There a depression on the sides of the skull

The depressions on the sides of the skull are known as the temporal fossa, and they house the temporal muscles. The temporal fossa is located on each side of the skull, and it is a shallow, concave region. The temporal muscles, specifically the temporalis muscle, occupy this space.

The temporalis muscle is one of the muscles involved in the movement of the jaw. It originates from the temporal fossa and attaches to the mandible (lower jaw). Contraction of the temporalis muscle allows for actions such as closing the jaw during chewing and speaking.

The shape and structure of the skull, including these depressions, are a result of the complex interplay of evolutionary and functional factors. The skull has evolved to accommodate the brain, protect sensory organs, and provide support for the muscles involved in various functions, including mastication (chewing) and facial expression. The temporal fossa, in particular, reflects the adaptation of the skull to the biomechanics of the jaw muscles and their functions in daily activities.