Why do we have wisdom teeth?

Adults have 32 teeth. The last teeth to develop are the third molars, known as wisdom teeth. Before modern times, the diet of ancient men was very coarse. This chewing mechanism stimulated jaw growth so there was enough room for wisdom teeth to erupt fully. With our modern refined diet and modernized agriculture, our jaws are not as large as our ancestors; therefore, wisdom teeth often do not have enough room to erupt and are termed "impacted".
       Hunter-Gatherer   vs    Modern Man            
Notice stronger chewing muscles and more prominent jaws in ancient man.

Anyone who is in danger of developing impacted wisdom teeth (third molars that only partially erupt or get trapped or stuck in the jaw) should have them removed so that they do not damage adjacent molars and cause other oral problems.
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Click here for more information about Wisdom Teeth and their removal