Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Caesarean births 'affecting human evolution'

bbc.com

Post reply on HN
Print view View original

61–66 of 66 posts

Re: Caesarean births 'affecting human evolution'

#61

Post by undersuit »

y04nn wrote: post #52
bambax wrote: post #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 ha…

I also have a lots of doubt about this study, the article says '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.' 1960 -> 2016 = 56 years, can natural evolution show signs so fast? Also 'cases where the baby cannot fit down the birth canal' is a subjective, standards may have evolved, maybe babies are also bigger?

>maybe babies are also bigger?

Well adults are bigger. Average height has been increasing worldwide and better nutrition is the accepted cause. So maybe(most definitely) a pregnant well-fed mother will produce a larger baby than a mother eating more like those in generations past. We've been evolving for safe delivery of babies while teetering on starvation, not when so well fed that 25% of the US population is obese.

Re: Caesarean births 'affecting human evolution'

#62

Post by sjg007 »

nugget wrote: post #54
pg314 wrote: post #36

Earlier quoted context omitted.

That already happens sometimes: it's called IVF with PGD (pre-implantation genetic diagnosis). Before an embryo is implanted a cell is taken from it and tested for genetic defects. It's an expensive and convoluted process, so it's only done when one or both of the parents are carriers of a serious genetic mutation.

> it's only done when one or both of the parents are carriers of a serious genetic mutation I have friends who have done PGD simply to select the gender of their child. Once researchers identify reliable genetic markers for height and intelligence, expect PGD to become rapidly more popular among the upper class.

Well you can just pick a spouse who is tall and smart?

Re: Caesarean births 'affecting human evolution'

#63

Post by dragonwriter »

y04nn wrote: post #52
bambax wrote: post #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 ha…

I also have a lots of doubt about this study, the article says '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.' 1960 -> 2016 = 56 years, can natural evolution show signs so fast? Also 'cases where the baby cannot fit down the birth canal' is a subjective, standards may have evolved, maybe babies are also bigger?

> can natural evolution show signs so fast?

Yes, in fact, I think the accepted dominant manifestation of natural evolution is rapid change in trait distribution in response to significant change in enviromental pressure, and near stasis otherwise, not continuous slow change.

Changing a trait from near certain death of mother and child to one which, while it has some increased risk, is normally survivable without lasting adverse consequences for either mother or child is an enormous change in terms of the degree of selective pressure against the trait.

That's not to say there aren't other potential contributors, but it's not unreasonable for natural evolution to have measurable effects in the timeframe in question in those circumstances.

> maybe babies are also bigger?

The article expressly calls that out as a contributing evolutionary trend that was itself limited by the fact that beyond a certain point, that becomes fatal. So, that's certainly true, but in no way a contradiction to the point in the article.

Re: Caesarean births 'affecting human evolution'

#65

Post by Chris2048 »

UweSchmidt wrote: post #23

Do we really need caveman-capabilities? To be ready for the day we lose our tech and have to start over? In a different context it has been discussed how we have used up our easily accessible energy and may not be able to restart civilization on this planet. So why keep lowtech genes around? Make way for large brains and large heads!

State/government-dependence to give birth is a worry!

Re: Caesarean births 'affecting human evolution'

#66

Post by antisthenes »

sjg007 wrote: post #62
nugget wrote: post #54

Earlier quoted context omitted.

> it's only done when one or both of the parents are carriers of a serious genetic mutation I have friends who have done PGD simply to select the gender of their child. Once researchers identify reliable genetic markers for height and intelligence, expect PGD to become rapidly more popular among the upper class.

Well you can just pick a spouse who is tall and smart?

Then how do you deal with people who did not get a tall and smart spouse?
Post reply on HN