Human-Primate Chimera

When most people hear the term “chimera,” they think of the mythological fire-breathing creature – part lion, part goat and a little bit snake. But in genetics, the term actually applies to any organism with cells from more than one genotype. In fact, in recent decades, experiments have created mouse-rats, sheep-goats and chicken-quails. Now, scientists in China have reported creating human-monkey embryos.

Dozens of macaque embryos were injected with human pluripotent stem cells, which are capable of developing into any type of cell in the body. The human cells were tagged with fluorescent markers to track where they ended up as the embryos developed. Although human cells were present in all four types of tissue present in mammalian embryos, they made up no more than 7 percent of any given type of cell. None of the embryos survived more than 20 days.

Research such as this, while banned in the United States, could shed some light on embryonic growth and its role in congenital diseases. Chimeric animals could also someday be used to provide organs for transplant. Still, the moral and ethical implications of creating human-animal hybrids bears a great deal of serious consideration.