bowl where they'll develop from egg and sperm to fully grown adults and we can just skip the whole growing up process and at the age of 26 they can begin learning how to roll over on their backs..
OMG! OMG! OMG! Is this something that should keep me awake nights? I'll just have to pass.

They do use artificial wombs in Brave New World.
שלום

Offline pr126

‘War is Peace. Freedom is Slavery. Ignorance is Strength.' 1984

Offline aitm

Re: Caesarian Births Are Affecting Human Evolution
« Reply #14 on: December 08, 2016, 08:39:36 PM »
good stuff, thanks
A humans desire to live is exceeded only by their willingness to die for another. Even god cannot equal this magnificent sacrifice. No god has the right to judge them.-first tenant of the Panotheust