A potential major advance has been claimed by scientists who say they have created "synthetic" human embryos without the need for eggs or sperm. But it has come in for criticism.
The work of Prof Magdalena Zernicka-Goetz, of the University of Cambridge and the California Institute of Technology, was announced at the International Society for Stem Cell Research's annual meeting in Boston on Wednesday.
According to a report in the Guardian, she told the meeting: "We can create human embryo-like models by the reprogramming of (embryonic stem) cells.”
It is unclear whether the model embryos have the potential to continue beyond the earliest stages. But advocates claim the work may help study illnesses, genetic disorders or recurrent miscarriages.
Professor David Albert Jones is director of the Anscombe Bioethics Centre, an Oxford-based research institute serving the Catholic Church. He says that aside from the ethics, it is questionable if the news is an "advancement in science".
“We already have experiments on human embryos; we already have cloning of human embryos; we already have a mixing of human and non-human embryos. This is an answer to a whole area, which we should be very critical about”, he told Premier Christian News.
“And we should also remember each time this comes up, very grandiose claims are made about how this will cure all diseases, and we're going to cure Alzheimer's. But then it never happens," he continued.
“All that happens is they then might have another proposal to do more kinds of experiments, to get more kind of understanding, but we never actually get to the medicines," he said.
Commentators like Professor Albert Jones point out that the research falls outside current UK legislation and raises ethical and legal issues.
“Depending on where the work was done, it's not clear to me which regulator it comes under and whether it would come under the Human Embryology Authority," he told Premier.
“If it did come under the English regulator, I am mildly surprised that it has been allowed because they cultivated it past 14 days. And that's one of the rules that you're not supposed to," he said.
Professor Robin Lovell-Badge, head of the stem cell biology and developmental genetics laboratory at the Francis Crick Institute, told BBC Radio 4's Today programme on Thursday that the research aimed to model early human development.
"So these structures that have been made so far are clearly not perfect models of human development because they don't go that far.
"However, the whole intention is to devise ways of making them more and more perfect models.
"And of course, then the closer you get to a human embryo, then you have to start (thinking) 'well, what's the difference between a normal human embryo and one of these models?'"
Professor Albert Jones agreed.
“It's experimenting on human embryos if they are human embryos. I mean, as I say, it's not; it doesn't work very well at the moment”, he reflected.
“So they're trying to make it better. And the better they get at it, the more embryo-like it looks, and the more likely it is that they are actually destroying human embryos, the less like an embryo looks, the more they're just messing around with stem cells," he explained.
“But then why are they doing it? If they're not doing it very well. So the better they get scientifically, the more problematic it is ethically," he concluded.