Final answer:
The primary difference between the foramen magnum in chimpanzees and humans is the location.
Step-by-step explanation:
The primary difference between the foramen magnum in chimpanzees and humans is Location. The foramen magnum is the large opening in the occipital bone of the skull through which the spinal cord emerges and the vertebral arteries enter the cranium. In chimpanzees, the foramen magnum is positioned further towards the back of the skull, while in humans, it is positioned more towards the bottom of the skull.