Wisdom tooth is the correct answer as it is a vestigial organ in humans.

Wisdom teeth, also known as third molars, are the last set of molars to emerge in the human mouth. They usually appear between the ages of 17 and 25, which is considered the "age of wisdom," hence the name.

However, over time, human jaws have become smaller due to changes in diet and evolution. As a result, there is often not enough space in the jaw to accommodate the wisdom teeth properly. This leads to a variety of dental issues, such as impaction, crowding, and misalignment.

1. Wisdom teeth are vestigial organs:
- Vestigial organs are those that have lost their original function through evolution. They are remnants of structures that were once functional in ancestral species but are no longer necessary in the present form of the organism.
- In the case of wisdom teeth, they were useful in early humans who had larger jaws and a diet that consisted of coarse, rough food that required extensive chewing.
- However, with the development of modern cooking techniques and a softer diet, the need for an extra set of molars became obsolete.

2. Problems associated with wisdom teeth:
- The reduced jaw size in humans often leads to the improper eruption of wisdom teeth. They may get stuck partially or completely below the gum line, which is known as impaction.
- Impacted wisdom teeth can cause pain, swelling, infection, and damage to adjacent teeth.
- They can also lead to crowding of the other teeth, pushing them out of alignment and causing bite problems.
- Due to their location at the back of the mouth, wisdom teeth are difficult to clean properly, increasing the risk of tooth decay and gum disease.

3. Treatment options:
- Due to the potential problems associated with wisdom teeth, many dentists recommend their removal, especially if they are causing pain or other dental issues.
- Wisdom tooth extraction is a common dental procedure that involves the surgical removal of one or more wisdom teeth.
- The extraction can be done under local anesthesia, sedation, or general anesthesia, depending on the complexity of the case.

In conclusion, the wisdom tooth is considered a vestigial organ in humans because it has lost its original function and often causes dental problems due to the evolution of smaller jaw sizes.