Explain why wisdom teeth are vestigial structures?

Your wisdom teeth are flat and are used for grinding. Evolutionists believe that our ancestors used them to grind and eat hard grains and seeds. Since modern mankind mainly eat vegetables and meats and often cook their foods, it is thought that they have receeded as they are not needed anymore. Evolution would thus dictate that they will eventually be lost altogether. Obviously there is disagreement on this topic depending on you beliefs.

I should add that it is not the wisdom teeth as such that is the victim of evolution. Since there has been a marked change in our dietary habits our jaws themselves became smaller, but somehow the evolutionary selection process forgot, that smaller jaws need lesser number of teeth.! The result is what we have today, smaller jaws and more teeth.So the last four teeth in each quadrant ( the third molars) have a difficult time wriggling out. It is true that we really don't need them for chewing.We may lose them all together in another million years.