Dead on. There is very likely some very specialized neural motor control circuitry that humans use for speech that is missing from other primates. If you consid

Dead on. There is very likely some very specialized neural motor control circuitry that humans use for speech that is missing from other primates. If you consider, for example, dexterous finger movements, there is a strong correlation between the number of direct corticospinal [1] projections and degree of finger dexterity that the species exhibits. Rodents and many other mammals have no projections at all. Monkeys have some; humans have many [2, see fig 1]. So which primates have corticospinal projections for their vocal cords? Okay, that's actually a trick question because the vocal cords are innervated via cranial nerves emanating from the medulla [3], rather than via spinal cord. However, in humans, there are direct monosynaptic projections from cortex to these medullary motor neurons. These projections do not exist in macaques (and presumably not in other monkeys) or in chimpanzees [4, see fig 2]. I'm not sure if it's known whether gorillas or orangutans have them. 1. https://en.wikipedia.org/wiki/Pyramidal_tracts#Corticospinal_tract 2. http://www.nature.com/nm/journal/v13/n5/full/nm1595.html 3. https://en.wikipedia.org/wiki/Nucleus_ambiguus 4. http://www.sciencedirect.com/science/article/pii/S095943881400107X