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Obstetrical Dilemma, Pre-Term Birth, And Neanderthals


freeasabird

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I'm always jonesing for more new information on human evolution; it's my favorite branch of science. Recently I stumbled upon some discussion regarding this so called Obstetrical Dilemma which forced a shorter gestational period resulting in human infants being born earlier, and with significantly underdeveloped brains compared to other primates at the same stage. This opens up a whole world of questions to ponder.

  • Could this continuation of evolutionary changes to gestational period, combined with superior diet for modern humans, be a lead cause for increasing 'premature' births? In other words, could premature birth as we now understand it actually be a natural evolutionary change for ever shortening gestational duration?
  • Given enough time to further shorten gestation, could this evolutionary change drive us to extinction?
  • Given that Homo neanderthalis had a larger cranium than Homo sapien (also note the different, less streamlined cranium shape), could it be possible that evolution did not select for them a shorter gestational period and this is how they died out (read: all the mothers and/or infants died in childbirth)?
    • It would be interesting to see studies comparing those in the general population carring Neanderthal DNA with a cross reference to preterm births or other pregnancy complications.

I'd love to hear your thoughts and discussion.

 

 

Some good reading:

 

http://www.scribd.com/doc/37712434/Obstetric-Dilemma -

 

"To alleviate this dilemma, sexual dimorphism occurred, and females’ pelvises became rounder and wider. This caused them to be less efficient at bipedalism, with 9% increased energyexpenditure when running. Shorter gestation times have been selected for resulting in ‘extra-uterine fetuses’ or secondary altriciality, thus causing longer infant dependency in humans (7years versus 4 years in apes).
"

 

 

http://en.wikipedia.org/wiki/Obstetrical_dilemma

 

http://wholewoman.com/blog/?p=999

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I also wanted to add that yet again, the REAL answer for why things are the way they are is so much more interesting than the that suggested by the bible. If there were a god, women have painful childbirth because of the way he chose to make them through evolution, not because of a piece of fruit.

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"Given that Homo neanderthalis had a larger cranium than Homo sapien (also note the different, less streamlined cranium shape), could it be possible that evolution did not select for them a shorter gestational period and this is how they died out (read: all the mothers and/or infants died in childbirth)?"

 

As far as this one goes I don't think it needed to be selected. They were way shorter and wider than sapiens, and im assuming the birth canal was too...but it's totally possible. Maybe their brains got TOO big.

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This is certainly my understanding. This theory definitely makes more sense than the misogynistic fruit theory!

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Guest Babylonian Dream

This is certainly my understanding. This theory definitely makes more sense than the misogynistic fruit theory!

Almost anything, even the crazy "humans are genetically modified apes that were cloned with alien dna" makes more sense than the mysogynistic fruit theory. And that's saying something!

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Bump to see if I can get any responses from those much more scientifically literate than me. I'm particularly interested to know how this affects the future of humanity. Something I read yesterday also alluded to the possibility that in the future cessarian may become a necessity in the majority of births.

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I can only comment on the birth of my two. My wife has broad hips and popped out 3.9kg and 4.1kg babies. Our 1st spent a whole lotta time in the birth canal position and as a result had a head shaped like a water melon before it reverted about a month later to a more round shape.

 

The head is not the issue though, it is the shoulders. Newborns limbs/bones are not as rigid as older kids and I think bone fractures in births are uncommon. Furthermore the cervix parts/dialates to allow for childbirth. (I am thinking pelvis here rather than vaginal)

 

Our second kid 3 years later the birth was easier even though she was bigger, so my wife says.

 

With hospital deliveries, gynies can make adjustments like surgical cuts to prevent tearing of the vulva, our doc did this with both out kids as a precaution.

 

My son came at 38 weeks and my daughter 40 weeks. Rumoured boys are earlier but that is a myth probably.

 

This aspect of evolution has probably changed as we have adapted births to be less threatening. Usually if a woman has narrow hips, docs may recommend C section but I have also seen some docs recommend this as there is more money in C-Sections than natural childbirth.

 

I think at this stage, prem babies are still faced with undeveloped lungs. Gestation would need to be faster and I think for as long as it has been recorded, gestation has been ±40 weeks. It is more the fact that prems are likely to survive if you are in a westernised country with excellent hospitals, Africa in the rural areas, not so much.

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That's interesting LivingLife because I recall my son't shoulders being the same width as his torso at birth, which was smaller than his head. The hard part was getting the head out, then there was break while the doctor had to reach in and get a firm hold of his shoulder to pull (since you obviously can't pull on the head) and then it was all over; out he came. I wonder how much variability there is in this area from one child to the next.

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This certainly interest me as my favorite thing to study is evolution and I think this theory makes quite a bit of sense. I think the Neanderthals would be done for any way if this was the case because having larger bodies at birth would have been good to fend off the cold but with smaller bodies infant mortality rates would of probably gone up just as much because of the weather, harsh climate for a premature birth babay to survive in.

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That's interesting LivingLife because I recall my son's shoulders being the same width as his torso at birth, which was smaller than his head. The hard part was getting the head out, then there was break while the doctor had to reach in and get a firm hold of his shoulder to pull (since you obviously can't pull on the head) and then it was all over; out he came. I wonder how much variability there is in this area from one child to the next.

There is of course that hole in the skull that also allows the softer bone of the skull to adapt. Like I said my first kids head was like a water melon and was FUGLY but it changed quite rapidly.

 

Is the birth position of the woman on her back natural? Perhaps a squatting position would be more conducive as then you have gravity helping. Wendyshrug.gif

 

At the end of the day, newborns are still very vulnerable compared to say a buck that stands up pretty quickly.

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At the end of the day, newborns are still very vulnerable compared to say a buck that stands up pretty quickly.

 

That's an interesting point and I was about to bring it up. I remember reading (not sure if it was here or elsewhere) that all humans are essentially born premature even if carried to full term. Cattle, deer, and other mammals are walking and exploring the environment hours after birth but with humans it takes much longer. The reason for that is if humans reached that level of development prior to birth, they would be much too large to be born and extinction would be inevitable. Think of how much larger a 1-2 year old (roughly equivalent level of development since most are able to walk and interact at that age) is than a newborn. Also, IIRC no other mammal (not even other primates) delays adolescence for 13-14 years like humans do. The brain and body simply take that long to develop, which would be a serious liability in a hostile environment. The brain isn't even fully mature until the early 20s.

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  • 2 weeks later...

Is the birth position of the woman on her back natural? Perhaps a squatting position would be more conducive as then you have gravity helping. Wendyshrug.gif

 

That somehow reminded me of...

 

 

fucking PLOP

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