Chimpanzee Brow Ridge & Beyond, Part I
Chimpanzees and humans have many things in common when it comes to facial expressions and facial structure; however, they also have many significant differences!
Below is a series of imagery focusing on an action affected by the prominent brow ridge seen in chimpanzees:
- cheek raiser – an orbicularis oculi (orbital portion) action
Observe the key differences and similarities.
Cheek Raiser Muscle & Brow Ridge Interaction
The diagram below breaks down the action of cheek raiser. Cheek raiser is driven by the contraction of the orbicularis oculi muscle – specifically the orbital portion of the muscle. Based on the placement of orbicularis oculi and the prominence of the chimpanzee brow ridge, chimpanzee cheek raiser movement is distributed differently compared human cheek raiser movement.
Observe how the bulk of cheek raiser occurs in the area outlined in blue. The prominence of the brow ridge causes the skin around the eyebrows to travel greater distances to get to the focal point of the cheek raiser contraction. This greater distance of travel creates a strong brow lowering effect when cheek raiser is activated.
The purple orbicularis oculi diagram shows how the outer portion of orbicularis oculi is distributed along the brow ridge. As described, this placement is likely what makes the downward brow pull so strong in chimpanzee cheek raisers!