The flat wisdom teeth are believed to have been used by early man to grind and eat hard grains, seeds and plant tissue, to digest the cellulose that compose a plant cell wall.

Over time, as modern man ate soft vegetables and cooked meat and foods, the jaws have become smaller. Evolution forgot that smaller jaws need fewer teeth.

The wisdom teeth – the last four teeth in each quadrant (the third molars) – continue to develop in human mouths although they may become extinct eventually because they are really unnecessary for chewing. Wait for maybe another million years.

So why are they called wisdom teeth as they don’t really make you any wiser? That is getting ahead of a most interesting story.

It is estimated that each year, 10 million wisdom teeth are extracted from nearly four million people in the United States alone – at a cost of nearly $5 billion.

Nearly two out of three of these extractions may be unnecessary and costly, causing mild to severe pain, swelling, bruising and absence from school or work.

Most adults have four wisdom teeth that appear between the ages of 17 and 25.

Extraction is usually done when wisdom teeth affect other teeth, becoming impacted as they develop sideways.

The most common form (nearly half) of impacted wisdom teeth is called mesioangular because the tooth is angled forward and towards the front of the mouth. When the formed tooth does not erupt fully through the gum line, it is called vertical impaction (which affects about four of 10 cases).

Less common (at six percent of cases) is distoangular impaction when the tooth is angled backward and towards the rear of the mouth. Rarer (3 percent) is the horizontal impaction when the tooth is angled fully 90 degrees sideways, growing into the roots of the second molar.

If impacted, the wisdom teeth that are still completely encased in the jawbone are called a bony impaction. If they have erupted out of the jawbone but not through the gum line, they are called soft tissue impaction.

Wisdom teeth are extracted when they have become impacted or when not pulling them out may cause infections which are painful and potentially dangerous if untreated.

Infections are caused by food particles easily trapped in the jaw area behind the wisdom teeth. These areas are difficult to reach by regular brushing and flossing, which then become ineffective.

Wisdom teeth are also removed when they are misaligned. These teeth rub against the tongue or cheek and cause pain. Potential crowding or malocclusion of the remaining teeth occurs when there is not enough room on the jaw or in the mouth.

Extracting disease-free wisdom teeth is not advisable. Extraction is beneficial if caries or cavities are present in the adjacent second molar, or if gum pockets are present.

The National Institute for Health and Clinical Excellence, of the United Kingdom’s National Health Service, recommends that impacted wisdom teeth that are free from disease should not be operated on.

The US American Association of Oral and Maxillofacial Surgeons recommends that third molars be removed in patients who, in the opinion of their family dentists, suffer from gum infections.

It advises that the third molars of these patients be removed in young adulthood to avoid the complications that may occur when these molars have grown to maturity and when there is a greater likelihood of nerve damage and other potential concerns.

Meanwhile, the American Public Health Association believes the removal of wisdom teeth, like the removal of any teeth, should be based on evidence of diagnosed disease or demonstrable need.

So why are they called wisdom teeth? The best explanation cited by Yahoo Answer comes from a medical student at Washington University in St. Louis: because they appear later than the other teeth, “at an age where people are supposedly wiser than as a child, when the other teeth erupt.”

The Turkish language refers directly to the age at which wisdom teeth appear and calls it 20 yas disi (20th year tooth). In Arabic, its name is Ders-al-a'qel, literally meaning “The tooth of the mind.”

In Korean, its name is Sa-rang-nee (love teeth) referring to the young age and the pain of the first love. The Japanese call it Oyashirazu, “unknown to the parents,” from the idea that they erupt after a child has moved away. In Chinese, the term is Zhi Chi, a word for wisdom (Zhi) and tooth (Chi).

The Indonesian term gigi bungsu refers to the "youngest child". Thais describe it as fan-khut or "huddling tooth" due to its shortage of space.

In many Spanish speaking countries, it is called the "molar of judgment" (muela de juicio). This is because when they appear, the person is considered to have a better judgment than that of a child.

A similar phrase commonly used in Italian is dente del giudizio, or judgment tooth.