Vestigial structures give
us evidence of organs or body parts that existed at one time and
eventually were not needed by the species to survive. For example, you
have an appendix but it's not an organ that is used very often, if at
all, by the body. However, in rabbits the appendix is a vital part of
their digestive system. Scientists think that the appendix helps to
digest large amounts of wild grasses and grains, which would have been a
useful organ to early humans while they were relying heavily on those
fibrous foods to sustain themselves. So vestigial structures basically give us an idea of something that a
species needed at one time in their past to survive but due to change
and evolution, they don't need it for survival anymore so it gradually
has started to disappear.
hope it helps
