The following 2005 article covers scientific experiments that are placing human brain cells into animals, including mice and sheep:
"Creating 'human-animals' for research; Ethics report endorses mingling human cells with lesser beings"
This is the "slippery slope"!
A scientific committee which approved this research "recommended closely monitoring the mice's behavior and immediately killing any that display human-like behavior." They are acknowledging this is possible!!! All they are doing is watching for outward signs of human behavior while they place human brain cells in these animals? What if these animals have the thoughts of humans but these thoughts are not translated into outward physical movements what could be detected?
Put more frankly: it could be like being trapped in an animal's body.