Quick Answer. The function of motor neurons is to release the neurotransmitter acetylcholine, which are released at a junction known as the neuromuscular junction, that bind to postsynaptic receptors, causing the muscle fiber to respond and result into a muscle movement.
The frontal lobe is what really sets us apart from animals, which controls one important aspect of humans: Self awareness. The thinking in terms of I am.. Animals don't do that. (although they DO have sex for pleasure.
The species theory, polygenism, held that human races were of different lineages and suggested a hierarchy outlined in the Chain of Being that positioned Africans between man and lower primates.