An experiment reported on Thursday in Cell, a peer-reviewed scientific journal, announced a purported breakthrough in bioengineering: the successful creation of an embryo with both human and pig DNA (and to be clear, the artwork above is just a photo of a sculpture). The results, "raise the possibility of xeno-generating transplantable human tissues and organs towards addressing the worldwide shortage of organ donors," according to the paper. But while the embryo was only allowed to develop for a few days, the genesis of this early-stage creature revives an uncomfortable debate about whether animal-human hybrids are, well, horrifying monsters waiting to happen.

In November 2015, shortly after the National Institutes of Health (NIH) put a hold on its own experiments that combined human and animal cells, the federal government hosted a meeting of the minds to discuss that very question. More specifically, the NIH feared "the specter of an intelligent mouse stuck in a laboratory somewhere screaming 'I want to get out," NIH ethicist David Resnik, told Technology Review magazine.

NIH may have been acting out of an abundance of caution, but there are still potentially icky dilemmas to work out. We still don't know how these early-stage bundles of fetal cells translate into human parts on or inside a pig. Some areas for human cells, like the stomach, are less troubling than if they materialized in, say, the brain. To find out we're on the verge of a horror movie scenario, I talked to medical ethicist Arthur Caplan of New York University's Langone Medical Center. He told me more oversight for scientists like Wu might be a good idea, but not for the reason I thought he would. He also said we're kinda-sorta, already animal-human hybrids.

VICE: What concerns have ethicists raised when they saw the human-pig hybrid embryo?

Arthur Caplan: People go, "Well, is this adequately regulated? Did they have enough approval or oversight to do the experiment?"

Did they?

I think they did, but that's certainly a debating point: whether there ought to be [more governing bodies] examining what's going on in a more transparent way.

"People aren't expecting it and all of a sudden they hear someone say 'Now they're making animal-human people.'" — Arthur Caplan

What would those groups be looking for?

They wouldn't be looking for much different. They would just be making it known to the public that these experiments were coming. They have much more of a shock value. This reminds me of when Dolly the sheep was cloned. It just got kind of announced in the newspaper. And people were like, "What the hell? Who did that? Why'd they do that? What's going on?" This has some elements of that: shock value because people aren't expecting it and all of a sudden they hear someone say, "Now they're making animal-human people."

OK, so was this tantamount to making animal-human people?

No. Certainly there's a risk that something could go haywire, and cells going where you don't want them, like the brain, or some other place. But that's a pretty low-risk phenomenon. It's a risk, but it's low-risk. And you could certainly stop the development of the animal if you had any reason to think that was occurring.

The brain cells would still be physically inside a pig, so...

And with a pig's nervous system, so I don't know! It's hard to know what the hell that would be. It certainly wouldn't be human. It wouldn't be like there was a homunculus inside the pig. [And] having some cells that are partly human in the brain undoubtedly isn't going to be a fully formed brain.

If that's not the worry, then what is?

I think what we don't want to happen is making cross-species people. We all agree on that. That's the good news. I don't think anybody's particularly interested in making minotaurs, or griffins, or other types of cross-species animal. There's just a shortage or organs and tissues and things for transplant. So I think the motivation is good, and I think the scientists who did the work are very competent.

Well, someone might have an interest in making griffins...

More to the point, there's not much money in that. If you want to make money, make something you can transplant. If you want to make headlines, run around saying you're going to make animal-human chimeras.

Won't there be new dilemmas at the phase where we're harvesting what are supposed to be human organs, but getting them from a pig, and possibly making ourselves into animal-human hybrids?

Yes, that would be much more dramatic and interesting and would raise more boundary questions than the current experiment. [But also], there are a lot of objections coming up about having cells from humans inside animals, but most of us have this experience every day when we have breakfast: animal cells coming into our bodies, and getting incorporated into us—becoming us—in the form of bacon or whatever.

You're saying eating meat makes us pseudo-hybrids already?

When you eat meat—or for that matter, cauliflower—it's transforming into you. [Or] to put it another way, when you eat bacon, it's pretty far removed from the animal it came from, but then you pull the bacon off the pig, cook it, and eat it, people get the sense that they don't engage with animals in a critical way every day.

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