A vestigial structure in humans is

1. Analyze the question The question asks which structure in humans is vestigial. A vestigial structure is a reduced or underdeveloped organ that has lost most or all of its original function over evolutionary time. It was useful in ancestors but is no longer needed.

2. Explain the concept Vestigial structures are evidence of evolution. Common human examples include:

• Coccyx (tail bone), the remnant of the tail that our ancestors had
• Appendix
• Wisdom teeth
• Nictitating membrane (the small fold at the inner corner of the eye)
• Muscles that move the ear

3. Evaluate each option

• A. Earlobe: This is part of the outer ear and is not vestigial. It is just a fleshy part of the ear, and its function is debated, but it is not a classic vestigial structure.
• B. Toe bone: Toe bones (phalanges) are fully functional. They help with balance and walking.
• C. Tail bone (coccyx): This is the remnant of the tail of our ancestors. It has no use as a tail in humans, though it still anchors some muscles. It is the classic vestigial structure.
• D. Spleen: This is a functional organ. It filters blood, destroys old red blood cells, and helps immunity.

4. Answer The correct option is C. tail bone.

5. Exam tip Remember the classic vestigial list with the phrase "CAW-N": Coccyx, Appendix, Wisdom teeth, Nictitating membrane. If you see any of these in a WASSCE, JAMB or NECO option list, it is most likely the answer.