What are the ethical concerns?
For one, aspects of the technology make some people uneasy, said Jason Robert, a bioethicist at Arizona State University.
Before human stem cells are inserted, the animal embryos undergo “gene editing.” That capability — altering the genes of an embryo — raises red flags for some, Robert said.
And then there are the chimeras themselves. Some critics, Robert said, object on the basis of “human dignity” — arguing that transferring human characteristics to animals could denigrate what it means to be human.
Other concerns are less philosophical. Human stem cells can, in theory, grow into any mature tissue. So, some ask, what if the cells formed human sperm or eggs in the pig, or another animal?
Robert mentioned another issue some have raised. Could the stem cells get into the brain of a developing animal and endow it with human-like mental abilities or consciousness?
To Robert, that worry is a “peculiar” one. But he said the bigger point — that human stem cells are powerful, and research needs to proceed cautiously — is well taken.
“This has to be a slow road,” Robert said. And he praised the new research for its execution.
“These are incredibly careful scientists trying to do good work,” Robert said.