Some tricky questions ahead of us down the road:
If stem cells ever show promise in treating diseases of the human brain, any potential therapy would need to be tested in animals. But putting human brain stem cells into monkeys or apes could raise awkward ethical dilemmas, like the possibility of generating a humanlike mind in a chimpanzee’s body.
No such experiments are planned right now. But in a paper today in the journal Science, a group of scientists and ethicists is advising researchers to exercise care with such experiments, particularly if they should lead to a large fraction of a chimpanzee’s brain’s being composed of human neurons.
The group, led by Ruth R. Faden, a biomedical ethicist at Johns Hopkins University, acknowledged the view that monkeys and apes should not be experimented on at all, but nevertheless considered what kinds of research should be permitted if the experiments were required by regulatory authorities.
This will be a snarled and contentious debate.