Reoriented Use of Senses
Primates have certain senses that are
more important than others. The shape of the face and skull in primates
reflects the senses that are most important. It is important to realize
that the shape of an animal is related to the activities of the animal.
All primates rely more on sight than any other sense. As a result, primate
skulls are shaped in a way to maximize their vision. The eyes of primates
are located in the front of the face, rather than on the side of the head
as they are in dogs or horses. Due to the forward position of the eyes,
primates are capable of stereoscopic vision, and thus they have depth perception.
Stereoscopic
Vision
Hold your pencil or pen in front of the top of the computer screen. Look
at it first with one eye and then the other. Now look at it with both eyes.
Did you see a difference? What were the differences you noted?
Why would stereoscopic vision be important to a primate? Would it be important
to a cow? Can you think of any other animals who have stereoscopic vision?
Why would it help these animals?
The eyes of primates are oriented to the front and protected by a relatively
thick bone. The bone surrounding the lateral side and back of the eye is
called a post-orbital wall. The amount of boney wall surrounding the eye
varies between primates. In some primates, there is only a bar of bone on
the lateral side of the eye. This is called a post-orbital bar. In other
primates, the whole side and back of the eye is protected by bone, thus
they have a post-orbital wall.
Reduced Emphasis
on Smell
Since the main sense used by primates is vision, the physical features related
to smell are reduced in size. Primates have a reduced snout and the area
of the brain related to smell is much larger than that area in a dog. Primates
use vision and touch to explore their environment.
What senses do you think cats rely most on? Why?