The Real Reason Pig-Human Chimeras Make Ethicists Uncomfortable

I recently came across a story about a controversial new science project: growing human organs inside pigs, cows, and sheep. It works by first removing the gene that a pig needs to make the desired organ--say, a pancreas. Once the scientist has a pig embryo lacking that gene, he injects human stem cells into the embryo, hoping that the human stem cells will fill in the gaps and make a human pancreas. The ultimate goal is to transplant those organs into humans.

The project is so controversial that the National Institutes of Health has refused to fund it. The researchers are relying on private donors. Critics of these experiments say they are too risky because there is no way of knowing where the human stem cells will go. Will they just become a pancreas? Or could they become a brain? And if they become a brain, will the pigs who house them have human consciousness?

Scientists working on the project are fending off these critiques by proceeding slowly and with extreme caution. Right now, they are only letting the embryos develop for 28 days inside a pig's uterus before removing them to see whether the cells are differentiating the way they want. But they plan to continue changing their gene modification process until they can successfully get a human organ to grow inside a non-human animal.

I think the real reason these experiments scare us is that they will force us to confront the question of what makes humans different from animals. Bioethicist Jason Robert, who was interviewed by NPR, offered one possible answer: our humanness lies in our DNA. If that is the case, and you put human DNA in a non-human animal, you could blur that line between humans and other species.

And once you consider that possibility, you get into even scarier questions. Could you give a pig so many human characteristics that you can't justify experimenting on it anymore? Could you give it so many human characteristics that slaughtering it to give the pancreas inside it to a dying person would not be a sacrifice for the greater good, but rather, murder?

This is the reason that the NIH has forbid funding this research. They worry about the ethical consequences that could result from it. But I think you can take the concerns one step further, and ask what this research reveals about our current ethical standards. If it is possible to combine the DNA of a human and the DNA of a pig into one creature, does that mean the pig was never really that different from a human? And if so, what right do we have to experiment on it?

We often justify our domination over non-human animals by saying that no other species possess a so-called "human consciousness." Bioethicists worry this type of consciousness could appear in pigs if those human stem cells develop into brain cells, but to assess this possibility, we would need a clear definition of what human consciousness is--an itemized list of its characteristics. That, I think, is extremely difficult to come up with, given that many non-human animals are capable of items we would put on said list: communication, self-recognition, grief, and empathy.

Anybody who has had a beloved pet has surely seen their animal companion display some form of relatable consciousness. Your dog comes and lies beside you when you're feeling sick. Your cat comes to cheer you up when you've had a bad day. Is this purely a survival instinct--the concern that if a caretaker is not well she can't provide food and water--or is it empathy, a trait which we might think is purely human?

My father tells a story of taking me to the zoo when I was three. He stood with his hand on my back as we looked at a gorilla and her baby on the other side of a glass wall. The mother gorilla looked back at us and drew her baby close to her, mirroring us. I was too young to remember it, but my father says there was a recognition of parenthood between him and the gorilla--a moment in which they were more the same than different.

When we so frequently see evidence of emotion, communication, and even empathy in non-human animals, it becomes more difficult to justify our domination over them. What gives us the power to designate pigs as the bearers of our organs? Will we acknowledge that their bodies are similar enough to ours to harbor our own beating hearts, while maintaining that their brains are different enough to justify slaughtering them?

And that leads into the final question: Do these experiments not only make pigs more human, but also, perhaps, make humans less human? The word "humane" is synonymous with compassionate and merciful, as if we humans are the only animals who have the mental capacity to treat other creatures justly and kindly. Will we lose that quality if we continue to experiment on less powerful beings for our benefit?

Or, have we already lost it?