What do vestigial structures resemble?

Vestigial structures are remnants of organs or traits that had a function in an early ancestor but have since lost or changed their purpose through evolution. Because they reflect the anatomy of these presumed ancestors, they resemble structures that were functional in those earlier forms.

For example, the human appendix is often cited as a vestigial structure; while it may serve some minor roles today, it closely resembles the cecum found in herbivorous ancestors that had a crucial role in digesting cellulose.

This connection to ancestral traits highlights the evolutionary history of a species and provides important evidence for understanding how organisms have adapted over time. The resemblance to structures of presumed ancestors distinguishes vestigial structures from fully functional anatomical features, which is why this answer is the most accurate.