Top 10 Useless Limbs (and Other Vestigial Organs) Source: http://www.livescience.com/11317-­‐top-­‐10-­‐useless-­‐limbs-­‐vestigial-­‐organs.html The Human Appendix
In plant-eating vertebrates, the appendix is much larger and its main function is to help
digest a largely herbivorous diet. The human appendix is a small pouch attached to
the large intestine where it joins the small intestine and does not directly assist
digestion. Biologists believe it is a vestigial organ left behind from a plant-eating
ancestor. Interestingly, it has been noted by paleontologist Alfred Sherwood Romer in
his text The Vertebrate Body (1949) that the major importance of the appendix "would
appear to be financial support of the surgical profession", referring to, of course, the
large number of appendectomies performed annually. In 2000, in fact, there were
nearly 300,000 appendectomies performed in the United States, and 371 deaths from
appendicitis. Any secondary function that the appendix might perform certainly is not
missed in those who had it removed before it might have ruptured.
Wisdom Teeth in Humans
With all of the pain, time, and money that are put into dealing with wisdom teeth,
humans have become just a little more than tired of these remnants from their large
jawed ancestors. But regardless of how much they are despised, the wisdom teeth
remain, and force their way into mouths regardless of the pain inflicted. There are two
possible reasons why the wisdom teeth have become vestigial. The first is that the
human jaw has become smaller than its ancestors -and the wisdom teeth are trying to
grow into a jaw that is much too small. The second reason may have to do with
dental hygiene. A few thousand years ago, it might be common for an 18 year old
man to have lost several, probably most, of his teeth, and the incoming wisdom teeth
would prove useful. Now that humans brush their teeth twice a day, it's possible to
keep one's teeth for a lifetime. The drawback is that the wisdom teeth still want to
come in, and when they do, they usually need to be extracted to prevent any serious
pain.
The Blind Fish Astyanax Mexicanus
In an experiment designed by nature, the species of fish known as Astyanax mexicanus, dwelling
in caves deep underground off the coast of Mexico, cannot see. The pale fish has eyes, but as it is
developing in the egg, the eyes begin to degenerate, and the fish is born with a collapsed remnant
of an eye covered by flap of skin. These vestigial eyes probably formed after hundreds or even
thousands of years of living in total darkness. As for the experiment, a control is needed; and
luckily for us, fish of the same species live right above, near the surface, where there is plenty of
light, and these fish have fully functioning eyes. To test if the eyes of the blind mexicanus could
function if given the right environment, scientists removed the lens from the eye of the surfacedwelling fish and implanted it into the eye of the blind fish. It was observed that within eight days an
eye started to develop beneath the skin, and after two months the fish had developed a large
functioning eye with a pupil, cornea, and iris. The fish were blind, but now they see.
The Human Tailbone (Coccyx)
These fused vertebrae are the only vestiges that are left of the tail that other mammals
still use for balance, communication, and in some primates, as a prehensile limb. As our
ancestors were learning to walk upright, their tail became useless, and it slowly
disappeared. It has been suggested that the coccyx helps to anchor minor muscles and
may support pelvic organs. However, there have been many well documented medical
cases where the tailbone has been surgically removed with little or no adverse effects.
There have been documented cases of infants born with tails, an extended version of
the tailbone that is composed of extra vertebrae. There are no adverse health effects of
such a tail, unless perhaps the child was born in the Dark Ages. In that case, the child
and the mother, now considered witches, would've been killed instantly.
Erector Pili and Body Hair
The erector pili are smooth muscle fibers that give humans "goose bumps". If the erector pili are activated, the hairs that come out of
the nearby follicles stand up and give an animal a larger appearance that might scare off potential enemies and a coat that is thicker
and warmer. Humans, though, don't have thick furs like their ancestors did, and our strategy for several thousand years has been to
take the fur off other warm looking animals to stay warm. It's ironic actually that an animal, sensing danger is near, would puff up its
coat to look scarier, but the human hunter would see the puffier coat as a warm prize, leaving the thinner haired weaker looking animals
alone. Of course, some body hair is helpful to humans; eye brows can keep sweat out of the eyes and facial hair might influence a
woman's choice of sexual partner. All the rest of that hair, though, is essentially useless.
Hind Leg Bones in Whales
Biologists believe that for 100 million years the only vertebrates on Earth were waterdwelling creatures, with no arms or legs. At some point these "fish" began to develop
hips and legs and eventually were able to walk out of the water, giving the earth its
first land lovers. Once the land-dwelling creatures evolved, there were some
mammals that moved back into the water. Biologists estimate that this happened
about 50 million years ago, and that this mammal was the ancestor of the modern
whale. Despite the apparent uselessness, evolution left traces of hind legs behind,
and these vestigial limbs can still be seen in the modern whale. There are many
cases where whales have been found with rudimentary hind limbs in the wild, and
have been found in baleen whales, humpback whales, and in many specimens of
sperm whales. Most of these examples are of whales that had only leg bones, but
there were some that included feet with complete digits. It was reported recently that
whales and hippos were distantly related.
The Wings on Flightless Birds
In 1798, sixty years before Charles Darwin's first book was published, a French
anatomist, É´ienne Geoffroy St. Hilaire, traveled to Egypt with Napoleon where he
witnessed and wrote about a flightless bird whose wings appeared useless for
soaring. The bird that Hilaire described was an ostrich, but he described it as a
"cassowary", a term used back then to describe various birds of ostrich-like
appearance. Ostriches and cassowaries are among several birds that have wings
that are vestigial. Besides the cassowary, other flightless birds with vestigial wings
are the kiwi, and the kakapo (the only known flightless and nocturnal parrot), among
others. In general, wings of a bird are considered complex structures that are
specifically adapted for flight and those belonging to these flightless birds are no
different. They are, anatomically, rudimentary wings, but they could never give these
bulky birds flight. The wings are not completely useless, as they are used for balance
during running and in flagging down the honeys during courtship displays.