Short answer: to grind food in the early stages of the digestion process Long answer: Most likely, the root (pun?) of this question is "why do wisdom teeth erupt so late, and why are they often surgically removed?" Well, most likely, wisdom teeth erupt late in puberty, since that is when there is finally room for them in the jaw. Hence the name "wisdom teeth" since they arrive about the same time as young adulthood. Historically, teeth were used much more harshley than in recent times, and having a fresh set of brand new molars (wisdom teeth are the last set of four molars to erupt, one in each quadrant of the mouth, and complete the complement of 32 teeth in the adult) was a "good thing". The reasons that wisdom teeth can be a bit of a problem for some is that the size of the jaw has tended to decrease over generations, and for many, the last 4 molars to erupt just don't have much room. This can cause them to come in at the angle of the jawbone, and cause the lower wisdom teeth to acutally grow forward, rather than up, and push the existing molars, causing "impaction", and usually much discomfort. The uppers can do sort of the opposite and grow backwards, causing some similar, although less painful, symptoms. The most effective way to deal with this is to have them surgically removed by a oral surgeon, and put them under your pillow, for one last crack at a few coins from the toothfairy!

Wisdom teeth are used for the same thing the rest of your teeth are used for...to grind your food. But they were used more before the invention of fire and cooked food. The widom teeth are suited for grinding raw meat. But since we cook our food, we don't need them. Factoid#21 - Scientists say that eventually, we will lose our wisdom teeth since we don't need them. Evolution makes our mouths smaller as the wisdom teeth take longer and longer to grow in with each generation.