Final answer:
The vocal tract, with a descended larynx and structured tongue, and brain regions like Broca's and Wernicke's areas, are crucial for human speech production and comprehension.
Step-by-step explanation:
The two most important parts anatomically speaking for human speech are the vocal tract and specific areas of the brain. The vocal tract has a descended larynx, which is essential for producing a wide range of sounds, and the hyoid bone that supports the tongue's movement. Moreover, humans have precise control over their breathing, which is vital for speech. Anatomical changes in the vocal tract, such as the descended larynx and the structure of the tongue, have enabled the complex speech capabilities of modern humans. In terms of brain structure, regions like Broca's and Wernicke's areas are crucial for speech production and comprehension, respectively. These areas are typically found in the left hemisphere for right-handed people (and in the right hemisphere for left-handed individuals), reflecting the brain's role in linguistic functions.