We’ve created human-pig chimeras — but we haven’t weighed the ethics

I’m worried about a new paper in the journal Cell that details the creation of a human-pig chimera.

As a neuroscientist, I appreciate groundbreaking research at a purely scientific level and understand the hard work that goes into advances like this. But I also believe that science should be guided by ethics, and this work seems to be jumping ahead of ethical considerations.

In the new work, led by investigators at the Salk Institute, researchers injected days-old pig embryos with human pluripotent stem cells. By the time the fetal pigs were aborted, they had begun to grow partly human organs.

While this represents only a very preliminary step toward the development of human/nonhuman chimeras — the name comes from a mythical monster with the body and head of a lion plus the head and udders of a goat and a serpent for a tail — the goal of this and similar research is to generate pigs and cows with human organs.

Since cows and pigs are similar in size to humans, the human organs they grow could be harvested and transplanted into people. The key organs targeted in this research are the heart, liver, kidney, pancreas, lungs, and brains. These organs could also be used for research on human disease, development, and evolution. Pigs and cows would become, essentially, living containers for an unlimited supply of human organs.

Another expectation of this kind of research is that chimeras could serve as improved models for testing new drugs and boost the availability of tissue for research.

This work is part of a larger trend toward increasingly invasive and manipulative practices, from the domestication of animals for food thousands of years ago to the current culture of genetically modifying animals of many kinds: monkeys that show symptoms of autism, transgenic mice with altered vocalizations so they “stutter,” cows that produce “humanized” milk, and mice injected with human brain cells that cause them to learn faster.

The possibilities have many researchers giddy with excitement. But they also raise serious ethical dilemmas about the moral status of these part-human animals. Chimera test subjects must be human enough to serve as effective models for health research, but not so human that they qualify for protection from this research altogether.

We all want to alleviate human suffering. But the need does not dictate the solution.

As we continue down the path of this unprecedented manipulation of sentient beings and pour funding into it, we simultaneously limit funding for alternative solutions to our health problems, including prevention, consensual human trials, incentives for organ donation, microchip testing, and in vitro research. All too soon, when we look back on the path of chimeric research that we’ve chosen, we may not like what we see. But by then it will be too late.

A particular area of concern is the creation of chimeras with human brain cells. These organisms may be capable of self-awareness to the extent that they understand their identity and circumstances, which would produce unbearable suffering. Will we know when the subjective experience of such a being has crossed the generally accepted line of decency and morality? If we cannot say with certainty that this will never happen, then we need to stop this kind of research right now before we find ourselves in a world where there is no line.

These concerns about chimeric research add to the already potent ethical issues associated with mainstream invasive animal research. Tens of millions of animals are sickened, injured, genetically manipulated, and killed in biomedical labs every year, even as a robust body of evidence shows that some animals are more self-aware and emotionally and cognitively complex than we previously thought. That leads to the inescapable conclusion that we have already crossed a number of moral lines.

Chimeric research will only worsen the suffering of animals and move it into areas of unforeseen consequences, for which we are totally unprepared.

Unless we confront these issues now, we will find that our unrestricted efforts to save our bodies from sickness may come with an unwelcome cost: the loss of our souls.

Lori Marino, PhD, is the executive director of the Kimmela Center for Animal Advocacy and a former faculty member in neuroscience and behavioral biology at Emory University in Atlanta, Ga.