I’m putting this thread in here because I believe that a lot of answers may very well be theoretical. If I thought there was a ton of evidence one way or the other, I would have put this in GQ. Then again, maybe I’m wrong.
The other day, I was talking to a friend of mine about his sister who, after 5+ years of trying and miscarriages, conceived twins through IVF. She definitely has two beautiful babies that are the light of her life, but that isn’t really what I’m curious about.
I’ve read articles here and there that talk about how the common use of C-Sections is breeding women with increasingly narrow hips (no, I don’t have a cite. If I’m wrong, feel free to show me. This is just something from memory). It seems that we are, quite naturally speaking, weakening our gene pool in that regard.
So the natural thought progression for me is to wonder if IVF is following us down a similar road. So, I’m curious about opinions regarding IVF and genetics. By doing in a lab what nature does not want to do, are we creating people with very weak genes (genes that naturally would never have come together)? Does this have any long term implications?
Just curious and bouncing some ideas around the smartest bunch around.
Nope; given that humans have long generation times, successful C-sections are historically recent, and that C-sections are nowhere near universal, there simply hasn’t been enough time and evolutionary pressure for such selective breeding.
Again, no. The problem is that most or all technologically based evolutionary pressure on humans changes too fast to have a significant efffect, given our long generations. Long before any “weak” genes or “narrow hip” genes can have any real effect on the population, either some other technology will be used, or genetic therapy will simply eliminate the defective genes.
C-sections: women now have huge children compared to what they used to - but our hips haven’t changed. Change a pregnant woman’s diet and you’ll be back to the five and six pound babies are bodies are meant to deliver.
IVF:
While I have some concerns about parental age and genetics (both mother and father), and older parents who do IVF - in a lot of cases IVF is making up not for bad genes (which wouldn’t work in natural conception or in a petri dish) but for scarred fallopean tubes or endometriosis. Scarred fallopean tubes are not genetic. Endo may be - but its not a huge weakening of the gene pool to not select out of “horrible cramping once a month.”
We’ve been doing that ever since we started making medicine actually work and helping people survive to breeding age instead of dying from the ton of health issues that we used to experience.
Do you have a cite for that? I seem to recall that babies born in the early part of this century were huge because doctors believed it was healthy to fatten up pregnant women.
My wife is 5 feet nothing and 100 lbs. She had both of our children, totally natural birth, no drugs no surgeries, and both were between 7 and 8 pounds. AFAIK that’s a fairly normal birth weight for a child. It’s about the weight I was when I was born, as well as my four siblings, all of us born between 1961 and 1972. Most kids that I’ve heard of born full term in the past ten years have been between 6 and 9 pounds.
Surgery does not change one’s genes. Maybe I’m missing something in your train of thought, but I can’t see how a woman who gives birth by C-section is more likely to have narrow-hipped daughters.
I think the reasoning is that a narrow-hipped woman and her first offspring would have been more likely to die in childbirth before c-sections, and their “narrow-hipped genes” wouldn’t be passed on down the family tree. Frankly, I see the logic here, and I’m not so quick to dismiss the genetic implications of IVF and heroic measures in the delivery room.
Granted, much IVF is done on older women trying to conceive for the first time, so the damage to their ova is due to time, not genetics. But older eggs do have more genetic “mistakes” which - years ago when no one would give birth at 50+ years old - wouldn’t have been passed on. So how can we not be having more genetically damaged babies now that we can and do bring forth and save genetically damaged babies?
The notion is not that it’s selective breeding… it’s that, because women with narrow hips and their children are not dying as much as they used to, there’s a higher amount of them around.
So, sort of “the selective dying got switched off”.
Okay, **Nava ** and WhyNot, I understand your reasoning now. What I don’t have is any evidence that the average woman’s pelvis is narrower than, say, 50 years ago. As ShibbOleth pointed out, slim-hipped women have been have babies naturally for a long time. The pelvis spreads apart in a way that I don’t really understand.
I’m neither a doctor nor do I play one on TV, but my WAG would be that we won’t know what, if any, effects modern medicine is going to have on the over all gene pool for a few thousand years at least. We’ve only been able to do much of this stuff successfully for less than a century (or so…not sure when C-Sections became both common and relatively safe) after all…no way in hell this is having an effect today in passing the ‘narrow-hip gene’ widely among the pool. Even the effects of better medicine aren’t having much of an effect yet on OUR gene pool, because as Der pointed out we have a rather long life span…it IS having an effect on shorter lived and fast breeding species like the various bacteria though.
I would have to say that, even in a few thousands (10’s of thousand? Hundreds of thousands?) IF it has an over all effect that its not going to spell gloom and doom for the species. Even if we, for some odd reason, go back living in caves and forget all about this new fangled technology stuff, there should still be sufficient genetic diversity to ensure we have broad hipped women to bear our smaller children (due to lower nutrition from living in caves) and continue the species. I’d have to say that women with the ‘narrow hipped gene’ are probably not going to do well in such primitive conditions…but that, as a species, this would be the least of our worries. The population in such a case would plummet from billions to maybe a few million world wide…and the cause isn’t going to predominently be due to women dieing in child birth (IIRC during such primitive times, even without this ‘narrow hipped gene’ being widely in the pool, women had something like a 30-50% death rate in child birth…pretty frigging grim), but initially mass starvation, followed by going back to dieing of acute type diseases and not having to worry about all the chronic ones that get us later in life today.
Of course, if we keep our technology thousands of years from now it won’t be much of a problem…
Good point. My wife had a C-Section with our first child because she went undiagnosed with gestational diabetes and our son was huge…no way she could have a natural birth. Without modern medicine both my wife and son would have died.
This sounds too high. In seventeenth-century London, women had perhaps a 20% chance of dying in childbirth over the course of a lifetime, and that was under about the worst sanitary conditions imaginable (death rates outside of the city were far, far lower, and I suspect they would have been for cave women as well – the sheer density of the population was the problem, complicated by the fact that medical intervention often made things worse rather than better by spreading infections).
