A thumbs-up or thumbs-down is a common hand gesture achieved by a closed fist held with the thumb extended upward or downward in approval or disapproval, respectively. These gestures have become metaphors in English: "The audience gave the movie the thumbs-up" means that the audience approved of the movie, regardless of whether the gesture was actually made.
The source of the gesture is obscure, but a number of origins have been proposed.
Carleton S. Coon, having observed Barbary apes in Gibraltar using the gesture, hypothesised in the anthropological classic The Story of Man that it is a mutual celebration of having opposable thumbs. Critics[who?] have suggested, however, that the apes may be simply imitating humans.
The Latin phrase pollice verso is used in the context of gladiatorial combat for a hand gesture used by Ancient Roman crowds to pass judgment on a defeated gladiator. However, the precise type of gesture described by the phrase pollice verso and its meaning are unclear in the historical and literary record.
In modern popular culture, it is assumed that "thumbs down" was the signal that a defeated gladiator should be condemned to death; "thumbs up", that he should be spared. The latter view was popularized by a widely reproduced painting by the 19th-century artist Jean-Léon Gérôme, whose Pollice Verso (usually known in English as "Thumbs Down") depicts a triumphant gladiator looking up into the stands for the verdict of the crowd.
Desmond Morris in Gestures: Their Origins and Distribution traces the practice back to a medieval custom used to seal business transactions. Over time, the mere sight of an upraised thumb came to symbolize harmony and kind feelings.[clarification needed] For an example in the 17th century see the Diego Velasquez painting The Lunch.
World War II
The gesture's popularization in America is generally attributed to the practices of World War II pilots, who used the thumbs up to communicate with ground crews prior to take-off. This custom may have originated with the China-based Flying Tigers, who were among the first American flyers involved in WWII. The appreciative Chinese would say ”挺好的“ ("ting hao de"), meaning "very good," and gesture with a thumbs up, which in Chinese means "you're number one." High officials in the Chinese government see it as a sign of respect. Any person from China will recognize this numerical gesture, and it can be seen in movies and photos of the era, though this has not been verified in print by American Volunteer Group (AVG) pilots.
During WWII, pilots on US aircraft carriers adopted the thumbs up gesture to alert the deck crew that they were ready to go and that the wheel chocks could be removed.
The use of the specific term "thumbs up" to describe the gesture can be found on a series of postcards produced by the Exhibit Supply Company of Chicago, Illinois during WWII. These cards were designed to be mailed to soldiers overseas.
The thumbs up signal has a generally positive connotation in English-speaking countries. However, its perceived meaning varies significantly from culture to culture.
In Afghanistan, Iran, and parts of Italy and Greece, the gesture is regarded as an obscene insult equivalent to what the middle finger signifies in most of Europe, especially when combined with a sweep of the arms. In these places, it roughly means "Sit on my phallus" and carries the same stigma as does raising the middle finger in the west. The sign has a similarly pejorative meaning in parts of West Africa, South America, Iran and Sardinia, according to Roger E. Axtell's book Gestures: The Do's and Taboos of Body Language Around the World." In southern Sardinia, where this gesture is noted for being particularly obscene, a hitchhiker would be well advised not to wave his thumb in the air expecting a car to pick him up, or he may find himself under the wheels of a large truck.   
Any extension of the thumb could potentially be offensive in Israel according to page 29 of Let's Go: Israel of the Let's Go Travel Guides series published in 2003 by St. Martin's Press. The book indicates that any extension of the thumb is offensive in Israel.
In Australia a thumb thrust upwards was used to gesture "up yours" prior to World War II. If the thumbs up is still or downwards, it usually means OK or alright (or agreement). Thumbs-up with a little upward motion can be a grave insult, depending on context. Australian Sign Language assigns this hand shape the meaning of "good".
In Germany, France, and Hungary it can simply indicate the number one, in the right context. However, the gesture generally holds a negative connotation despite regular usage of the thumbs up in western media.
In India the gesture is accepted. If the hand is wagged from side to side in a reverse-pendulum like movement while doing a thumbs up, it means "won't work" or "disagree". The thumbs up gesture is used on the logo for the Coca-Cola brand soda in India called Thumbs Up.
In the United States, American Sign Language users use the thumbs up wiggled modestly left and right to indicate the number ten (10). When held stationary and thrust toward another person the meaning is "yourself". When lifted up by the other palm, the meaning is "help".
On the internet, and most particularly at the Facebook social media site, the thumbs up gesture is shown as an icon and is associated with the term "like"—which within that context means to follow or subscribe to the page, posts, or profile of another individual or company.
More recently, these gestures are associated with movie reviews, having been popularized by critics Gene Siskel and Roger Ebert on their televised review show Siskel & Ebert — the thumb up meaning a positive opinion of a film; the thumb down meaning a negative one. The trademarked phrase "two thumbs up", originally meaning a positive review from both reviewers, has come to be used as an indication of very high quality or unanimity of praise.
By extension from the movie review usage, many websites allow users to approve or disapprove of items, such as comments in a forum, products in a store, or even other people's reviews of movies, books, products, etc., by choosing to click either a thumbs-up or thumbs-down button. In the aggregate, this serves as an evaluation system. Other users may then see the total number of thumbs up and thumbs down given to an item, or may simply see the number which is produced by subtracting thumbs down from thumbs up. (In the latter case, an item which has received exactly ten of each would read as having a rating of zero, rather than one of +10/-10.) Often, users may view a list of items in order of popularity, as ranked by this metric.
Hitchhikers in the West traditionally use a thumbs up gesture to solicit rides from oncoming vehicles, although in this presentation the arm is generally outstretched with the palm and closed fingers facing the motorist. The gesture is also usually performed with the hand nearest the motorist.
In scuba diving, the thumbs-up gesture is a specific diving signal given underwater, in which the diver indicates that he or she is about to stop his or her dive and ascend. This occasionally causes confusion in new divers, who might automatically gesture thumbs-up when trying to indicate approval — actually indicating a desire to stop diving and to ascend.
Unicode reserves 👍 or U+1F44D symbol and 👎 or U+1F44E symbol for the thumbs up and thumbs down gestures, respectively. Other symbols are -b (right hand) and d- (left hand).
|Wikimedia Commons has media related to Thumbs.|
- Carlton S. Coon: "The Story of Man" (1954)
- "James Grout: ''The Gladiator and the Thumb'', part of the Encyclopædia Romana". Penelope.uchicago.edu. Retrieved 2013-07-03.
- "Desmond Morris, Peter Collett, Peter Marsh and Marie O'Shaughnessy, 1979 Webified by Bernd Wechner: ''Gestures: Their Origin and Meanings, The Thumb Up''". Bernd.wechner.info. Retrieved 2013-07-03.
- "Did The Romans Turn Thumbs Down On Gladiators?". News.ku.edu. 1997-09-29. Retrieved 2013-07-03.
- Onion, Rebecca. "Slate: What Does a "Thumbs Up" Mean in Iraq?". Slate.msn.com. Retrieved 2013-07-03.
- Toledo, Roberto Pompeu de (March 14, 2007). "Uma paixão dos brasileiros". Veja Magazine (1999): 110
- Strazny, Philipp (2005). Encyclopedia of Linguistics: M-Z. Fitzroy Dearborn. p. 812. ISBN 1579584519.
- http://wiki.answers.com/Q/In_what_countries_is_it_offensive_to_make_the_thumbs-up_sign. Retrieved 1/9/2014. Missing or empty
- "Foreign Fingers". Retrieved 1/9/2014.
- Koerner, Brendan I. (March 28, 2003). "What Does a "Thumbs Up" Mean in Iraq?". Slate.
- "Ten". ASL Browser. Michigan State University Communication Technology Laboratory.
- "Yourself". ASL Browser. Michigan State University Communication Technology Laboratory.
- "Help". ASL Browser. Michigan State University Communication Technology Laboratory.