Final answer:
The trapezius muscle is responsible for enabling us to shrug our shoulders, as it is one of the posterior thoracic muscles that positions the scapula for this specific movement.
Step-by-step explanation:
A muscle that enables us to shrug our shoulders is the trapezius. The trapezius is one of the posterior thoracic muscles, which also includes the rhomboid major and rhomboid minor. When muscles like the rhomboids contract, they move the scapula medially, but it's the trapezius muscle that specifically allows the shoulder to move in a way that creates a shrugging motion. The anterior thoracic muscles, including the subclavius and pectoralis minor, perform different functions and do not facilitate shoulder shrugging in the same way. Similarly, the latissimus dorsi and pectoralis major are muscles involved in the movement of the humerus rather than positioning the scapula for a shrug.