 It's not 13 people. Your head weighs about anywhere from 11 up to 13 pounds. The bone it's balancing on is one ounce. So you have to take those 13 and multiply it by 16. That's how many people are balancing on top of one person in an analogy of how the head is balancing on top of the neck. Why did nature construct it that way? So that you have the incredible range of motion