[jtbayly]

>"For one thing human embryos would have already been implanted in a womb for a week at that point"

At what point? Implantation typically occurs 6-12 days after fertilization. This experiment starts at the equivalent of day 7. IVF is a thing.

It sounds like you're just guessing.

Edited to add, this article says "It would be illegal to implant them into a patient’s womb" which is a far cry from what you are implying, that it would be impossible.

https://www.theguardian.com/science/2023/jun/14/synthetic-hu...

[Retric]

I thought I was repeating what the article said:

“This stage corresponds to day 7 of the natural human embryo, around the time it implants itself in the womb.”

“The researchers discovered that if the embryo is not enveloped by placenta-forming cells in the right manner at day 3 of the protocol (corresponding to day 10 in natural embryonic development), its internal structures, such as the yolk sac, fail to properly develop.”

“The stem cell–based embryo-like structures (termed SEMs) developed normally outside the womb for 8 days, reaching a developmental stage equivalent to day 14 in human embryonic development.” (So ~1 week post implantation for a human embryo.)

[jtbayly]

None of your quotes indicate that it would be impossible to implant these. The article is beating around the bush, but essentially it is saying "These could potentially be implanted." That's why people are somewhat up in arms about this. Read the other article I linked.

This research in animals has led to successful implantation, but not live births. Nobody knows why yet.

[Retric]

Nothing I said had anything to do with if these were viable or could be made viable, just that they aren’t direct equivalents.

People could be up in arms if hypothetically 50% of these where viable, but the nonviable 50% would still cause errors when compared to human embryos. Alternatively, 100% could be viable and they could still be different in critical ways from natural human embryos resulting in universally late or premature births etc. Or perhaps 0% are viable and people just don’t understand the nuances.

It’s therefore an orthogonal question.

[jtbayly]

You don’t appear to be able to say anything helpful about what “model” means in this discussion. The only explicit claim you made (that they were different because they would have been implanted in a womb for a week already) was incorrect. Some would likely have been implanted for a day.

[Retric]

Your timeline is off, the egg can take nearly 2 weeks to implant but that requires a delay in fertilization. This 14 day timeline is specifically in reference to fertilization not the release of the egg.

The discrepancy exists because people can track the day of ovulation and hormonal changes from implantation but actual fertilization has no obvious signs, unless your doing IVF or something and looking at the actual egg.

That said, extreme outliers may exist but that’s not what we’re talking about.

[jtbayly]

IVF is exactly how one would implant these embryo "models," and that's why I brought it up in my first comment.

Here's an example of how IVF embryos are graded at day 6, prior to implantation:

https://flo.health/getting-pregnant/trouble-conceiving/ferti...

I think you missed the fact that these models start at the equivalent of day 7, so we're right in the same time window of implantation. Unless you are claiming that exactly at 6 days after fertilization is when every single embryo implants, and at 7 days it is simply too late. But your whole point seems to be that the window is hard to observe, so I doubt that's what you mean.

At any rate, I still see nothing to indicate that these "models" are not simply embryos. I think they are intentionally calling them models so that they can skirt the legal requirements about embryo research.

Unless of course you can point me to something that is actually different about one of these models vs an embryo. The whole article is about how they are the same.