The Countdown of Top Useless or Vestigial Organs

From LiveScience February 2005

The WiV\9s ov\ FlIghtless Bivds

In 1798, sixty years before Charles Darwin's first book was published, a French anatomist, E'ienne Geoffroy

St. Hilaire, traveled to Egypt with Napoleon where he witnessed and wrote about a flightless bird whose

"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

onlyJnown 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.

wings appeared useless for soaring. The bird that Hilaire described was an ostrich, but he described it as a

Biologists believe that for 100 million years the only vertebrates on Earth were water-dwelling 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.

1";'

EV'ectoV' Pili an.d Body HaiV'

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.

The Human. Tailbon.e (Coccyx)

Thes~8., 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.

HUMAN VESTIGIAL STRUCTURE

VOMERONASAL ORGAN EXTRINSIC EAR MUSCLES WISDOM TEETH A tiny piton e~h side of the septum is This trio of muscles most likely made it

Early humans had to chew a lot of lined with nonfunctioning possible for prehominids to move their ears plants to get enough calories to chemoreceptors. They may be all that independently of their heads, as rabbits and survive, making another row of remains ofaonce extensive dogs do. We still have them, which is why molars helpful. G1ly about 5 percent pheromone-detecting ability. most people can learn to wiggle their ears.

of the population has a healthy set of .-L--------------'-'_...___________J/(-t=============:=::============j----'these third molars. THIRD EYELID I- DARWIN'S POINT

L-------------i-l---t A common ancestor of birds and ....__________--, mammals may have had a A small folded point of skin toward~

the top of each ear is occasionallySUBCLAVI US MUSCLE membrane for protecting the eye found in modem humans. It may be

This small muscle stretching and sweeping out debris. Humans a remnant of a larger shape that under the shoulder from the retain only a tiny fold in the inner helped focus distant sounds. first rib to the collarbone comer of the eye.

;.:;~~:;::~~~~:;"' '~ -,"'K~.r·--I.• r---r<...,'! NECK RIB

~l:en~~~~~~a:~e~~~~~me ~/ ". . ; - ~ll '.". ~. ~O~::b~~~:;~~:~:~:m the.. " .. ..K' ~ 1'" /vL ' iI "" I "'-, ~ age of reptiles-still appear

~ in less than 1 percent ofthe

~-+,'d--.:::::..k--l~~~\:~.~~t_-_t--i'--:~~~"""'1--1 population. They oftenMALE NIPPLES Lactiferous ducts form well be fore testosterone causes sex differentiation in a fetus . Men have mammary tissue /~~~.~~' I\ \ :~~:~~~~~LEthat can be stimulated to produce milk. ~~~ ' .~.:ft Jit"~(1\..=:::1•.' . ' . :'~'~'}j ir~~lt~~g~I~:o: ~~s~~~u: isk·· ' .

I '\ missing in 11 percent of modem . >~=. \'\. ... ..... humans. I may once have been

II---"-~..~...-.+--.....-. .+--.--"r- -.-t}\ .; ' .; ••'. \ . ~" ~~~ob:~ ~~r~~~~i;~a~~st nfor~." .. ' .'. ..~;~' 1\ APPENDIX

This narrow, muscular tube ,. i..\ l...:'\ "reconstructive surgery. attached to the large intestine served as a special area to digest cellulose when the ~<;~:r: \ \~, '"\ ERECTOR P'Ll human diet consisted more of plant material than animal i

A!...\- - .1.....- - ..-i.--.-+-"--._.,i-j-'.........r.l'. ~...1'\ .. .......... :\ \ L' ~:~~,::::::::~,~:~;'.r"Pprotein. It also produces some white blood cells. Annually, more than 300,000 Americans have an appendectomy. ~\ ! J?j\U}\~ 1\ \ / ~~~~i;3~i~~:mp,

'----""-\+-,, ·- -·-+·..···--1--, r '~; II, r-V\\ 1\ f-.. ob,;o"",""mo;tof"'''m.

~"'- ~f1!~J,I(~~Lli. \ ,it\\....-,.I\/y/I \f\.--B-OD-YHAJ-R----,

A.iJ ~, I' ..- ~\~ ..... ! \ Brows help keep sweat from the ''''t<:J! .. . / \ \ l'\: r-~ \ eyes, and male facial hair may

PLANTARIS MUSCLE : '\ ~"-L ~2~'~~ r"~~ \ ' ~~~ya~;~;~t7ys:~~ ~~~~t:~; Often mistaken for a nerve by I I/

V I left on the human body serves

freshman medical students, the V \ no function. muscle was useful to olher I

primates for grasping with their feet. It has disappeared MALE UTERUS r-~""-----------, altogether in 9 percent of the A remnant of an undeveloped - THIRTEENTH RIB population. ) female reproductive organ Our closest cousins, chimpanzees

hangs off the male prostate and gorillas, have an extra set of gland. ribs. Most ofus have 12, but 8

percent of adults have the extras. FIFTH TOE

Lesser apes use all their toes for grasping or clinging to ­ FEMALE VAS DEFERNS - PYRAMIDALIS MUSCLE branches. Human need mainly What might become sperm ducts in More than 20 percent of us lack this the big toe for balance while males become the epoophoron in tiny, triangular pouch like muscle walking upright. females, a cluster of useless dead-end that attaches to the pubic bone. It

tubules near the ovaries may be a relic from pouched marsupials.

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