Final answer:
The landmark discovery of mirror neurons in monkey brains helped expand our understanding of the neurology behind imitation and language capabilities, a finding that has implications for research in both primatology and neuroscience.
Step-by-step explanation:
A major discovery in a monkey system of Huntington's Disease (HD) was the identification of specialized neurons known as mirror neurons. These neurons were first observed in monkeys and are believed to play a crucial role in the ability to imitate and understand the actions of others, which could be a fundamental prerequisite for language development.
Due to the invasive nature of the neurological studies that revealed these neurons, similar research cannot be ethically conducted on humans, although neuroimaging suggests that a similar system exists in the human brain.