Vestigial Structures in Humans
One of the most often cited evidences for human evolution is the existence of vestigial
structures. Vestigial structures are body parts that seemingly have no purpose or function.
Perhaps they once did, but somewhere along the way they lost their functions and are now
basically useless. Many other structures in the human body are thought to have once been
vestigial, but now they have a new function. The following are a few of the structures that
seem to be left over from an earlier version of humans and now have no necessary function.
appendix
The appendix is a world famous vestigial structure of the human body.
1. The Appendix
Olek Remesz
The appendix is a small projection off the side of the large intestine near the cecum. It looks
kind of like a tail and is found near where the small and large intestines meet. No one knows
the actual original function of the appendix, but Charles Darwin proposed it was once used by
primates to digest leaves. Now, the appendix in humans seems to be a depository of sorts for
bacteria that is used in the colon to aid in digestion and absorption. These bacteria, along with
others, may cause appendicitis and, if left untreated, can be fatal if the appendix ruptures and
the infections spreads.
By Heather Scoville, About.com Guide
2. The Tail Bone
Grays Anatomy of the Human Body, 20th ed
Attached to the bottom of the sacrum is the coccyx, or tail bone. This small, bony projection
seems to be a leftover structure of primate evolution. It is believed that human ancestors once
had tails and lived in trees. The coccyx would be where the tail was attached to the skeleton.
Since tails on humans have been selected against in nature, the coccyx is unnecessary in
modern day humans. Yet, it is still a part of the human skeleton.
3. The Plica Luminaris
C hamiltonkolb
Have you ever noticed that little flap of skin that covers the outside corner of your eyeball?
That's called the plica luminaris, and it is a vestigial structure. It doesn't really have a purpose,
but it is still there from our ancestors. It is believed to have once been part of a nictitating
membrane. Nictitating membranes are like third eyelids that move across the eye to protect it
or to moisten it as needed. Most animals have fully functioning nictitating membranes,
although the plica luminaris is now a vestigial structure in some mammals.
third eyelid
The third eyelid or “the plica semilunaris” is a transparent membrane used for the
protection of the eye and it is encountered most often at birds reptiles and fish, but some
mammals have it too. What you probably did not know is that humans have vestigial
third eyelids too. It is generally accepted that the small fold of tissue at the interior corner
of the eye, which you might have noticed many times before is a now useless remaining
of a transparent membrane we used to have in an early development stage.
http://10awesome.com/10-vestigial-structures-the-most-controversial-human-organs/4. The Arrector
Pili
Grays Anatomy of the Human Body, 20th ed.
When humans become cold, or sometimes scared, they get goose bumps. Goose bumps
are caused by the arrector pili muscle in the skin contracting and pulling the hair shaft
upwards. This whole process is vestigial for humans because we do not have enough hair
or fur to make it worthwhile. Fluffing up hair or fur creates pockets to trap air and warm
the body. It also can make the animal look bigger to threats that have scared them.
Humans still have the response of the arrector pili muscle pulling up the hair shaft, but
lack enough fur or hair for the response to actually work.
Ear Moving Muscles
The ear structure also shows evidence of a now useless ability. Most apes are capable of
moving the ears so that they may hear better hearing and become aware of dangers. For
humans, this ability became useless since long and the muscles responsible with moving
the ears atrophied and are now ineffective. Some people are still able to move their ears,
though. Can you?
http://www.sharecare.com/question/are-wisdom-teeth-vestigial-organs
The little toe
Here we are “attacking” one of the most controversial items on this list. Is the little toe
useful or useless? After reading and reading, I could not reach any conclusion on this one,
so you might want to clarify things for me if you can! Some people consider that the fifth
toe is absolutely vital for our balance, while others believe that it is only one of the
vestigial structures of our body, as it was used for climbing, swinging and grasping and it
does not affect balance either, so we will probably (and sadly) lose it at some point in the
future …
wisdom teeth
They are one of the most clearly vestigial structures of the human body. Sometimes, these
teeth do not manage to grow at all and continue to remain in the jawbone for the entire
life of the owner. They are clearly vestigial, as they are useless when eating. Humans
usually do not chew by using these teeth, because they are too far back in our mouths.
They are a mere prove that humans evolved from primates who owned much larger
mouths and were able to use those teeth.
Wisdom teeth are considered a vestigial organ -- no longer useful -- because our diet has
evolved. Early humans ate a mostly raw diet of foraged plants and hunted animals, which
required a lot of rough chewing. That wore down their teeth. By the time wisdom teeth,
the last molars, erupted between ages 17 and 25, their other molars and teeth had worn
down, allowing room for the wisdom tooth to come in. With the introduction of cooking,
our food got noticeably softer and our teeth remain in good shape. Also, modern
orthodonture helps us keep a well-rounded mouth structure. As a result, there often is not
enough room for wisdom teeth to erupt without damaging the other teeth, or else they
may become impacted when they start to erupt and need to be removed.
tonsils
For many years, tonsils were considered totally useless and were removed without any
second thought, if they got infected frequently. Today, however, we know that tonsils do
have a role, as they stop bacteria from reaching our organism, as part of our immune
system. This fact does not exclude them, though, from the list of vestigial organs of our
body, as creationists consider. As I mentioned above, their opponents define vestigial
structures as organs that lost their primary role, but may have kept however a secondary
or minor role in the organism, thus including tonsils as well.