Non-verbal communications are one of the very few things in a man's arsenal that should be well accounted for. by that I mean the subtle cues that can give off what you really intend from what you supposedly intend. A man's posture can give off a lot of important hints, especially in the eyes of women. Most notably his; confidence levels, self-respect, outgoingness and perceived place in a group.
Most guys with a poor posture have generally low levels of the described four traits and are most likely headed to a certain death. By death, I mean "getting weeded out of the gene pool". A lot of them probably have few friends, afraid of contact with the opposite sex, on the computer a lot, low self-worth, unfit, lonely, and are sometimes in a state of denial.
Why you should have good posture
Men with good posture have usually the opposite of the traits that I have just described. It does have a profound effect on one's aesthetics. If you have bad posture you better straighten your back as people will not only will people take time to listen to you if you have something to ask them but it also makes you more approachable. Thus increasing your chances with women.
One way of straightening one's back:
Imagine that there's a long thread in your spinal cord and it's being pulled from up in the sky somewhere. And every time you walk, your back is being pulled like a puppet on a string,