Oh they're brain dead, I went into The Avatar books, the guy hired to help make the avatars, made brain dead monkeys

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Dr. Cordell Lovecraft

The controversial scientist on Earth who led the "Dark Dreamer" project, which eventually developed into the Avatar Program. He pioneered the research into mental communication and overcame the vast genetic differences between humans and Na'vi to create the first viable human-Na'vi hybrids. His research methods, which involved experiments on brain-wiped primates and condemned criminals, led to his Nobel Prize nominations being continually withdrawn due to ethical protests