When used with respect to animals (and other organisms), the term vestige refers to an under-developed and often no-longer-used body part that was present in fully developed and functional form in past generations. It refers to a remnant or trace of something that was once present and is possibly disappearing over successive generations. One example would be wings in ostriches—why would ostriches need wings if they do not possess the ability to fly?

The existence of vestigial characteristics is often used as a kind of evidence of evolution. A vestige has no function at present. Instead, it is a shadow of past adaptations and implies a continuous series of changes—it illustrates transition, the process of loosing a trait or part over time. And change through time is evolution. In the case of the ostrich, wings imply that the ostrich is derived from an ancestor that could fly.

Find out more: What is a Vestige?

Photo © Robert Airhart