Dentist Oxford Why Do We Have Wisdom Teeth?
Nearly every adult who has wisdom teeth erupt has to have these teeth removed. There is simply not enough room in our mouths to accommodate these teeth that come in several years after our adult teeth have erupted. If these teeth have to be removed, why do we have them in the first place?
Anthropologists that have studied human evolution and culture believe that the third set of molars called wisdom teeth were common in our early ancestors who needed to digest coarse foods such as nuts, roots, and meat. These foods require more chewing to process and caused excessive wear on teeth so more teeth were needed to accommodate the diet. 
Do I Still Need Them?
Today, these teeth are considered vestibule organs, meaning that they have become useless to humans. Wisdom teeth still form in our mouths though beginning around age 10 for most people. They take 10-15 years to completely develop and erupt with most people experiencing them coming in between the ages of 17 and 25. Not all people get their wisdom teeth though and some only get 1 or 2 of them. There are also very rare occasions where people can have more than 4 wisdom teeth develop. There is no scientific evidence that shows exactly why there is variation between people except that evolution has a part to play. 
Human jaws have become smaller during the evolutionary development of humans and there is no longer any room in most people's jaw for these extra, and useless, teeth. Because of this, wisdom teeth can become impacted and very painful when they begin to erupt. Many times, these teeth can only partially erupt which can cause infections and decay due to food being caught in the tooth and gum area. Cysts can also form around the soft tissue of an impacted wisdom teeth that can lead to bone deterioration or damage to other teeth. Not all wisdom teeth will need to be removed, however with so many complications that can come from these teeth, the American Association of Oral and Maxillofacial Surgeons say that nearly all people will need to have them removed eventually. Some dentists and surgeons will be able to see your wisdom teeth forming through x-ray and recommend removing them before eruption so as not to cause any complications that can be more painful or harder to treat in the future.