A vestigial structure in humans is

Analyze the question: A vestigial structure is a body part that has lost most or all of its original function over the course of evolution. It was useful to ancestors but is now reduced or unnecessary.

Explain the concept: Vestigial structures are evidence of evolution. Examples in humans include:

• The appendix
• The tailbone (coccyx)
• Wisdom teeth
• Body hair (goosebumps)
• The muscles that move the ears

Check each option:

• A. Earlobe: This is just the fleshy lower part of the outer ear. It is not a vestigial structure in the usual sense, and it has no ancestral function that was lost.
• B. Gallbladder: This stores bile and is still functional. It is not vestigial.
• C. Tailbone (coccyx): This is the remnant of the tail our primate ancestors had. Humans no longer have an external tail, so the coccyx is a classic vestigial structure. (It still gives some muscle attachment support, but it has lost its original tail function.)
• D. Villus: Villi are finger-like projections in the small intestine that absorb digested food. They are very functional.

Answer: The tailbone is the vestigial structure, so the correct option is C.

Exam tip: Remember that "vestigial" means "a leftover trace." If a question asks for a vestigial organ in humans, think of the appendix, coccyx (tailbone), and wisdom teeth. If the options include an organ that clearly does an active job (like the gallbladder or villi), eliminate it.