The human body is a treasure trove of vestigial traits. A vestigial trait is a remnant of something we once had, but no longer need. Basically it is something that has been evolved away, but left a bit of itself behind. To those who cling to the outdated thought of creation, read on with an open mind. Evolution is as much a theory as gravity is at this point. Some of these evolutionary leftovers range from funny to deadly.
1) Plica Semilunaris
The small fold of tissue located on the inside corner of your eye (not the little bump in the very innermost corner, but the small flap right next to it). Your plica semilunari are the vestigial remnants of what are are most commonly found in birds, reptiles, and amphibians. Basically, the remnants of A THIRD EYELID!!! Apparently only one species of primate, the Calabar Angwantibo, is known to still have this third eyelid, referred to as "nictitating membranes". The membrane is typically translucent, and serves to moisten the eye, and clear debris. Just watch your cat blink very carefully, and you may see this neat structure in action!
2. Male Nipples
I really didn't think an image is required for this one. Male nipples, while ridiculous and serve no purpose, seem more aesthetically pleasing than anything else at this point. The biological function of male nipples is indeed a mystery. The story of male nipples begins, where all human life begins, in the womb. All fetuses begin life in the womb as females. In the absence of a fetal Y-chromosome, the embryo will develop into a full-blown female. When a Y-chromosome is present, however, the fetus will produce hormones like testosterone and develop into a male, but the nipples have already developed by this point, and just stick around. This essentially makes them like bulbs on a Christmas tree, fun to look and poke at.
These are the immune system's first line of defense, apparently, against ingested or inhaled foreign pathogens. However, the basic immunological roles of tonsils have yet to be understood. Simply put, the function may have once had must be no longer required, due to the frequency of them trying to kill their owner, and being removed.
4. The Ear
Well, not the ear itself, but a lot of the surrounding tissue and muscles. We have the muscles that most monkeys have to rotate and move the ears for better reception, but many of us can't even wiggle our ears. I can, and it's gloriously silly, but is it useful for more than a laugh from my kids? Not really. Also, in about 10% of the population, the outer rim of the ear called the helix can show signs of vestigial features. A thickening of the helix called "Darwin's tubercle" occurs at the juncture of the upper and middle thirds of the ear, a feature common to many mammals. I, personally, have this on one ear and not the other! The picture provided is indeed my ears, and, half vestigial trait it is! The feature is present in approximately 10.4% of the population, making me even more rare.
5. Arrector Pili
GOOSEBUMPS! No, not the books. Arrector Pili are the smooth muscle fibers that contract involuntarily to make your hair stand on end or make your skin bumpy. If you were a more furry creature this could make you warmer in the cold, or look larger to a predator. Clothing, fire, weapons, and the loss of hair (in comparison to our other primate cousins, not your pattern balding), have made this a vestigial trait as well. It serves no purpose in our own species, it has a function in our relatives (other primates), and did so in our ancestors.
It is also known as the "tailbone" for a reason. It's, pretty much, whats left from the days when we did have tails...and the unfortunate few that are still born with them. As a point of fact, most mammals have a tail at one point in their life, even if it is only during development in the womb. This includes humans as well. As I stated before, sometimes the tail sticks around even longer...
More vestigial traits listed here: http://en.wikipedia.org/wiki/Human_vestigiality
But if you Google it, so much more awaits: The Google Results
UPDATE (POST EDIT): http://www.independent.co.uk/news/world/europe/pope-francis-declares-evolution-and-big-bang-theory-are-right-and-god-isnt-a-magician-with-a-magic-wand-9822514.html
That's it for now. Stay tuned for more learning!
- The one, the ONLY, Holytotemic