Understanding animal signs was an ancient science. In those days people lived in very close quarters with animals, both domesticated and wild. Hence they had opportunity to understand the animal signs clearly and related it to understanding the environment better. For eg. when does dragonfly fly a lot..? when there's a lot of moisture in air and about to rain. So simple. When lizards make sound, they do either to avoid fighting or for courtship. In either case they are asking for their acceptance. So when people say something and lizard makes sound, people mis-interpret it as acceptance. lizards make sound asking for acceptance. We also had various beliefs in the past based on our environment at that time. You are not supposed to hit on top of the head (it means you are unprotected and face death). You are not supposed to wave off with your right hand (lakshmi will leave you), but you can do so with left hand or left foot (poverty leaves you). You are not supposed to hit your chest...