Even if a rudimentary organ actually has a function about which we observers are unaware why would it still provide excellent evidence in support of evolution by descent

Rudimentary (vestigial) organs in plant and animal are present in reduced form and do not perform any function in body but correspond to fully developed functional organs of related animals. Functions of rudimentary organs are still contradictory statement but they are believed to be remnants of organs which were complete and functional in their ancestors. Thus rudimentary organ provide a strong evidence for evolution by descent. Some examples of vestigial organs are; nictitating membrane in human, vestiges of hind limbs and pelvic girdles of pythons and pelvic girdles of pythons and greenland whales (which show that snakes and whales originally evolved from four footed ancestors)