Bits of electricity shot through Mr. P’s flesh. Layer upon layer of subcutaneous fat unraveled, filling the operating room with a pungent, metallic smell, like singed hair at the neighborhood barbecue. After a few minutes, the pearly white sternum bone protruded before a vein split, filling the operative field with blood.
Zap! The chestnut juice turned into a crackling black mass.
Transplant surgery is all about timing, says Dr. Brandon Guenthart, a cardiothoracic surgeon at Stanford University School of Medicine. Anesthesiologists put the patient to sleep after the retrieval team confirms that the donor’s heart looks good. Two surgeons begin surgery an hour before the donor’s heart arrives at the hospital. They don’t start cutting out the patient’s heart until the donor heart has landed safely at the local airport.
What if the plane crashes? “Knock on wood,” Guenthart says. Unfortunately, there is no wood in the operating room.
I was at Stanford Hospital watching this heart transplant because of my interest in David Bennett, a 57-year-old man who died in March. On January 7, 2022, at the University of Maryland Medical Center, Bennett received a remarkable heart transplant from an unusual donor: a genetically modified pig.
Surgeon Muhammad M Mohiuddin leads a team placing a genetically modified pig heart into a storage device at the Xenotransplant laboratory before its transplant to David Bennett on January 7. Photo: UMSOM/Reuters
A record 41,354 person-to-person organ transplants were performed in 2021, but more than 100,000 Americans are still on the transplant list. Every day, 17 people die waiting because there simply aren’t enough organs to go around.
Xenotransplantation – or the transfer of cells, tissues and organs between species – promises to solve this shortfall and change the way we think about human longevity.
Lost in this limitless potential, however, is the significance of the division between humans and animals. People walking around with pig organs mixed into their bodies – kind of like human-animal cyborgs – might seem dystopian. And since the zoonotic virus Sars-CoV-2 has killed more than 6 million people, disrupting the human-animal interface may just promise more disaster.
This tortuous relationship is nothing new, but it’s often sanitized and hidden from view—think grinning cows on milk cartons and secret animal research bunkers. Many questions remain open, starting with the most complex of all: what does it mean to be human?
People are animals. But animals are not people. Yet our history is replete with a cultural imagination of hybridity. The ancient Egyptian god of the sky Horus is depicted with the head of a falcon, and the goddess of war Sekhmet with the head of a lioness. Similarly, the Hindu god Ganesha was beheaded and then resurrected with an elephant’s head grafted onto his body. In ancient Greece, fantastic creatures roamed the myths, from the bull-headed Minotaur to the snake-haired Medusa.
Within this wealth of possibilities, the International Association for Xenotransplantation has chosen a more obscure mascot: Lamasu, an Assyrian deity with the body of a bull, the wings of a bird, and the head of a man—fundamental wisdom.
Xenotransplantation, as a research field, starts with just cells and tissues. In the 17th century in France and England, animal blood was transfused into humans to cure a variety of medical conditions. A spiritual significance was attached to the act: “Since Christ is the Lamb of God,” wrote one recipient in a letter to the Royal Society, “the sheep’s blood possesses[es] symbolic connection with [his] blood”. One patient’s solid fever was supposedly cured, as was another patient’s paralysis, but at least two others died soon after these “xenotransfusions.”
The ancient Egyptian goddess of war, Sekhmet. Photo: Smith Collection/Gado/Getty Images
Other early xenotransplants will follow, including those with bone, cornea and skin. Perhaps most scandalously, French surgeon Serge Voronov transplanted slices of chimpanzee and baboon testicles into men and monkey ovaries into women to rejuvenate his patients’ “lust for life.” Thousands of these surgeries have been performed worldwide, but any reported benefit, such as reduced fatigue or increased sex drive, is likely just a placebo effect and fades quickly.
While cell and tissue xenotransplants have been performed for centuries, whole organ transplants are more difficult to figure out. Suturing all blood vessels is difficult work. You must place two floppy tubes together “mouth to mouth”, tying them tightly enough so that the patient does not bleed, but delicately enough that there is no major clotting.
It was a Nobel Prize-level problem that French surgeon Alexis Carrel solved with a tiny embroidery needle and fine silk thread, and was recognized for it in 1912. He is sometimes known as the father of transplant surgery.
Half a century later, in 1964, University of Mississippi surgeon James Hardy attempted the world’s first heart transplant, transplanting the heart of Beano the chimpanzee into the chest of the rapidly deteriorating 68-year-old Boyd Rush. Rush only survived 90 minutes, with the chimpanzee’s heart not offering enough support and the rejection quickly shutting down his body.
It was the Baby Fae who really raised the stakes for xenotransplantation. She was a 12-day-old baby with hypoplastic left heart syndrome, a congenital abnormality in which the left side of the heart is part of its full shape. The condition was a death sentence.
So, in 1984, surgeons at Loma Linda University in California transplanted a walnut-sized baboon heart into Baby Faye’s chest. The conditions were almost perfect. The heart was oversized, the Baby Fae’s immune system was immature (and sympathetic), and the immunosuppressive drug cyclosporine could suppress the attacks on the baboon’s heart.
After the surgery, Baby Fae looked fine. Resting in her crib with a gauze-covered scar criss-crossing her chest, she was “just swallowing her formula” and howling with a “lustful cry,” according to a hospital spokeswoman. The hospital also released photos of Baby Fae “talking” to her mother, the phone receiver larger than her entire torso.
She died 21 days after the operation, her immune system refusing to accept the new baby-baboon hybrid. Outcry from doctors and the public soon followed, with animal rights activists protesting and bioethicists publishing articles such as “Baby Fae: The ‘Anything Goes’ School for Human Experimentation.”
Xenotransplantation died with the Baby Fae, if only for a little while.
“During surgery, when the drapes are in place, it’s not really a person,” Guenthart said. “It’s a task.”
Technically speaking, a heart transplant is quite easy. It takes just five incisions to cut out the failed heart and just five ties to put in the new one. Electrocautery in one hand, scissors in the other, you usually cut the superior vena cava first—the vessel that returns blood to the heart from the head, neck, arms, and chest—because it’s the most accessible structure.
Next is the inferior vena cava, which returns blood from below to the south, but is somewhat difficult to access. So, you cut off part of the right ventricle of the heart where this vessel flows.
Next come the aorta and pulmonary arteries in fairly simple, straightforward cuts. The pulmonary veins are more difficult because they are four delicate vessels that are almost impossible to reconnect. The way to do this is to lift the heart up and cut a rim of left heart tissue underneath. “You create a swimming pool or a little crater,” Guenthart said. He paused. “This is just me giving a description. They don’t actually call it a swimming pool.
Whether you are transplanting a human heart or a pig heart into someone, the steps are essentially the same.
“If you ask 99 doctors out of 100, they won’t be able to tell you if they’re looking at a human chest or a pig chest,” Gunthart said.
Pigs are dirty animals, as the conventional wisdom goes. Judaism and Islam forbid the consumption of pork and other unclean meat. The “cops are pigs” insults are undeniable. And in the Odyssey, the sorceress Circe turns Odysseus’ greedy men into pigs.
Pigs stand in a barn at the Badersfeld marsh test farm in Oberschleissheim, Germany. Photo: Lucas Barth/Reuters
Pigs are also very intelligent animals capable of showing emotions. By about 11,000 years ago, wild pigs may have become domesticated, recognizing the benefit of association with humans. They love to play fetch, can navigate mazes and can outsmart dogs and chimpanzees, according to their IQ tests.
After the Baby Fae experiment, primates fell out of favor for xenotransplantation, and pigs became the new model organisms that researchers had to develop.
If you ask xenotransplantation experts today, they’ll give you a whole list of reasons why pigs are better than baboons: they’re easier to genetically manipulate, they can be grown in a sterile environment to reduce infections, and they can be grown to produce organs of any required size.
It’s a well-packaged narrative, but Dr. Brad Bolman, a historian of science at the University of Chicago, argues that sheep, goats, or some other animal could be considered suitable instead. At first, Bolman said, “it wasn’t obvious that pigs were the right substitute for nonhuman primates.” But when pigs were selected, scientific ideals were retroactively constructed to appear to be the clear choice all along.
Bolman says pigs were chosen because it was socially and economically convenient. They produce large litters quickly, with piglets reaching human size in six months. There is also an almost unlimited supply of them – 700 million worldwide – and as…
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