3 cheers for the pig man

It may not always feel like it, but we live in an age of miracles. The most recent: the first successful transplant of a heart from a non-human mammal to a human being.

This was not the first successful xenotransplantation of a working organ. Last year saw the first successful transplant of a genetically-modified pig's kidney into a human being. But the recipient, in that case, was also a donor, someone who was legally dead and who had offered his organs for donation. Since these proved unusable, his family instead donated his entire body for research purposes to receive the pig kidney to study whether it would be rejected.

Last week's operation took the prospects for such surgeries a giant step further. David Bennett Sr., a man with life-threatening heart disease, did not qualify for a human heart transplant. So he was offered an experimental operation that gave him a heart from a genetically-altered pig. So far, the operation has been a success, and if that continues to be the case, then it is reasonable to hope for a solution to the ongoing shortage of organs, and a major leap forward for human longevity and health.

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You'd think everyone would rejoice at the thought. But I suspect not everyone will.

What makes this kind of xenotransplantation possible is the rapidly advancing science of genetic manipulation. The pig whose heart was implanted into Bennett had been modified in multiple ways to prevent its organs from being rejected by a human recipient, including by having several human genes inserted into its genome. That kind of blurring of the lines between human and non-human is something that I can recall ringing alarm bells in a certain corner of the religious right more than two decades ago:

The quote is from an essay by Jody Bottom called "The Pig Man Cometh." The particulars of that 2000 experiment were radically different from the ones that made it possible to save David Bennett's life last week — they involved the insertion of nuclei from a human fetus into a pig's egg cells, not the editing of an animal's genome to insert human genes. But research into such "chimeras" that combine human and animal cells continues, and the visceral horror Bottom evinced was widely enough shared that their prohibition was part of President George W. Bush's second term agenda and was attempted again only last year.

Should we dismiss these concerns as mere gut revulsion or the product of religious dogma? I'm not so sure. Inserting a few human genes into a pig to prevent organ rejection raises no obvious ethical concerns. But what about combinations, whether produced by genetic engineering or the insertion of human stem cells into animal embryos, that have more substantial human characteristics? What about editing our own genes? Surely we do need ethical guidelines to prevent us from erasing the boundaries of humanity?

Indeed, we do need parameters — but I suspect that way of framing the issue isn't going to be too helpful in constructing them.

The notion that Homo sapiens are utterly separate from the rest of the animal kingdom has been known to be false since Darwin's time, and the more we learn about our origins, the more false we discover it to be. Not only are we descended from non-human species, but we carry with us the genetic legacy of other archaic lineages — Neanderthals and Denisovans — whom our ancestors did not simply replace but interbred with. And human beings have continued to evolve and differentiate over time, with different populations developing the ability to digest lactose, tolerate life at high altitudes, and resist malaria, to pick just three examples. We are not all the same as each other, nor are we radically distinct from other animals. We're certainly not the only featherless biped. What, then, makes us human?

I don't think there is a simple answer to that question, and pretending there is will neither make it so nor prevent us from doing evil. Drawing hard lines around the human was crucial to establishing the regime of rights that we justly cherish; it was also strongly implicated in the development of race-based slavery which trapped Black people outside of those same hard lines.

If we are to be guided by anything beyond pure consequentialism, then, I suspect that guidance will have something to do with our relationship with the other with whom we are concerned. Whether that other is an embryo or a dying person or a pig, our openness to the reality of their experience, however similar to or different from our own, and to the web of relationships within which they are embedded, will do more to keep us from horror than a fixation on their proper status.

I'm glad to live in an age of miracles, and I want to live to see more of them. Prometheus' fire should never be snuffed out — which means it must be well-tended.