Munoz, Canada Research Chair in neuroscience at Queen’s University, has reported his work using brain molecules. Others are implanting monkeys with fragments of human brain tissue extracted from people who died with Alzheimer’s.

Now, however, some are going further, and proposing the creation of human-monkey chimeras — part-human beings with entire portions of the brain, like, say, the hippocampus, entirely human derived.

For Munoz, the idea of biologically humanizing large portions of a monkey’s brain is seriously unnerving. “To be honest, it just really ethically scares me,” he said. He believes in animal research as a fundamental way of understanding how the brain works. However, “For us to start to manipulate life functions in this kind of way without fully knowing how to turn it off, or stop it if something goes awry really scares me.”

However, in a new book on the science and ethics of chimeras, Yale University researchers say it’s time to explore, cautiously, the creation of human-monkey chimeras.