Nature’s leftovers: The vestigial organs that reveal our ancestry

Vestigial organs are anatomical structures that have lost all or most of their original evolutionary function. They represent remnants of organs that were functional in ancestral species but became reduced due to changes in habitat, lifestyle and natural selection. Their existence provides strong evidence for biological evolution, making them important for both UPSC Prelims and Mains.

In humans, common vestigial organs include the vermiform appendix, wisdom teeth, coccyx (tailbone), body hair and plica semilunaris (a remnant of the nictitating membrane). While some retain minor or secondary functions, such as the appendix supporting gut immunity, they are not essential for survival. Other vestigial features include goosebumps, which once helped ancestral species appear larger or conserve heat and muscles for moving the external ear, now largely non-functional.

In animals, classic examples include the hind limb bones in whales and snakes, wings of flightless birds (e.g., ostrich) and pelvic spurs in pythons. These structures illustrate evolutionary pathways, adaptation and functional regression.

In UPSC syllabus terms, vestigial organs connect to topics under genetics and evolution, human physiology and Darwinian theory. They also help explain concepts like adaptive radiation, natural selection and comparative anatomy, all of which strengthen evolutionary evidence.