TED-Ed: Why do humans have a third eyelid? | Dorsa Amir

The video explores vestigial structures in humans, such as the plica semilunaris, tailbone, palmaris longus muscle, and appendix. It explains how these structures, once useful to our ancestors, have persisted due to natural selection. While some vestigial traits remain because they are not harmful, others like the appendix can pose risks. The video highlights the imperfect nature of evolution and how it has shaped human anatomy over millions of years.

What role does the palmaris longus muscle play in human anatomy, and how can it be tested?

Why is the appendix considered a vestigial structure, and what are some theories about its persistence?