World’s first chimeric human-monkey embryos created by a team of scientists from U.S., China, and Spain

A drive to make experimental models to help scientists better understand early development, devise new treatments for human disease and possibly find methods to grow organs for transplants inside other animals, such as pigs or sheep. Such chimeras can be used in experiments that can’t be done with human embryos, for example, but combining human cells with those of primates ushers in new and urgent ethical concerns.

To be clear, the work, published in the journal Cell, is in very early stages. The team did not create a living, breathing part-human animals. They created very early embryos and never implanted them into the uterus of any animal. Concerns about human-animal chimeras center on what Stanford bioethicist and legal scholar Hank Greely calls “brains, balls, and beauty” — worries that an animal could look at all human, be born with a human brain, or be able to reproduce.

This experiment carried none of those risks but makes it clear that the time to start discussing the ethics of human-animal chimeras is now. “It’s a first-in-kind experiment”
Read more: STAT News