A vestigial structure is a structure that kind-of just "hangs out" in our bodies. We don't really need it, yet it is there. So, why is it there??? We probably needed it, for example, when we needed to digest plants. (Appendix) Some say that the appendix was used for digesting plants and berries, but it is really just speculation. We "evolved" to not need the appendix.
Here are some other vestigial examples: wisdom teeth, tail bone, pelvic bone in a snake, and wings on a flightless bird.
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