A new relationship with animals, nature and each other.

Pigs with Human Brains


Imagine a pig with a human brain. It could happen. Researchers at UC Davis, California, are trying to grow human organs in pig embryos so they can be transplanted back into human patients.

But if any of the human stem cells they inject into these embryos start migrating around the body, the baby pig might start growing a human brain, too.

Welcome to the brave new world of gene editing. Here’s how it works for human patients needing a new heart, liver, pancreas or whatever:

The doctors start with a baby pig embryo, and “edit out” or delete the DNA of its corresponding organ. (The pancreas is the one they’re currently experimenting on.) Then they take some of the patient’s stem cells and inject them into the embryo. Since the nature of stem cells is that they can develop into almost any other kind of cell, the idea is for the human stem cells that have been injected into the pig embryo to fill the space of the DNA that’s been removed and to start growing a real organ there.

This embryonic organ is essentially a clone of the one that needs replacing in the patient, just younger and healthier and one that the patient’s immune system won’t reject since it won’t recognize it as a foreign body.

Things get very complicated when you have a conscious human being living in a pig body.The catch (well, one of the many possible catches!) is that when those human stem cells are injected into the pig embryo, they might not only fill the “empty” space where the pancreas should be; they might start migrating around the embryo and take up residence in other places – like the brain.

And so, when the fetus is born, you’d have a pig with a human or part-human brain. And therefore human consciousness. All in all, the stuff of a sci-fi nightmare.

Two different nightmares, in fact. Bearing in mind that the brains of pigs and humans are already very similar, the issue from the pig’s point of view isn’t that she suddenly becomes conscious. Pigs are already conscious; it’s that with the added human awareness of what’s happening to her she becomes more vulnerable to suffering.

From the human point of view, however, the welfare of the pig is a minor consideration. (If it were otherwise, laboratories and factory farms would have been shut down long ago.) No, our concerns are a) the thought of a human being trapped in a pig’s body; and b) that a pig with human consciousness muddies our need to believe that we are fundamentally different from the other animals.

In other words it’s not really about the pig; as usual, it’s all about us.

The researchers, meanwhile, are hurrying to assure us that any likelihood of any such thing happening is very small. “We think there is very low potential for a human brain to grow,” lead researcher Dr. Pablo Ross says on the BBC news program Panorama. “But this is something we will be investigating.”

Stem cell expert Robin Lovel-Badge, of London’s Francis Crick Institute, disagrees, telling Panorama that researchers simply don’t know what these human cells might do. In particular, he says “we are worried about the brain.”

The National Institutes of Health (NIH), the main agency for medical research in the U.S., is equally uncertain, and has declined to provide funds for this research as long as there is any doubt. (Not that that’s a problem to Dr. Ross; he has private funding.)


There are, of course, thousands of experiments going on all the time involving laboratory animals with human DNA. But when they start growing human brains, things get complicated because we now have a conscious human being living in a pig body.

For Dr. Jeffrey Kahn of the Johns Hopkins Berman Institute of Bioethics the question arises: what is the nature of a human being:

Few would argue that a pig with a human pancreas is still just a pig. But what if it has a human pancreas, a human kidney, a human liver, and a human heart? The question’s going to arise eventually: When does it become a human in a pig’s body?

Bioethicist Professor John Harris explains the NIH’s concerns:

They fear that the presence of human cells in the modified animals might “humanize” the animals’ brains to the extent that they possessed human sensibilities, cognition, and rationality. Such capabilities would not just merit moral and legal protections comparable with creatures like ourselves- they would demand them. In short such animals, becoming more human, would have rights analogous to human rights.

This, of course, would change our entire conception of our place in the animal kingdom – our entire relationship with the natural world.

I posed the question to attorney Steven M. Wise, founder of the Nonhuman Rights Project, which has been making news around the world with its lawsuits on behalf of captive chimpanzees. In court, Professor Wise makes the case that certain animals are cognitively and socially complex beings who demonstrate autonomy, thus meeting the legal requirements to be considered “legal persons” with the capacity for appropriate rights like the right not to be kept in captivity. How would his arguments apply to pigs with human brains?

If even a single human gene is inserted into a nonhuman animal, the Nonhuman Rights Project will strongly consider filing lawsuits in which we claim that the resulting being is human. And we would have a good argument. And let the chips fall where they may.

I briefly addressed this issue in my testimony before a subcommittee of the House of Representatives in the 1980s. I said that this sort of fiddling would inevitably create legal problems that will make abortion and fetal rights a legal walk in the park.

The researchers at UC Davis say they will be terminating the tests on pig embryos after 28 days to see if any human cells have been created. But what if they find human brain cells? Right-to-life advocates believe that human life is sacred and that it begins at conception and may not be “terminated.” Author and Christian believer A.N. Wilson is adamantly opposed to creating human-pig chimeras:

If we place a value on human life, and the precious distinctiveness of being human, do we equate this with the fundamentally base idea that we want to continue forever at whatever cost?

… Would we be prepared to enter the amoral science-fiction world of [UC Davis] California, where pigs and humans have begun to be indistinguishable? Again, we should surely say ‘NO!’

There are activities in the laboratory from which decent people recoil. Think of the horrors perpetrated by Nazi and Soviet medics in the past.

In California, they have strayed into this kind of murky territory. We should not follow them … They might reply they are attempting to save human lives. We should reply that a life is not always saved by being preserved.

There is such a thing as decency. The creation of pig-human chimeras is a horror from which all decent people should recoil.

From the point of view of the animal who’s being exploited, of course, being retrofitted with a human pancreas, heart, brain or other organ isn’t really any worse than the horror of living at any research lab or factory farm where pigs, cows, chickens and fish are being re-jiggered every day so they’ll grow faster, fatter, tastier and more profitable.

This kind of research could have totally unforeseen consequences, like an uncontrollable virus.And profit is definitely the order of the day when it comes to growing human organs in other animals. Right now, in the United States, roughly 22 people die every day because transplants aren’t available. Globally it adds up to hundreds of thousands a year. (China does a roaring trade executing petty criminals and selling their body parts to foreign customers, but it’s not enough to supply the global market.)

You’d think that out of 7.3 billion humans, enough of us might be willing to donate our organs when we die. But no, our general response is, “Leave me out of this, even when I’m dead; just stick it to some other kind of animal.”

Those sentient animals may, however, end up sticking it back to us. One group of scientists warns that this kind of research could have unforeseen consequences, like an uncontrollable virus:

A deadly zoonosis could theoretically kill millions of people, and one might question whether the benefits of creating a new source of organs is worth outweighing the potential harms following from even a small risk of zoonosis.

(In her dystopian novel Oryx and Crake, Margaret Atwood explores some of the other things that could go terribly wrong when you create human-pig chimeras.)

None of this fazes Professor George Church, the world leader, pioneer and modern Dr. Frankenstein of mixing and matching human/nonhuman body parts. He tells the BBC that his work “opens up the possibility of not just transplantation from pigs to humans but the whole idea that a pig organ is perfectible.”

Yes, we may be bringing on a Sixth Mass Extinction of species, but no worries: In our infinite wisdom, we are making life more perfect than ever.