Does everyone has wisdom tooth?

Some may grow less than 4 wisdom teeth or none at all. People who are naturally missing one or more of their wisdom teeth is an example of hypodontia.

Why are some people missing of wisdom tooth?
Some studies show some links between evolution and wisdom tooth. Millions of years aogo, our ancestors (the prehistoric and early, primitive men) have really large jaws because of their tough diet such as raw meats. Their jaw could fit in all 32 teeth, including the wisdom tooth. Also their teeth wear out easily because of their tought diet. So, the third molar was seen as a back up when other molar teeth have worn out. In the process of evolution, our jaws get smaller (because our diet are now softer and simpler, like cooked and processed food) and allowing lesser space for the third molar.