Figure 1. Vestigial pelvic bone in whale
VESTIGES OF THE PAST:
EVIDENCE OF EVOLUTION
Provided as evidence of evolution by Charles Darwin in "On the Origins of Species" (1859), vestigial organs are remainders of structures which where once useful, but subsequently became reduced or useless as they became unnecessary for survival.
Modern examples of vestigial organs exist in the pelvic bones of cetaceans (Figure 1) , reflecting their four-legged, terrestrial ancestry and in West African and West Indian Manatees which also bear evidence of a terrestrial origin through a marked similarity in their vestigial flipper nails (Figure 2) to nails found on the feet of extant elephants. (Edwards, 2012).
Vestigial Flipper Nail of West Indian Manatee
A particularly good example of vestigial organs are found in wings that still exist on flightless birds such as emus (Video). Although these rudimentary wings can serve in sexual display or for balance, they are useless for flight.
In a possible nod to their reptilian origin, vestigial claws are also found on particular species of birds (Fisher, 1940), especially when they are developing in the egg or in the nestling stage, which Fisher points to being a good indication of their vestigial nature.
In our own species, according to Brandon Miller of Live Science (2005), vestiges of previously useful organs or traits can be observed in the appendix, wisdom teeth, the coccyx (tailbone), erector pill (goose bumps) and some body hair.
Emus Dancing
REFERENCES
Edwards, C. (2012), Do Manatees have fingernails? Retrieved from:
www.savethemanatee.org/faq_fingernails.html
Fisher, H. (1940). The Occurrence of Vestigial Claws on the Wings of Birds
American Midland Naturalist. 23(1): 234-243 Retrieved from www.jstor.org/stable/2485270
Miller, B. (2005). Top 10 useless limbs (and other vestigial organs). Retrieved from www.livescience.com/11317-top-10-useless-limbs-vestigial-organs.html
VISUAL REFERENCES:
FIGURE 1: http://tedaltenberg.com/teacher/wms/science/unit3/10-evidence.shtml
FIGURE 2: Trichechus_manatus_ZoologicalGardenBerlin_Fritz Geller-Grimm
VIDEO: http://www.youtube.com/watch?v=2RVZvUJDTUE