Cesarean Births Could Be Affecting Human Evolution, Study Says (bbc.com)

CanadianRealist writes: Larger babies delivered by cesarean section may be affecting human evolution. 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, [according to estimates from researchers at the University of Vienna in Austria.] Science Alert reports: "In the past, larger babies and mothers with narrow pelvis sizes might both have died in labour. Thanks to C-sections, that's now a lot less likely, but it also means that those 'at risk' genes from mothers with narrow pelvises are being carried into future generations. More detailed studies would be required to actually confirm the link between C-sections and evolution, as all we have now is a hypothesis based on the birth data." Agreed, more studies required part. Cesareans may simply be becoming more common with "too large" defined as cesarean seems like a better idea. It's reasonable to pose the question based simply on an understanding of evolution. Like it's reasonable to conjecture that length of human pregnancy is a compromise between further development in utero, and chance of mother and baby surviving the delivery.

Comments

More likely medical practice, not evolution

[Kjella]

Well 0.36/0.30 = 20% growth and it's only been ~2 generations, if you consider that most of the 3% in one generation will have kids with the other 97% in the next generation it seems unlikely to happen this fast. It's probable that it's more routine and we're more cautious today, so borderline cases get the surgery now where they wouldn't in the past.

Re: More likely medical practice, not evolution

[Anonymous Coward]

Ah no. Sorry. Cuba in fact has more doctors. Cuba is a doctor factory - they literally export them all over the world. Greece is up there, but lags behind several countries.

Re:More likely medical practice, not evolution

[CanadianRealist]

I submitted the article. I completely agree with what you say. I did mention the idea that the definition of babies being "too large" might be changing due to cesarean becoming more routine. And I agree this seems to be happening too fast.

What I considered really interesting was the question: if cesarean became the normal method of delivery for an extended period of time (many generations) could humans end up at a point where natural birth was not possible?

Alternate explanations

[Anonymous Coward]

Are there alternate explanations that also fit the trend? Many mothers are more careful about their health habits during pregnancy now than in the past, in large part due to a better understanding of what is helpful and harmful to the unborn child. Access to better prenatal care also certainly has improved the health of unborn children. Unhealthy babies often are smaller than healthy babies, and if there are fewer unhealthy babies now, then it follows that the average weight would increase. Although not healthy, there has also been a trend toward higher obesity rates, especially in some developed countries. Obese mothers sometimes give birth to very overweight babies, which is unhealthy for the child. An upward trend in obesity should lead to an upward trend in heavy babies, all else equal. It seems like these hypotheses could also explain the observed trends.

There's an obvious alternative explanation

[bigHairyDog]

Babies have been getting bigger for a long time.

This is well documented in medical literature:

- "These findings suggest that US and Canadian babies are getting bigger" https://www.ncbi.nlm.nih.gov/p...
- "We conclude that Canadian infants are getting bigger" https://www.ncbi.nlm.nih.gov/p...
- "Results presented in this study demonstrate that even when migratory effects are eliminated, a secular increase in birth weight is observed" https://www.ncbi.nlm.nih.gov/p...

Re:There's an obvious alternative explanation

[Anonymous Coward]

Why? Are you scared of becoming a big baby?

Re:There's an obvious alternative explanation

[Bongo]

Lierre Keith makes a good point, that returning to natural grazing cows would be a huge benefit for the environment. Yes, I'm a methane fart denier. But her concern is with biodiversity, and all that tofu and grain is coming from stripping the land back to monocultures. I'm all for eating meat grown in a lab, if needed, but as humans, we have small digestive systems and big brains, and we didn't evolve that way eating veggies. But that's evolution for you, a lot of trial and error. Like this with the babies. Apparently there's a case that if the baby comes out "clean" via cesarian, its biome won't get booted up properly and it'll end up with various conditions later in life. So ya have to smear the face with mommy juices and poop. Because nature is just not interested in whether something looks disgusting, nor whether it is a competition between hunter and prey, nature just works how it works. That's my thought for the day, methinks.

Re:There's an obvious alternative explanation

[execthis]

The first hominid ancestors to us whose brains quickly developed much larger were avid seafood eaters. There are a number of telltale biological clues to this in our physiology, including the fact that our bodies don't manufacture DHA yet our brains and nervous systems require high levels of it. Also DHA is passed through the placenta to the fetus implying that the ancestors had an abundant supply of it in their diet.

Re:There's an obvious alternative explanation

[serviscope_minor]

The first hominid ancestors to us whose brains quickly developed much larger were avid seafood eaters.

They were also avid fruit eaters (we can't make vitamin C) and avid starchy vegetable eaters (unlike our closest relatives, we can digest starch).

Re:There's an obvious alternative explanation

[Anonymous Coward]

Q: What's the easiest way to tell if someone is a vegan?

A: Just wait, they'll tell you.

Re:There's an obvious alternative explanation

[Comrade Ogilvy]

Probably some combination of both.

If you can withstand often breathless and hyperbolic writing, I do recommend the book Born to Run, that discusses the idea that homo sapiens, in particular, are the supreme runners at long distance at moderate speeds, for the purposes of running down prey to death, which is a very effective hunting method in hot & dry climates when you have not developed good hunting weapons yet. I believe the conclusions are largely correct.

However, there is another tale that suggests hominids were semi-aquatic, due to periods of time in east African where swaths of grazing/hunting grounds were periodically flooded. The evidence is circumstantial, but intriguing IMO. Opportunity: the historical fact of the flooded areas. Bipedal movement: which is easier to transition towards from chimp/ape walking styles in water where buoyancy helps you along until your descendants legs evolve towards that style of movement, plus it is obvious very useful to keep you head and children out of the water. Our nose: because a large downturned nose of our style is a rarity, but makes sense for keeping water out of the air tracts if you are dog paddling through shallow water. (Remember: that bipedalism sucks for swimming, unless you are a very skilled swimmer; in comparison, virtually all quadrupeds can be dropped into water and make their way around and not drown.) Hairless bodies and thick subcutaneous fat layer: this is a common pattern for aquatic animals. Flat feet: good for walking in mud.

Of course, this is not either/or. Both tales could easily be true. Hairless and subcutaneous fat makes sense in both scenarios.

Its everywhere

[Anonymous Coward]

Cesarean Births, Insulin and condoms may be affecting evolution...news at 11.

Re:What about infertility?

[Hognoxious]

Yes. A study done at the University of Dublin concluded that if your parents didn't have any children you probably won't either.

Is age a factor?

[geekmux]

Previous generations and marriages gave birth to a more traditional (old-fashioned?) household, where the father was the only provider, and the mother stayed home to raise children, starting at a young age (late teens/early 20s). Compare and contrast this to what we see today as more of the average, where both adults perhaps go to school, start careers, spend time traveling the world, and then start considering marriage and a family in their late 20's/early 30's.

And this is not meant to sound mean or degrading, but we humans don't exactly shrink in size as we get older, thus making pregnancy and childbirth that much harder on a human body that may be leaning more towards the overweight or obese range. Perhaps mentally, the ideal age to become a parent is mid-30s due to maturity/wisdom/financial status/etc, but from a purely physical standpoint, childbirth is likely ideal at a much younger age, which a younger body may provide a bit more flexibility when it comes to childbirth.

Re:Is age a factor?

[Rande]

I've heard quite a few women look down on mothers who chose to have children at 18 or 19 - either for being considered feckless scroungers bleeding the social system dry or for not being feminist enough and having a full career first.

I think 18 is a very good age to have children. Straight after high school and it's not too late to go on to college at around 22ish. Admittedly you'd need a lot of family support, which is a good thing no matter what your age.

Re:Is age a factor?

[mvdwege]

Yes, because the incidence of that happening is almost insignificant, and using it to stigmatise all young mothers is simply wrong.

Re:Pratchett and Baxter already predicted this

[Joce640k]

It's actually a thing, Google "elective cesarean birth".

Women want to plan their expensive baby-party for a particular day, etc. You can't leave that to chance, not when you need to book the venue and the catering.

A lot of women also don't want to go through all that scary 'labor'' business or get their prize-winning vagina all stretched out.

Re:Pratchett and Baxter already predicted this

[LiSrt]

A lot of women also don't want to go through all that scary 'labor'' business

Who would?

Re:What about infertility?

[jabuzz]

Sorry but that is currently impossible to test because their are insufficient babies born from IVF that have actually reached adulthood to really analyse that.

I would note that Louise Brown has had two children conceived naturally and her sister Natalie has had four children all conceived naturally. For those ignorant of the facts Louise Brown was the first IVF child in the world and her sister was the fortieth born four years later.

Note that shows the low levels of IVF babies being born in the early years of the technology and why there are too few IVF born adults to really conduct any study into their fertility.

Re:ummmm ....

[Anonymous Coward]

There has only been one documented, (Poorly...), instance in History that Humanity physicality changed in a relatively short period of time- the 14th century. Starting in China, maybe, it spread throughout India, and then the Caucasus, into the Middle East and then north deep into the Scandinavian Countries. In two or three generations, half of the population of Europe died off due just to the Black Deaths. We don't know much about the other Civilizations.
One curious outcome can be seen in the clothing of the period. Europeans somehow got significantly taller over the following Century, after being stuck at Roman heights for over a thousand years. (Check out Suits Of Armor for a striking example.) Whether due to better nutrition; famines were common before the Plagues due to overpopulation and poor Farming practices, or whether there was some recessive Genetics going on due to past uncounted and unrecorded Plagues, is not now known. It's probably both; certainly poor nutrition can stunt inherited growth tendencies. And note that even without the Plagues, Infant Mortality bounced around 50%... Also note that this time was also the start of the "Little Ice Age", so Environment can't be ignored.
The European Countries in general, and the US in particular, have plateaued; 18 year old Males whose statistics have been gathered for centuries by those who like to play with War, have been tending to an average height of ~70 inches. In 1914, the average height of the Fresh Crop was ~67 inches.
But the growth in height is startling in some newly developing countries. In South Korea, it is now ~69 inches for Males. But in 1914, it was ~63 inches. Six inches is a pretty good jump, but South Korean women have jumped further- A gain of ~8 inches.

People have been growing bigger, but not at the same rates or at the same time. Generally, skeletal dimensions scale; taller women have wider pelvises. (Some populations in hellholes are actually getting shorter.):
http://www.npr.org/sections/goatsandsoda/2016/07/27/487391773/americans-are-shrinking-while-chinese-and-koreans-sprout-up

Cesarean births are still rare, and to draw any conclusion about general Evolution from their _recent_ trends is foolish. This is a damn stupid study; I suspect that there is an Agenda at work here. BTW, over the last few decades, the average US or Canadian baby has gotten slightly smaller:
http://www.wsj.com/articles/SB10001424052748704423204575017471267586344

Re:Pratchett and Baxter already predicted this

[MightyYar]

You just came here to brag that you've sampled a statistically significant number of women.

dogs did this

[deadweight]

Some breeds of dogs, bulldogs maybe?, HAVE to be born via C-section. The puppies can no longer fit the natural way.

Re:dogs did this

[Oswald McWeany]

Some breeds of dogs, bulldogs maybe?, HAVE to be born via C-section. The puppies can no longer fit the natural way.

And now some women have to have children born via C-Section. I think this is proof that bestiality is on the rise.

Re:Pratchett and Baxter already predicted this

[Anonymous Coward]

You seem to suggest that it's not all that scary, not all that painful and not all that stressful. I encourage you to put a grapefruit up your ass and squeeze it out - and it still wouldn't be nowhere near the pain women feels during labor. Have you ever had a cramp? How long did it last? Try to prolong it for 6 hours every 5-10 minutes.

And why it's a bad thing women try to prevent their vaginas from being stretched out? Imagine that each time your partner gets pregnant someone cuts off one or two inches of your dick. Would you try to prevent that?

Doctors and patients are more risk (& pain) av

[Bearhouse]

Medical liability cases are increasing around the world, and the cost of insurance is driving many people from the profession. (See articles)
My wife wanted to give birth at home, it was both very difficult to organise and extremely costly.
All her friends said she was mad; plan the date with your Dr. for a C-section, fast, painless and no stress waiting for contractions to start.
It's as much a matter of convenience for both sides as a question of baby size IMHO.

http://www.medscape.com/viewar...

http://www.spiegel.de/internat...

Re:This is why we need Trump

[dcw3]

TRUMP 2016!!!

I don't think this is what he meant by "grab them by the pussy"

De-evolution

[markdavis]

We have been de-evolving for a long time now. Lots and lots of "defective" people are living to reproduce who would have died without medical science (I am one of them). This ends up making the species genetically more poor each time.

Re:De-evolution

[Anonymous Coward]

Properly speaking, there is no such thing as de-evolution. Evolutionary pressure optimizes for survival in some particular environment, and nothing more. In this case, the particular environment is changing to one that includes medical science, so certain types of genetic specialization is no longer needed. People don't de-evolve more than bacteria de-evolve when they lose antibiotic resistance due to a lack of antibiotics :)

Re:Pratchett and Baxter already predicted this

[dcw3]

Who would want to go through surgery if they didn't have to, and then go through a year long period of recovery?

Apparently, at least 3%...that's just the number that were granted, not the number who requested it.
http://www.cosmopolitan.com/he...

Re:Pratchett and Baxter already predicted this

[dcw3]

I'll just say that in my anecdotal case, where the doctor showed me the view up there, and I thought I'd never fit in that thing again...It all snapped back. Those things are AMAZING!

Everything affects evolution

[fluffernutter]

Anything that affects mate selection affects evolution... Mundane things such as wearing makup and shaving body hair are probably affecting evolution.

Flawed conclusions

[JoePete]

This study appears to have multiple flaws: 1) A statistical increase in Caesareans does not mean a statistical narrowing of the pelvis. There is not a causal relationship. This is like suggesting that because relatively fewer people are having their wisdom teeth extracted today, our mouths must be getting bigger. 2) Even with a correlation between pelvis width and Caesareans, it does not mean those children or mothers would have died in non-surgical child birth. This is creating a binary relationship out of a correlation - or in other terms assuming the absence of a negative is a positive. Other factors: - The general guideline today (as I understand it) is that if you have had a Caesarean in the past it is safer to have Caesareans for future babies - this alone might account for the statistical increase. - Larger babies can be attributed to better prenatal health and nutrition. - The increase in Caesareans can be attributed to more women giving birth in a hospital setting where Caesarean is an available and safe option.

click bait

[AndyKron]

There's no evidence. This is click-bait bullshit.

Re: Pratchett and Baxter already predicted this

[Hognoxious]

Caesars carry risks

I agree. Unwashed lettuce can give you worms, and raw eggs can carry salmonella.

Re: This is why we need Trump

[bev_tech_rob]

I hope Trump gets rid of vaccinations while he's in office. These diseases are here to help rid our gene pool of bad genes, yet we keep trying to save those less fit. It only hurts our species in the long run!

We need NATURAL selection.

Jenny McCarthy is right -- even if for the wrong reasons.

Good deal. At the next Ebola outbreak, hop on a jet over to that location and help bury the bodies, but you can't wear any protective gear. If you have 'superior' genes, you should be fine, right?

Jerkwad...

Re: Pratchett and Baxter already predicted this

[Oswald McWeany]

Caesars carry risks.

Especially if you're a Gaul, or believe in Rome remaining a republic.

Re:This is why we need Trump

[KiloByte]

TRUMP 2016!!!

I don't think this is what he meant by "grab them by the pussy"

Not that I'm supporting Trump (he's more evil than Cthulhu, almost as bad as Hillary), but have you noticed how those 30ish women who accused him of sexual assault all went silent the moment the election was over? Shouldn't they be trying to bring him to justice? Maybe, just maybe, it was all staged false accusations as certain people like this kind of methods? See Assange, or what esr was tipped about.

Re:What about infertility?

[Oswald McWeany]

The answer is yes. A lot of negative genes that would have resulted in a person not reaching reproductive age are being propagated whereas they might have died out if we were less advanced. Negative mutations in our genomes are not being removed like they once were.

It is theoretically possible that 200,000 years from now, humans would be completely genetically unviable without technology. (although technology will probably remove the bad mutations long before then in the real world).

Part of what the Nazi's were doing when they executed handicapped people was trying to maintain the purity of the genes and keep the "race strong" removing genetic impurities. Nasty stuff. Obviously a route we don't want to take, one can assume they wouldn't have been too happy about the number of Caesarians these days.

Re: Pratchett and Baxter already predicted this

[mwvdlee]

Unless you're from this particular village in Gaul, in which case Caesars offer barely any risk.

Re:Not evolution

[Oswald McWeany]

Evolution is not linear and does not mean "improving". Evolution merely means a general change in gene frequencies over time. In terms of biology there is no such thing as "devolution". The increase in frequency of a trait that one might perceive as "negative" is still "evolution".

Re:Pratchett and Baxter already predicted this

[Joce640k]

I'm curious about the vagina stretching.

Rule 34...

Re:Pratchett and Baxter already predicted this

[cayenne8]

It's not about keeping it tight for their partners...

Err...I beg to differ.

I mean, most guys grow weary REALLY quickly of loose pussy and saggy tits.

Those two things are a big reason they divorce and 'upgrade' to a newer model after a few years.

Re:What about infertility?

[cayenne8]

A lot of negative genes that would have resulted in a person not reaching reproductive age are being propagated whereas they might have died out if we were less advanced.

I guess that explains the dramatic rise in the number of plain old fucking stupid people I've started encountering as my life goes on.

Seriously, there really seems to be MANY more of them around these days.

Re:Pratchett and Baxter already predicted this

[PIBM]

My wife says that childbirth (4 kids, so it`s a relatively good sample) is nothing compared to either kidney stones or appendicitis. There, stop propagating that myth, it`s not that bad.

Re:Why are larger humans a good thing?

[Jzanu]

Yes, physical size allows for larger cranial volume which is directly linked to intelligence across all primates. Prenatal development to greater physical size allows more neurons to form early - we may see trillions instead of billions of neurons forming eventually. This directly allows for greater intelligence later.

Am I the only one?

[Jfetjunky]

Am I the only one who immediately thought about all the breeds of dogs humans have essentially bred to suffer because they were artifically selected to have such smooshed, huge faces they can barely breath, and also can't even deliver their own puppies without a C-section?

Re: This is why we need Trump

[penandpaper]

Trump was in the white house a few weeks ago and he did shake Obama's hand. Coincidence? I think not.

Re:Why are larger humans a good thing?

[Jzanu]

Read. I'm not here to lecture to you. It's basic knowlede in evolutionary anthropology and anatomy.