Hey, Dave.
What do you mean by "different roles?"
My educated guess is that the difference in pitch is attributed to the territorial behavior of our primate ancestors.
Many animals, primates included, are very territorial. One way of saying "this is mine" is by making loud vocalizations.
A deeper vocalization (lower frequency) will travel farther in a humid forest than a high pitch voice.
In monkeys and apes, it is usually the male that makes threat displays or calls to make his presence known. Intuition tells me that this dimorphism evolved as a result of the "protector" role of the males. Is this what you meant?
Also, the "alarm call" is not uncommon in the animal kingdom. Most primates are very generalized creatures so it makes sense that they share various behaviors with other animals (especially other mammals). Many monkeys will vocalize to alert others to danger. I would imagine that the startle response would have been in place in early primates before apes, hominoids, and hominids evolved - so before there were any apes for sexual dimorphism to exist in.
Kinda off topic?
I don't know if it is much off topic, but it is definitely getting deeper than can be easily explained in a post.
Your educated guess is valid
However, there is more to it than that
Remember, these questions about whether one behavior/physical
characteristic came "first" or if they developed/evolved concurrently are
VERY tough (if not impossible) to test
Did these differences
start out as primarily territorial displays and be found later to serve another evolutionary purpose?
Were the gender role differences present BEFORE hominids became "hunter/gatherers"?
When did hominids cross the line between being "forager/opportunists" to become "hunter/gatherers"?
Unfortunately we do not have those answers
I am going to stay at the "time-frame" of the hunter/gatherer
Males did most of the "hunting" (killing larger animals)
This required more upper body strength and the ability to manipulate three dimensional space
They moved in larger groups, with longer distances between individuals
Males developed larger chest cavities to "support" the upper body strength and to provide for larger lungs to support stamina
Along with this, the larynx expanded and moved lower in the throat
This allowed the vocal chords to be closer to the "echo chamber" that the chest cavity acts as and to vibrate at a lower pitch
These changes gave the males the lower and louder voice that allowed them to cooperate in hunting in the jungle
This cooperation led to more success
Females did most of the "gathering" (fruits, vegetables, grubs, etc.)
They moved in small groups, with short distances between individuals
Their communication did not have to cover the same distances as the males' did
Gathering does not require the same upper body strength
The rib cage remained thinner
The larynx remained high in the throat
This caused the female voice NOT to carry a long way
They did not want to attract the attention of predators
You can easily test this concept by making a sound and moving your larynx higher and lower in your throat
Don't try to change the pitch
Just change the position of the larynx
There are some other gender differences that are believed to be based in these differences. (e.g. the number of words we use to express ourselves)
Yes. This is extremely superficial and controversial.
However, it is already more than one wants to type into a post and/or read in a post for most members
Peace,
dave
