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Comment by Teever | Hacker News Reader

> Lastly, the stem cells we're planning to use to make these eggs accrue mutations with age, and we don't currently have a good method to fix these before making them into eggs. These mutations will bring additional risk of various serious diseases, only some of which we currently have the genetic screening to detect.

I've always found this one fascinating. Somehow human cells age and humans get old and die but humans can somehow make an entirely new creature through reproduction where that is reset and most of the defects from the parent are gone as well.

How does that work and what stumbling blocks exist that prevent us from replicating it?

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> Somehow human cells age and humans get old and die but humans can somehow make an entirely new creature through reproduction where that is reset

I think the eggs aren't dividing as you age (you are born with them, so to speak) and the sperm is held "outside" the body.

One is in original packaging and the other is produced in a "cooler" enviroment by the billions with a heavy QA failure of 99.9999%.

I don't know anything about this subject, but I thought it was just natural selection that effectively filtered out the 'bad eggs', as it were. On that same note, I've worried about the effects that modern medicine might have in short-circuiting evolution/natural selection. Would love to hear from someone with qualifications to speak on this matter.

Modern medicine absolutely short-circuits natural selection. If you have an older sibling who was delivered via C-section chances are you wouldn't exist.

That’s not true for the USA however.

The large award for a medical malpractice trial was the reason for doctors pushing for a C-section if there’s any possibility of a complication. (Sometimes called defensive medicine.)

Most people point to the cases won by John Edwards, trial lawyer and vice presidential candidate as the reason for the great increase in C-sections. His case wins include 30 trials at which he won at least $1 million dollars each.

In my generation (80s-90s) pretty much everyone in Brazil that was born in a hospital was born through C-section. Only recently did the practice of defaulting to c-section is beginning to fade.

Modern medicine is part and parcel of natural evolution. There is no short-circuiting of evolution. That's not a thing.

There are a bunch of mechanisms in sperm/eggs for better protection/repair/removal by suicide than in any other tissue. It makes sense that these evolved to be the best in these cells compared to any other. Also other tissues might have significantly worse problems having cells kill themselves instead of continuing to operate with a corrupted genome.

We’re were photocopying photocopies. But I guess if you’re taking two copies and tracing a third that is based on them but doesn’t actually have to be a facsimile, it gives nature more flexibility?

Like I’m not sure it actually works this way but I can intuit why it’s possible, given the new life doesn’t have to be an exact replication.

It's not quite reset. Harmful mutations do accumulate. Sexual reproduction is how we keep up with them - the selection effect (probably most of it at the sperm stage?) pushes it so that you're more likely to get a child with the less-damaged sides of their parents's DNA.

Isn’t that what stem cell therapy is?

Naturally the reset happens before most cells have grown, part of the trick in doing it with grown humans is doing so without destroying existing tissue or causing cancer.

It's almost like trying to change the flavor of a cake after it's been baked. Significantly easier to swap out ingredients before it's that far in the process.

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