List out all examples you can of a vestigial structure in humans.
1. Appendix: The appendix is a small, pouch-like structure located near the junction of the small and large intestines. It is believed to have played a role in digestion for our herbivorous ancestors, but it is now considered vestigial in humans as it no longer serves a significant function.
2. Wisdom teeth: Also known as third molars, wisdom teeth are the last set of molars to erupt in the human mouth. In many cases, there is not enough space for them to properly align with the other teeth, leading to impaction and other dental issues. This suggests that wisdom teeth are vestigial structures that were necessary for our ancestors who had larger jaws and ate a harder diet.
3. Coccyx (Tailbone): The coccyx is a small triangular bone at the base of the spine. It is thought to be the remnant of a tail that was present in our primate ancestors. Although the coccyx has lost its function in humans, it serves as an attachment point for ligaments and muscles.
4. Darwin's Tubercle: Darwin's tubercle refers to a small, raised cartilaginous bump on the edge of the human ear. It is believed to be a vestigial trait from our ancestors who had larger, more prominent ears that helped in sound localization.
5. Plica semilunaris: The plica semilunaris is a small fold of tissue located in the inner corner of the human eye. It is believed to be a remnant of a third eyelid known as the nictitating membrane, which is still functional in some animals for additional eye protection.
6. Male nipples: In males, nipples are vestigial structures as they do not serve any physiological purpose. They are believed to be remnants from embryonic development when the sexes have not yet differentiated.
7. Muscles for ear movement: Humans have small muscles in their ears that allow for minor movements, such as wiggling or lifting the ears slightly. These muscles were more developed and functional in our ancestors but have since lost their purpose in modern humans.
8. Erector pili muscles: These small muscles, responsible for goosebumps, attach to hair follicles in mammals. In humans, the erector pili muscles are vestigial as they no longer have a significant physiological function but can still contract involuntarily in response to certain stimuli.
9. Plantaris muscle: The plantaris muscle is a long, thin muscle located in the calf region of the leg. It is considered vestigial in humans as it has lost its primary function of providing extra strength for gripping and climbing, which is still present in other primates.