Quadrupedalism is a form of land animal locomotion
Terrestrial locomotion in animals
Terrestrial locomotion has evolved as animals adapted from aquatic to terrestrial environments. Locomotion on land raises different problems than that on water, with reduced friction being replaced by the effects of gravity....

 using four limbs
Limb (anatomy)
A limb is a jointed, or prehensile , appendage of the human or other animal body....

 or legs. An animal
Animals are a major group of multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and...

 or machine
A machine manages power to accomplish a task, examples include, a mechanical system, a computing system, an electronic system, and a molecular machine. In common usage, the meaning is that of a device having parts that perform or assist in performing any type of work...

 that usually moves in a quadrupedal manner is known as a quadruped, meaning "four feet" (from the Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

 quad for "four" and ped for "foot"). The majority of quadrupeds are vertebrate animals, including mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...

s such as cattle
Cattle are the most common type of large domesticated ungulates. They are a prominent modern member of the subfamily Bovinae, are the most widespread species of the genus Bos, and are most commonly classified collectively as Bos primigenius...

, dog
The domestic dog is a domesticated form of the gray wolf, a member of the Canidae family of the order Carnivora. The term is used for both feral and pet varieties. The dog may have been the first animal to be domesticated, and has been the most widely kept working, hunting, and companion animal in...

s and cat
The cat , also known as the domestic cat or housecat to distinguish it from other felids and felines, is a small, usually furry, domesticated, carnivorous mammal that is valued by humans for its companionship and for its ability to hunt vermin and household pests...

s, and reptile
Reptiles are members of a class of air-breathing, ectothermic vertebrates which are characterized by laying shelled eggs , and having skin covered in scales and/or scutes. They are tetrapods, either having four limbs or being descended from four-limbed ancestors...

s, like lizard
Lizards are a widespread group of squamate reptiles, with nearly 3800 species, ranging across all continents except Antarctica as well as most oceanic island chains...


Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...

s, human
Humans are the only living species in the Homo genus...

s, insect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...

s, crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...

s, and snake
Snakes are elongate, legless, carnivorous reptiles of the suborder Serpentes that can be distinguished from legless lizards by their lack of eyelids and external ears. Like all squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales...

s are not quadrupeds. However, there are some exceptions. For example, among the insects, the praying mantis is a quadruped. A few bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...

s may use quadrupedal movement in some circumstances, for example the shoebill
The Shoebill also known as Whalehead or Shoe-billed Stork, is a very large stork-like bird. It derives its name from its massive shoe-shaped bill. The adult bird is tall, long, across the wingspan and weighs . Their beaks have an average length of length of . The adult is mainly grey while the...

 will sometimes use its wings to right itself after lunging at prey.

Quadrupeds vs. tetrapods

Not all four-limbed animals are quadrupeds. Although arms and wings are, in the evolution
Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...

ary sense, modified legs, four-limbed vertebrates are in fact classed as tetrapod
Tetrapods are vertebrate animals having four limbs. Amphibians, reptiles, birds and mammals are all tetrapods; even snakes and other limbless reptiles and amphibians are tetrapods by descent. The earliest tetrapods evolved from the lobe-finned fishes in the Devonian...

s, members of the taxonomic
Linnaean taxonomy
Linnaean taxonomy can mean either of two related concepts:# the particular form of biological classification set up by Carl Linnaeus, as set forth in his Systema Naturæ and subsequent works...

 unit Tetrapoda. These include all vertebrate
Vertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...

s with quadrupedal ancestors, including mammals, reptiles, amphibians, and birds.

The distinction between quadrupeds and tetrapods is important in evolutionary biology, particularly in the context of biped
Bipedalism is a form of terrestrial locomotion where an organism moves by means of its two rear limbs, or legs. An animal or machine that usually moves in a bipedal manner is known as a biped , meaning "two feet"...

s, winged animals, and animals whose limbs have adapted to other roles (e.g. fin
A fin is a surface used for stability and/or to produce lift and thrust or to steer while traveling in water, air, or other fluid media, . The first use of the word was for the limbs of fish, but has been extended to include other animal limbs and man-made devices...

s, in the case of cetaceans and pinniped
Pinnipeds or fin-footed mammals are a widely distributed and diverse group of semiaquatic marine mammals comprising the families Odobenidae , Otariidae , and Phocidae .-Overview: Pinnipeds are typically sleek-bodied and barrel-shaped...

s). All of these animals are tetrapods, but none is a quadruped. Even snake
Snakes are elongate, legless, carnivorous reptiles of the suborder Serpentes that can be distinguished from legless lizards by their lack of eyelids and external ears. Like all squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales...

s, whose limbs have become vestigial
Vestigial structure
Vestigiality describes homologous characters of organisms that have seemingly lost all or most of their original function in a species through evolution. These may take various forms such as anatomical structures, behaviors and biochemical pathways. Some of these disappear early in embryonic...

 or lost entirely, are nevertheless tetrapods.

Quadrupedalism in humans

In July 2005, in rural Turkey
Turkey , known officially as the Republic of Turkey , is a Eurasian country located in Western Asia and in East Thrace in Southeastern Europe...

, scientists discovered five Kurd
Kürd or Kyurd or Kyurt may refer to:*Kürd Eldarbəyli, Azerbaijan*Kürd Mahrızlı, Azerbaijan*Kürd, Goychay, Azerbaijan*Kürd, Jalilabad, Azerbaijan*Kürd, Qabala, Azerbaijan*Qurdbayram, Azerbaijan...

ish siblings who had learned to walk naturally on their hands and feet. Unlike chimpanzee
Chimpanzee, sometimes colloquially chimp, is the common name for the two extant species of ape in the genus Pan. The Congo River forms the boundary between the native habitat of the two species:...

s, who ambulate on their knuckles
Knuckle-walking is a form of quadrupedal walking in which the forelimbs hold the fingers in a partially flexed posture that allows body weight to press down on the ground through the knuckles....

, the Turkish siblings
The Family That Walks On All Fours
The Family That Walks On All Fours is a BBC2 documentary that explored the science and the story of five individuals in the Ulas family in Turkey that walk with a previously unreported quadruped gait . The documentary was created by Passionate Productions and was broadcast on Friday 17 March 2006....

 (ranging from 18 to 34 years old) walked on their palms, allowing them to preserve the dexterity of their fingers. Another similar case has been reported in Chile, but the case is still being investigated and reports are not released as of March 2006.

The discovery of the family has provided scientists a unique view into human evolution
Human evolution
Human evolution refers to the evolutionary history of the genus Homo, including the emergence of Homo sapiens as a distinct species and as a unique category of hominids and mammals...

ary history. Nicholas Humphrey
Nicholas Humphrey
Professor Nicholas Keynes Humphrey is an English psychologist, based in Cambridge, who is known for his work on the evolution of human intelligence and consciousness. His interests are wide ranging...

 and John Skoyles
John Skoyles (scientist)
John Skoyles is a dyslexic neuroscientist and evolutionary psychologist. He initially studied philosophy of science at the London School of Economics and then did MRC funded research upon neuroscience and dyslexia at University College London....

 from the London School of Economics
London School of Economics
The London School of Economics and Political Science is a public research university specialised in the social sciences located in London, United Kingdom, and a constituent college of the federal University of London...

 and Roger Keynes from Cambridge University have suggested that their gait is due to two rare phenomena coming together. First, instead of initially crawling as infants on their knees, they started off learning to move around with a “bear crawl” on their feet. Second, due to their congenital brain impairment, they found balancing on two legs difficult. Because of this, their motor development was channelled into turning their bear crawl into a substitute for bipedality.

Other scientists, such as Stefan Mundlos of the Max Planck Institute, believe that the family's unusual gait may result from a genetic abnormality. Mundlos has found a region on chromosome 17
Chromosome 17 (human)
125px|rightChromosome 17 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 17 spans more than 81 million base pairs and represents between 2.5 and 3 % of the total DNA in cells.Identifying genes on each chromosome is an active area of...

 that might be responsible for human bipedalism.

Quadrupedal movement for exercise

Many people, especially practitioners of Parkour
Parkour is a method of movement focused on moving around obstacles with speed and efficiency. Originally developed in France, the main purpose of the discipline is to teach participants how to move through their environment by vaulting, rolling, running, climbing and jumping...

 and Freerunning and Georges Hébert's Natural Method, find benefit in using quadrupedal movement in order to build full body strength. For added difficulty this can be done faster or slower, or more exaggerated and to the effect of a push-up, or down stairs. Moving quadrupedally exercises the entire anterior: thighs, core, shoulders, and triceps.

Quadrupedal robots

BigDog is a dynamically stable quadruped robot created in 2005 by Boston Dynamics with Foster-Miller, the NASA Jet Propulsion Laboratory, and the Harvard University Concord Field Station. BigDog is long, stands tall, and weighs , about the size of a small mule. It is capable of traversing...

 is a dynamically stable quadruped
Quadrupedalism is a form of land animal locomotion using four limbs or legs. An animal or machine that usually moves in a quadrupedal manner is known as a quadruped, meaning "four feet"...

A robot is a mechanical or virtual intelligent agent that can perform tasks automatically or with guidance, typically by remote control. In practice a robot is usually an electro-mechanical machine that is guided by computer and electronic programming. Robots can be autonomous, semi-autonomous or...

 created in 2005 by Boston Dynamics
Boston Dynamics
Boston Dynamics is an engineering and robotics design company best known for the development of BigDog, a quadruped robot designed for the U.S. military with funding from DARPA, and DI-Guy, COTS software for realistic human simulation...

 with Foster-Miller
Foster-Miller, Inc., is a United States based military robotics manufacturer, a division of the United Kingdom's QinetiQ North America. Its two best-known products are TALON robots and LAST Armor....

, the NASA Jet Propulsion Laboratory
Jet Propulsion Laboratory
Jet Propulsion Laboratory is a federally funded research and development center and NASA field center located in the San Gabriel Valley area of Los Angeles County, California, United States. The facility is headquartered in the city of Pasadena on the border of La Cañada Flintridge and Pasadena...

, and the Harvard University Concord Field Station.

External links

  • Family may provide evolution clue - BBC News
    BBC News
    BBC News is the department of the British Broadcasting Corporation responsible for the gathering and broadcasting of news and current affairs. The department is the world's largest broadcast news organisation and generates about 120 hours of radio and television output each day, as well as online...

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.