As organisms evolve, they carry along with them evidences of past ancestors. Many of these evidences are preserved because they are required for life. Thus our desert four-legged creatures retain much of the basic leg skeleton inherited from some early amphibian back in the Mesozoic era, over 200 million years ago. Other structures have become unnecessary as life styles have evolved. Many of these, of course, have been lost through time. Others, said to be vestigial, remain as remnants that have lost or greatly decreased their function, while other creatures have them fully operational.
Take the matter of ear muscles in humans, for example. Although in most
mammals these muscle allow large-scale movement of the ears to better locate sound,
human function appears to be limited to small boys attempting to impress small girls.
Perhaps the clearest examples are in animals living exclusively in the perpetual
darkness of caves, where useless eyes tend to be reduced to vestiges and even,
eventually, disappear. Vestiges aren't limited to structures, though; why some
people claim that good manners are rapidly becoming vestigial!
Listen to the Audio (mp3 format) as recorded by KTEP, Public Radio for the Southwest.
Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.
Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.