Biped - AbsoluteAstronomy.com

Bipedalism is a form of terrestrial locomotion where an organism moves

Motion (physics)

In physics, motion is a change in position of an object with respect to time. Change in action is the result of an unbalanced force. Motion is typically described in terms of velocity, acceleration, displacement and time . An object's velocity cannot change unless it is acted upon by a force, as...

by means of its two rear limbs

Limb (anatomy)

A limb is a jointed, or prehensile , appendage of the human or other animal body....

, or legs. An animal

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

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 bipedal manner is known as a biped (icon), meaning "two feet" (from the Latin

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...

bi for "two" and ped for "foot"). Types of bipedal movement include walking

Walking

Walking is one of the main gaits of locomotion among legged animals, and is typically slower than running and other gaits. Walking is defined by an 'inverted pendulum' gait in which the body vaults over the stiff limb or limbs with each step...

, running

Running

Running is a means of terrestrial locomotion allowing humans and other animals to move rapidly on foot. It is simply defined in athletics terms as a gait in which at regular points during the running cycle both feet are off the ground...

, or hopping

Jumping

Jumping or leaping is a form of locomotion or movement in which an organism or non-living mechanical system propels itself through the air along a ballistic trajectory...

, on two appendage

Appendage

In invertebrate biology, an appendage is an external body part, or natural prolongation, that protrudes from an organism's body . It is a general term that covers any of the homologous body parts that may extend from a body segment...

s (typically legs).

Relatively few modern species are habitual bipeds whose normal method of locomotion is two-legged. Within mammal

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, habitual bipedalism has evolved six times, with the macropods, kangaroo mice

Kangaroo mouse

A kangaroo mouse is either one of the two species of jumping mouse native to the deserts of the Southwestern United States, predominantly found in the state of Nevada. Although native to the deserts in the southwest they have been plentiful in Missouri and Pennsylvania...

, dipodids

Dipodidae

The Dipodidae, or dipodids, are a family of rodents found across the northern hemisphere. This family includes over 50 species among the 16 genera....

, springhare

Springhare

The springhare , or springhaas, is not actually a hare, but a member of the order Rodentia. It is one of a number of species in the genus Pedetes, and is native to southern Africa. Synonyms are P. caffer or P...

, pangolin

Pangolin

A pangolin , also scaly anteater or Trenggiling, is a mammal of the order Pholidota. There is only one extant family and one genus of pangolins, comprising eight species. There are also a number of extinct taxa. Pangolins have large keratin scales covering their skin and are the only mammals with...

s and hominina

Hominina

The more anthropomorphic primates of the Hominini tribe are placed in the Hominina subtribe. Referred to as hominans, they are characterized by the evolution of an increasingly erect bipedal locomotion. The only extant species is Homo sapiens...

n apes. In the Triassic

Triassic

The Triassic is a geologic period and system that extends from about 250 to 200 Mya . As the first period of the Mesozoic Era, the Triassic follows the Permian and is followed by the Jurassic. Both the start and end of the Triassic are marked by major extinction events...

period some groups of archosaur

Archosaur

Archosaurs are a group of diapsid amniotes whose living representatives consist of modern birds and crocodilians. This group also includes all extinct non-avian dinosaurs, many extinct crocodilian relatives, and pterosaurs. Archosauria, the archosaur clade, is a crown group that includes the most...

s (a group that includes the ancestors of crocodile

Crocodile

A crocodile is any species belonging to the family Crocodylidae . The term can also be used more loosely to include all extant members of the order Crocodilia: i.e...

s) developed bipedalism; among their descendants the dinosaur

Dinosaur

Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...

s all the early forms and many later groups were habitual or exclusive bipeds; the bird

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 descended from one group of exclusively bipedal dinosaurs.

A larger number of modern species are capable of bipedal movement for a short time in exceptional circumstances. Several non-archosaurian lizard

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...

species move bipedally when running, usually to escape from threats. Many animals rear up on their hind legs whilst fighting or copulating. A few animals commonly stand on their hind legs, in order to reach food, to keep watch, to threaten a competitor or predator, or to pose in courtship, but do not move bipedally.

There are two main types of bipedal locomotion: macropods, some smaller birds, and heteromyid rodents

Heteromyidae

The family of rodents that include kangaroo rats, kangaroo mice and rock pocket mice is the Heteromyidae family. Most heteromyids live in complex burrows within the deserts and grasslands of western North America, though species within the Heteromys and Liomys genera are also found in forests and...

move by hopping on both legs simultaneously; other groups, including apes and larger birds, walk or run by moving one leg at a time.

Definition

The word is derived from the Latin

Latin

words bi(s) 'two (2)' and ped- 'foot', as contrasted with quadruped 'four feet'.

Facultative and obligate bipedalism

Zoologists often label behaviors, including bipedalism, as "facultative" (i.e. optional) or "obligate" (the animal has no reasonable alternative). Even this distinction is not completely clear-cut — for example, humans normally walk and run in biped fashion, but almost all can crawl on hands and knees when necessary. There are even reports of humans who normally walk on all fours with their feet but not their knees on the ground, but these cases are a result of conditions such as Uner Tan syndrome

Uner Tan syndrome

Uner Tan syndrome, Unertan syndrome or UTS is a syndrome proposed by the Turkish evolutionary biologist Uner Tan. Persons affected by this syndrome walk with a quadrupedal locomotion and are afflicted with primitive speech and severe mental retardation. Tan postulated that this is an example of...

— very rare genetic neurological disorders rather than normal behavior. Even if one ignores exceptions caused by some kind of injury or illness, there are many unclear cases, including the fact that "normal" humans can crawl on hands and knees. This article therefore avoids the terms "facultative" and "obligate", and focuses on the range of styles of locomotion normally used by various groups of animals.

Movement

There are a number of states of movement commonly associated with bipedalism.

Standing. Staying still on both legs. In most bipeds this is an active process, requiring constant adjustment of balance.
Walking
Walking
Walking is one of the main gaits of locomotion among legged animals, and is typically slower than running and other gaits. Walking is defined by an 'inverted pendulum' gait in which the body vaults over the stiff limb or limbs with each step...

. One foot in front of another, with at least one foot on the ground at any time.
Running
Running
Running is a means of terrestrial locomotion allowing humans and other animals to move rapidly on foot. It is simply defined in athletics terms as a gait in which at regular points during the running cycle both feet are off the ground...

. One foot in front of another, with periods where both feet are off the ground.
Jumping
Jumping
Jumping or leaping is a form of locomotion or movement in which an organism or non-living mechanical system propels itself through the air along a ballistic trajectory...

/Hopping
Hopping
Hopping may refer to:In activities:* Hopping, the act of jumping with one foot.* Freighthopping, the act of surreptitiously riding on a railroad freight car.* Island hopping, a series of journeys between islands....

. Moving by a series of jumps with both feet moving together.

Bipedal animals

The great majority of living terrestrial vertebrates are quadrupeds. Among mammals, bipedalism is a normal method of ground locomotion

Animal locomotion

Animal locomotion, which is the act of self-propulsion by an animal, has many manifestations, including running, swimming, jumping and flying. Animals move for a variety of reasons, such as to find food, a mate, or a suitable microhabitat, and to escape predators...

in various groups of primates (e.g. lemurs, gibbon

Gibbon

Gibbons are apes in the family Hylobatidae . The family is divided into four genera based on their diploid chromosome number: Hylobates , Hoolock , Nomascus , and Symphalangus . The extinct Bunopithecus sericus is a gibbon or gibbon-like ape which, until recently, was thought to be closely related...

s and Hominina

Hominina

), in the macropods (kangaroos, wallabies, etc.), and in a few groups of rodents, including kangaroo rat

Kangaroo rat

Kangaroo rats, genus Dipodomys, are small rodents native to North America. The common name derives from their bipedal form: as they hop in a manner similar to the much larger kangaroo, although they are not related...

s and kangaroo mice

Kangaroo mouse

in the family Heteromyidae

Heteromyidae

, as well as gerbils and spring hares. All birds are bipeds when on the ground, a feature inherited from their dinosaur

Dinosaur

ancestors. Bipedalism evolved more than once in archosaurs, the group that includes both dinosaurs and crocodilians. Many species of lizards become bipedal during high-speed, sprint locomotion, including the world's fastest lizard, the spiny-tailed iguana (genus Ctenosaura
Ctenosaura
Ctenosaura is a genus of lizard commonly known as spinytail iguanas. The genus is part of the large lizard family, Iguanidae and is native to Mexico and Central America. The species range in size from about 5 inches to well over one meter. The distinctive feature of this genus is presence of the...

). There are no known living or fossil bipedal amphibians.

Most bipedal animals move with their backs close to horizontal, using a long tail to balance the weight of their bodies. The primate version of bipedalism is unusual because the back is close to upright (completely upright in humans) and, among primates that move bipedally, only the lemurs have tails.

Humans and large birds walk

Walking

by raising one foot at a time. On the other hand most macropods, smaller birds and bipedal rodents move by hopping on both legs simultaneously. Tree kangaroos are able to utilize either form of locomotion, most commonly alternating feet when moving arboreally and hopping on both feet simultaneously when on the ground.

Archosaurs (include birds, crocodiles, and dinosaurs)

Birds are bipedal when not flying, with small birds tending to hop and larger birds walking with an alternating gait. All dinosaurs are believed to be descended from a fully bipedal ancestor, perhaps similar to Eoraptor
Eoraptor
Eoraptor was one of the world's earliest dinosaurs. It was a two-legged saurischian, close to the ancestry of theropods and sauropodomorphs. It lived ca. 231.4 million years ago, in what is now the northwestern region of Argentina...

. Bipedal movement also re-evolved in a number of other dinosaur

Dinosaur

lineages such as the iguanodon

Iguanodon

Iguanodon is a genus of ornithopod dinosaur that lived roughly halfway between the first of the swift bipedal hypsilophodontids and the ornithopods' culmination in the duck-billed dinosaurs...

s. Some extinct members of the crocodilian line, a sister group to the dinosaurs and birds, also evolved bipedal forms - a crocodile

Crocodile

A crocodile is any species belonging to the family Crocodylidae . The term can also be used more loosely to include all extant members of the order Crocodilia: i.e...

relative from the triassic

Triassic

, Effigia okeeffeae
Effigia okeeffeae
Effigia was an archosaur that lived in what is now New Mexico. The 2 meter fossil was collected by Edwin H. Colbert in blocks of rock from the Ghost Ranch Quarry, which were excavated in 1947 and 1948...

, is believed to be bipedal. Pterosaur

Pterosaur

Pterosaurs were flying reptiles of the clade or order Pterosauria. They existed from the late Triassic to the end of the Cretaceous Period . Pterosaurs are the earliest vertebrates known to have evolved powered flight...

s were previously thought to have been bipedal, but recent trackways have all shown quadrupedal locomotion.

Mammals

Bipedal movement is less common among mammal

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, most of which are quadruped

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"...

al. All primates possess some bipedal ability, though non-human primates primarily use quadrupedal locomotion on land. Primates aside, the largest mammalian group using exclusive bipedal movement are the macropods (kangaroos, wallabies and their relatives), which move via hopping. Other mammals also move via hopping, such as the kangaroo rat

Kangaroo rat

, springhare

Springhare

and certain primates such as the sifaka

Sifaka

Sifakas are a genus of lemur from the family Indriidae within the order Primates. Their name of the family is an onomatopoeia of their characteristic "shi-fak" alarm call. Like all lemurs, they are found only on the island of Madagascar...

and sportive lemur

Sportive lemur

The sportive lemurs are the medium sized primates that make up the Lepilemuridae family. The family consists of only one extant genus, Lepilemur, as well as the extinct genus Megaladapis. They are closely related to the other lemurs and exclusively live on the island of Madagascar...

. Very few mammals other than primates commonly move bipedally by an alternating gait rather than hopping. Exceptions are the ground pangolin and in some circumstances the tree kangaroo. http://blogs.scientificamerican.com/tetrapod-zoology/2011/10/17/tree-kangaroos-come-first/

Primates

Primates can be distinguished from other quadrupedal mammals as they exhibit a greater diversity in locomotor behaviors. These include arm swinging (brachiation), quadrumanous climbing, knuckle walking, and regular short bouts of bipedalism. In addition, quadrupedal locomotion in primates also exhibits significant differences from other mammals. These differences in gait characteristics are primarily adaptations to an arboreal environment.
All primates can sit upright. Many primates can stand upright on their hind legs without any support.
Chimpanzee

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, bonobo

Bonobo

The bonobo , Pan paniscus, previously called the pygmy chimpanzee and less often, the dwarf or gracile chimpanzee, is a great ape and one of the two species making up the genus Pan. The other species in genus Pan is Pan troglodytes, or the common chimpanzee...

s, gibbon

Gibbon

s and baboon

Baboon

Baboons are African and Arabian Old World monkeys belonging to the genus Papio, part of the subfamily Cercopithecinae. There are five species, which are some of the largest non-hominoid members of the primate order; only the mandrill and the drill are larger...

s exhibit relatively advanced forms of bipedalism. Injured chimpanzees and bonobos have been capable of sustained bipedalism.

Primates that live in tropical areas often wade through water in a bipedal stance. Gorillas, bonobos, proboscis monkey

Proboscis Monkey

The proboscis monkey or long-nosed monkey, known as the bekantan in Malay, is a reddish-brown arboreal Old World monkey that is endemic to the south-east Asian island of Borneo...

s and baboons have been observed wading bipedally. Three captive primates, one macaque Natasha

Natasha (monkey)

Natasha is a black macaque at the Safari Park zoo near Tel Aviv, Israel. She has become well known because, unlike other macaques who move by alternating between walking upright and on all four limbs, Natasha has walked upright all the time since suffering from a stomach flu that almost killed...

and two chimps, Oliver

Oliver (chimpanzee)

Oliver is a Common Chimpanzee and a former performing ape once promoted as a missing link or "Humanzee" due to his unusually human-like face and a tendency to walk upright...

and Poko (chimpanzee), were found to move bipedally. Natasha switched to exclusive bipedalism after an illness, while Poko was discovered in captivity in a tall, narrow cage. Oliver reverted to knuckle-walking

Knuckle-walking

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....

after developing arthritis.

In addition, non-human primates often use bipedal locomotion when carrying food. One hypothesis for human bipedalism is thus that it evolved as a result of differentially successful survival from carrying food to share with group members, although there are other hypotheses, as discussed below.

Limited bipedalism in mammals

Other mammals engage in limited, non-locomotory, bipedalism. A number of other animals, such as rat

Rat

Rats are various medium-sized, long-tailed rodents of the superfamily Muroidea. "True rats" are members of the genus Rattus, the most important of which to humans are the black rat, Rattus rattus, and the brown rat, Rattus norvegicus...

s, racoon

Racoon

Racoon is a Dutch rock band, formed in 1997. Their first big appearance was at the 1999 Noorderslagfestival. First album Till Monkeys Fly appeared in January 2000, produced by Michael Schoots . The first single, Feel Like Flying, became a hit and got a lot of airplay on the Dutch radiostation 3FM...

s, and beaver

Beaver

The beaver is a primarily nocturnal, large, semi-aquatic rodent. Castor includes two extant species, North American Beaver and Eurasian Beaver . Beavers are known for building dams, canals, and lodges . They are the second-largest rodent in the world...

s will squat on their hindlegs to manipulate some objects but revert to four limbs when moving (the beaver may also move bipedally if transporting wood for their dams). Bear

Bear

Bears are mammals of the family Ursidae. Bears are classified as caniforms, or doglike carnivorans, with the pinnipeds being their closest living relatives. Although there are only eight living species of bear, they are widespread, appearing in a wide variety of habitats throughout the Northern...

s will fight in a bipedal stance to use their forelegs as weapons. Ground squirrel

Ground squirrel

The ground squirrels are members of the squirrel family of rodents which generally live on or in the ground, rather than trees. The term is most often used for the medium-sized ground squirrels, as the larger ones are more commonly known as marmots or prairie dogs, while the smaller and less...

s and meerkat

Meerkat

The meerkat or suricate, Suricata suricatta, is a small mammal belonging to the mongoose family. Meerkats live in all parts of the Kalahari Desert in Botswana, in much of the Namib Desert in Namibia and southwestern Angola, and in South Africa. A group of meerkats is called a "mob", "gang" or "clan"...

s will stand on hind legs to survey their surroundings, but will not walk bipedally. Dog

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 can stand or move on two legs if trained, or if birth defect or injury precludes quadruped

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"...

alism. The gerenuk

Gerenuk

The Gerenuk , also known as the Waller's Gazelle, is a long-necked species of antelope found in dry bushy scrub and steppe in East Africa, from Somalia and eastern Ethiopia through northern and eastern Kenya to northeastern Tanzania...

antelope stands on its hind legs while eating from trees, as did the extinct giant ground sloth

Megatherium

Megatherium was a genus of elephant-sized ground sloths endemic to Central America and South America that lived from the Pliocene through Pleistocene existing approximately...

and chalicothere

Chalicothere

Chalicotheres were a group of herbivorous, odd-toed ungulate mammals spread throughout North America, Europe, Asia, and Africa during the Early Eocene to Early Pleistocene subepochs living from 55.8 mya—781,000 years ago, existing for approximately .They evolved around 40 million years ago from...

s. The spotted skunk

Spotted Skunk

The Eastern Spotted Skunk is smaller and more weasel-like than the striped skunk. The spotted skunks are faster and more agile than the striped skunks and they have better pelts. For the last 100 years, the Eastern Spotted Skunk was bred for its fine silky fur...

will also use limited bipedalism when threatened, rearing up on its forelimbs while facing the attacker so its anal glands

Anal glands

The anal glands or anal sacs are small glands found near the anus in many mammals, including dogs and cats. They are not found in humans or other primates. They are paired sacs located on either side of the anus between the external and internal sphincter muscles. Sebaceous glands within the...

, capable of spraying an offensive oil, face its attacker.

Limited bipedalism in non-mammals

Bipedalism is unknown among the amphibian

Amphibian

Amphibians , are a class of vertebrate animals including animals such as toads, frogs, caecilians, and salamanders. They are characterized as non-amniote ectothermic tetrapods...

s. Among the non-archosaur

Archosaur

reptile

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 bipedalism is rare, but it is found in the 'reared-up' running of lizard

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...

s such as agamids

Agamidae

Agamids, lizards of the family Agamidae, include more than 300 species in Africa, Asia, Australia, and a few in Southern Europe. Many species are commonly called dragons or dragon lizards. Phylogenetically they may be sister to the Iguanidae, and have a similar appearance. Agamids usually have...

and monitor lizard

Monitor lizard

Monitor lizards are usually large reptiles, although some can be as small as in length. They have long necks, powerful tails and claws, and well-developed limbs. Most species are terrestrial, but arboreal and semiaquatic monitors are also known...

s. Many reptile species will also temporarily adopt bipedalism while fighting. One genus of basilisk lizard

Basiliscus (genus)

Basiliscus is a genus of large corytophanid lizards, commonly known as basilisks, which are endemic to southern Mexico, Central America, and northern South America.-Taxonomy and etymology:...

can run bipedally across the surface of water for some distance. Among arthropod

Arthropod

An arthropod is an invertebrate animal having an exoskeleton , a segmented body, and jointed appendages. Arthropods are members of the phylum Arthropoda , and include the insects, arachnids, crustaceans, and others...

s, cockroach

Cockroach

Cockroaches are insects of the order Blattaria or Blattodea, of which about 30 species out of 4,500 total are associated with human habitations...

es are known to move bipedally at high speeds http://www.ingentaconnect.com/content/bsc/joa/2004/00000204/00000005/art00002?crawler=true. Bipedalism is virtually solely found in terrestrial animal

Terrestrial animal

Terrestrial animals are animals that live predominantly or entirely on land , as compared with aquatic animals, which live predominantly or entirely in the water , or amphibians, which rely on a combination of aquatic and terrestrial habitats...

s, though at least two types of octopus

Octopus

The octopus is a cephalopod mollusc of the order Octopoda. Octopuses have two eyes and four pairs of arms, and like other cephalopods they are bilaterally symmetric. An octopus has a hard beak, with its mouth at the center point of the arms...

walk bipedally on the sea floor using two of their arms, allowing the remaining arms to be used to camouflage the octopus as a mat of algae or a floating coconut.

Advantages

Limited and exclusive bipedalism can offer a species several advantages. Bipedalism raises the head; this allows a greater field of vision with improved detection of distant dangers or resources, access to deeper water for wading animals and allows the animals to reach higher food sources with their mouths. While upright, non-locomotory limb

Limb (anatomy)

A limb is a jointed, or prehensile , appendage of the human or other animal body....

s become free for other uses, including manipulation (in primates and rodents), flight (in birds), digging (in giant pangolin), combat (in bears and the large monitor lizard) or camouflage (in certain species of octopus). Running speeds can be increased when an animal lacks a flexible backbone, though the maximum bipedal speed appears less fast than the maximum speed of quadrupedal movement with a flexible backbone – the ostrich

Ostrich

The Ostrich is one or two species of large flightless birds native to Africa, the only living member of the genus Struthio. Some analyses indicate that the Somali Ostrich may be better considered a full species apart from the Common Ostrich, but most taxonomists consider it to be a...

reaches speeds of 65 km/h (40 mph) and the red kangaroo

Red Kangaroo

The Red Kangaroo is the largest of all kangaroos, the largest mammal native to Australia, and the largest surviving marsupial. It is found across mainland Australia, avoiding only the more fertile areas in the south, the east coast, and the northern rainforests.-Description:This species is a very...

70 km/h (43 mph), while the cheetah

Cheetah

The cheetah is a large-sized feline inhabiting most of Africa and parts of the Middle East. The cheetah is the only extant member of the genus Acinonyx, most notable for modifications in the species' paws...

can exceed 100 km/h (62 mph).

Bipedality in kangaroo rat

Kangaroo rat

s has been hypothesized to improve locomotor performance, which could aid in escaping from predators.

Evolution

Recent evidence regarding modern human sexual dimorphism

Sexual dimorphism

Sexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...

(physical differences between men and women) in the lumbar spine has been seen in pre-modern primates such as Australopithecus africanus
Australopithecus africanus
Australopithecus africanus was an early hominid, an australopithecine, who lived between 2–3 million years ago in the Pliocene. In common with the older Australopithecus afarensis, A. africanus was slenderly built, or gracile, and was thought to have been a direct ancestor of modern humans. Fossil...

. This dimorphism has been seen as an evolutionary adaptation of females to bear lumbar load better during pregnancy

Pregnancy

Pregnancy refers to the fertilization and development of one or more offspring, known as a fetus or embryo, in a woman's uterus. In a pregnancy, there can be multiple gestations, as in the case of twins or triplets...

, an adaptation that non-bipedal primates would not need to make.

Bipedalism has a number of adaptive advantages, and has evolved independently in a number of lineages.

Early reptiles and lizards

The first known biped is the bolosaurid

Bolosaurid

Bolosaurids are an extinct family of anapsid reptiles from the Permian Period. Fossils have been found in North America, Russia and Germany. The bolosaurids were unusual for their time period by being bipedal, the oldest known tetrapods to have been so. Their teeth suggest that they were...

Eudibamus
Eudibamus
Eudibamus is an extinct genus of biped bolosaurid from the early Permian some 290 million years ago of Germany. Eudibamus is claimed to be the first bipedal vertebrate....

whose fossils date from 290 million years ago. Its long hindlegs, short forelegs, and distinctive joints all suggest bipedalism. This may have given increased speed. The species was extinct before the dinosaurs appeared.

Independent of Eudibamus, some modern lizard species have developed the capacity to run on their hind legs for added speed.

Dinosaurs and birds

Bipedalism also evolved independently among the dinosaurs. Dinosaurs diverged from their archosaur

Archosaur

ancestors approximately 230 million years ago during the Middle to Late Triassic

Triassic

period, roughly 20 million years after the Permian-Triassic extinction event

Permian-Triassic extinction event

The Permian–Triassic extinction event, informally known as the Great Dying, was an extinction event that occurred 252.28 Ma ago, forming the boundary between the Permian and Triassic geologic periods, as well as the Paleozoic and Mesozoic eras...

wiped out an estimated 95% of all [life on Earth]. Radiometric dating

Radiometric dating

Radiometric dating is a technique used to date materials such as rocks, usually based on a comparison between the observed abundance of a naturally occurring radioactive isotope and its decay products, using known decay rates...

of fossils from the early dinosaur genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

Eoraptor
Eoraptor
Eoraptor was one of the world's earliest dinosaurs. It was a two-legged saurischian, close to the ancestry of theropods and sauropodomorphs. It lived ca. 231.4 million years ago, in what is now the northwestern region of Argentina...

establishes its presence in the fossil record at this time. Paleontologists believe Eoraptor resembles the common ancestor

Common descent

In evolutionary biology, a group of organisms share common descent if they have a common ancestor. There is strong quantitative support for the theory that all living organisms on Earth are descended from a common ancestor....

of all dinosaurs; if this is true, its traits suggest that the first dinosaurs were small, bipedal predators. The discovery of primitive, dinosaur-like ornithodirans such as Marasuchus
Marasuchus
Marasuchus is a genus of dinosaur-like ornithodiran from the middle Triassic Chañares Formation of Argentina. The species Marasuchus lilloensis was originally described as a second species of Lagosuchus, L. lilloensis...

and Lagerpeton
Lagerpeton
Lagerpeton is a genus of basal dinosauromorph from the Ladinian . Lagerpeton is known from several specimens of hindlimbs, hips, vertebrae, and feet. It was about 0.7 metres long and was found in the Chañares Formation of Argentina. It has unique feet, with an unusually long fourth toe...

in Argentinian

Argentina

Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...

Middle Triassic

In the geologic timescale, the Middle Triassic is the second of three epochs of the Triassic period or the middle of three series in which the Triassic system is divided. It spans the time between 245 ± 1.5 Ma and 228 ± 2 Ma...

strata supports this view; analysis of recovered fossils suggests that these animals were indeed small, bipedal predators.

Mammals

A number of mammals will adopt a bipedal stance in specific situations such as for feeding or fighting. A number of groups of extant mammals have independently evolved bipedalism as their main form of locomotion - for example humans, giant pangolin

Giant Pangolin

The Giant Pangolin is a pangolin species. Members of the species inhabit Africa with a range stretching along the equator from west Africa to Uganda. The Giant Pangolin is the largest species of pangolin, or "scaly anteaters" – the large, scaled mammals belonging to the Manidae family. It...

s, the extinct giant ground sloths

Megatheriidae

Megatheriidae is a family of extinct ground sloths that lived from approximately 23 mya—11,000 years ago, existing for approximately .Megatheriids appeared later in the Oligocene, some 30 million years ago, also in South America. The group includes the heavily-built Megatherium and Eremotherium...

, numerous species of jumping rodent

Rodent

Rodentia is an order of mammals also known as rodents, characterised by two continuously growing incisors in the upper and lower jaws which must be kept short by gnawing....

s and macropods. Humans, as their bipedalism has been extensively studied are documented in the next section. Macropods are believed to have evolved bipedal hopping only once in their evolution, at some time no later than 45 million years ago.

Humans

There are at least twelve distinct hypotheses as to how and why bipedalism evolved in humans, and also some debate as to when. Bipedalism evolved well before the large human brain or the development of stone tools. Bipedal specializations are found in Australopithecus
Australopithecus
Australopithecus is a genus of hominids that is now extinct. From the evidence gathered by palaeontologists and archaeologists, it appears that the Australopithecus genus evolved in eastern Africa around 4 million years ago before spreading throughout the continent and eventually becoming extinct...

fossils from 4.2-3.9 million years ago The different hypotheses are not necessarily mutually exclusive and a number of selective forces may have acted together to lead to human bipedalism. It is important to distinguish between adaptations for bipedalism and adaptations for running, which came later still.

Possible reasons for the evolution of human bipedalism include freeing the hands for tool use and carrying, sexual dimorphism

Sexual dimorphism

in food gathering, changes in climate and habitat (from jungle

Jungle

A Jungle is an area of land in the tropics overgrown with dense vegetation.The word jungle originates from the Sanskrit word jangala which referred to uncultivated land. Although the Sanskrit word refers to "dry land", it has been suggested that an Anglo-Indian interpretation led to its...

to savanna

Savanna

A savanna, or savannah, is a grassland ecosystem characterized by the trees being sufficiently small or widely spaced so that the canopy does not close. The open canopy allows sufficient light to reach the ground to support an unbroken herbaceous layer consisting primarily of C4 grasses.Some...

) and to reduce the amount of skin exposed to the tropical sun.

Traveling efficiency hypothesis

An alternative explanation is the mixture of savanna and scattered forests increased terrestrial travel by proto-humans between clusters of trees, and bipedalism offered greater efficiency for long-distance travel between these clusters than quadrupedalism.

Postural feeding hypothesis

The postural feeding hypothesis has been recently supported by Dr. Kevin Hunt, a professor at Indiana University. This hypothesis asserts that chimpanzees were only bipedal when they ate. While on the ground, they would reach up for fruit hanging from small trees and while in trees, bipedalism was utilized by grabbing for an overhead branch. These bipedal movements may have evolved into regular habits because they were so convenient in obtaining food. Also, Hunt hypothesises that these movements coevolved with chimpanzee

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:...

arm-hanging, as this movement was very effective and efficient in harvesting food. When analyzing fossil anatomy, Australopithecus afarensis
Australopithecus afarensis
Australopithecus afarensis is an extinct hominid that lived between 3.9 and 2.9 million years ago. A. afarensis was slenderly built, like the younger Australopithecus africanus. It is thought that A...

has very similar features of the hand and shoulder to the chimpanzee, which indicates hanging arms. Also, the Australopithecus
Australopithecus
Australopithecus is a genus of hominids that is now extinct. From the evidence gathered by palaeontologists and archaeologists, it appears that the Australopithecus genus evolved in eastern Africa around 4 million years ago before spreading throughout the continent and eventually becoming extinct...

hip and hind limb very clearly indicate bipedalism, but these fossils also indicate very inefficient locomotive movement when compared to humans. For this reason, Hunt argues that bipedalism evolved more as a terrestrial feeding posture than as a walking posture. As Hunt says, “A bipedal postural feeding adaptation may have been a preadaptation

Preadaptation

In evolutionary biology, preadaptation describes a situation where a species evolves to use a preexisting structure or trait inherited from an ancestor for a potentially unrelated function...

for the fully realized locomotor bipedalism apparent in Homo erectus

Homo erectus

Homo erectus is an extinct species of hominid that lived from the end of the Pliocene epoch to the later Pleistocene, about . The species originated in Africa and spread as far as India, China and Java. There is still disagreement on the subject of the classification, ancestry, and progeny of H...

.”

Provisioning model

One theory on the origin of bipedalism is the behavioral model presented by C. Owen Lovejoy

Owen Lovejoy (anthropologist)

Claude Owen Lovejoy is a functional anatomist at Kent State University, Ohio and Director of the Matthew Ferrini Institute for Human Evolutionary Research. He is best known for his work on Australopithecine locomotion and the origins of bipedalism...

, known as "male provisioning". Lovejoy theorizes that the evolution

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...

of bipedalism was linked to monogamy. In the face of long inter-birth intervals and low reproductive rates typical of the apes, early hominids engaged in pair-bonding that enabled greater parental effort directed towards rearing offspring. Lovejoy proposes that male provisioning of food would improve the offspring survivorship and increase the pair's reproductive rate. Thus the male would leave his mate and offspring to search for food and return carrying the food in his arms walking on his legs. This model is supported by the reduction ("feminization") of the male canine teeth in early hominids such as Sahelanthropus tchadensis
Sahelanthropus tchadensis
Sahelanthropus tchadensis is an extinct hominid species that is dated to about . Whether it can be regarded as part of the Hominina tree is unclear; there are arguments both supporting and rejecting it...

and Ardipithecus ramidus, which along with low body size dimorphism in Ardipithecus and Australopithecus, suggests a reduction in inter-male antagonistic behavior in early hominids. In addition, this model is supported by a number of modern human traits associated with concealed ovulation (permanently enlarged breasts, lack of sexual swelling) and low sperm competition (moderate sized testes, low sperm mid-piece volume) that argues against recent adaptation to a polygynous reproductive system.

However, this model has generated some controversy, as others have argued that early bipedal hominids were instead polygynous. Among most monogamous primates, males and females are about the same size. That is sexual dimorphism

Sexual dimorphism

is minimal, and other studies have suggested that Australopithecus afarensis

Australopithecus afarensis

Australopithecus afarensis is an extinct hominid that lived between 3.9 and 2.9 million years ago. A. afarensis was slenderly built, like the younger Australopithecus africanus. It is thought that A...

males were nearly twice the weight of females (as well as a great deal taller). However, Lovejoy's model posits that the larger range a provisioning male would have to cover (to avoid competing with the female for resources she could attain herself) would select for increased male body size to limit predation risk. Furthermore, as the species became more bipedal, specialized feet would prevent the infant from conveniently clinging to the mother - hampering the mother's freedom and thus make her and her offspring more dependent on resources collected by others. Modern monogamous primates such as gibbons

Gibbons

Notable people named Gibbons include:* Alan Gibbons, a British author* Beth Gibbons , a British singer* Billy Gibbons, a guitarist for ZZ Top* Carroll Gibbons , an American-born British bandleader...

tend to be also territorial, but fossil evidence indicates that Australopithecus afarensis lived in large groups. However, while both gibbons and hominids have reduced canine sexual dimorphism, female gibbons enlarge ('masculinize') their canines so they can actively share in the defense of their home territory. Instead, the reduction of the male hominid canine is consistent with reduced inter-male aggression in a group living primate.

Early bipedalism in homininae model

Recent studies of 4.4 million years old Ardipithecus ramidus suggest bipedalism, it is thus possible that bipedalism evolved very early in homininae

Homininae

Homininae is a subfamily of Hominidae, which includes humans, gorillas and chimpanzees, and some extinct relatives; it comprises all those hominids, such as Australopithecus, that arose after the split from orangutans . Our family tree, which has 3 main branches leading to chimpanzees, humans and...

and was reduced in chimpanzee and gorilla when they became more specialized. According to Richard Dawkins in his book "The Ancestor's Tale

The Ancestor's Tale

The Ancestor's Tale is a 2004 popular science book by Richard Dawkins, with contributions from Dawkins' research assistant Yan Wong. It follows the path of humans backwards through evolutionary history, meeting humanity's cousins as they converge on common ancestors...

", chimps and bonobos are descended from Australopithecus

Australopithecus

Australopithecus is a genus of hominids that is now extinct. From the evidence gathered by palaeontologists and archaeologists, it appears that the Australopithecus genus evolved in eastern Africa around 4 million years ago before spreading throughout the continent and eventually becoming extinct...

gracile type species while gorillas are descended from Paranthropus

Paranthropus

The robust australopithecines, members of the extinct hominin genus Paranthropus , were bipedal hominids that probably descended from the gracile australopithecine hominids...

. These apes may have once been bipedal, but then lost this ability when they were forced back into an arboreal habitat, presumably by those australopithecines who eventually became us (see Homininae

Homininae

). Early homininae

Homininae

s such as Ardipithecus ramidus may have possessed an arboreal type of bipedalism that later independently evolved towards knuckle-walking in chimpanzees and gorillas and towards efficient walking and running in modern humans (see figure). It is also proposed that one cause of Neanderthal extinction was a less efficient running.

Warning display (Aposematic) model

Joseph Jordania

Joseph Jordania is an Australian-Georgian ethnomusicologist and evolutionary musicologist. In some early publications his name was spelled as Zhordania...

from the University of Melbourne recently (2011) suggested that bipedalism was one of the central element of the general defense strategy of early hominids, based on aposematism

Aposematism

Aposematism , perhaps most commonly known in the context of warning colouration, describes a family of antipredator adaptations where a warning signal is associated with the unprofitability of a prey item to potential predators...

, or warning display and intimidation

Intimidation

Intimidation is intentional behavior "which would cause a person of ordinary sensibilities" fear of injury or harm. It's not necessary to prove that the behavior was so violent as to cause terror or that the victim was actually frightened.Criminal threatening is the crime of intentionally or...

of potential predators and competitors with exaggerated visual and audio signals. According to this model, hominids were trying to stay as visible and as loud as possible all the time. Several morphological and behavioral developments were employed to achieve this goal: upright bipedal posture, longer legs, long tightly coiled hair on the top of the head, body painting

Body painting

Body painting, or sometimes bodypainting, is a form of body art. Unlike tattoo and other forms of body art, body painting is temporary, painted onto the human skin, and lasts for only several hours, or at most a couple of weeks. Body painting that is limited to the face is known as face painting...

, threatening synchronous body movements, loud voice and extremely loud rhythmic singing/stomping/drumming on external subjects. Slow locomotion and strong body odor (both characteristic for hominids and humans) are other features often employed by aposematic species to advertise their non-profitability for potential predators.

Other behavioural models

There are a variety of ideas which promote a specific change in behaviour as the key driver for the evolution of hominid bipedalism. For example, Wescott (1967) and later Jablonski & Chaplin (1993) suggest that bipedal threat displays could have been the transitional behaviour which led to some groups of apes beginning to adopt bipedal postures more often. Others (e.g. Dart 1925) have offered the idea that the need for more vigilance against predators could have provided the initial motivation. Dawkins (e.g. 2004) has argued that it could have begun as a kind of fashion that just caught on and then escalated through sexual selection. And it has even been suggested (e.g. Tanner 1981:165) that male phallic display could have been the initial incentive.

Thermoregulatory model

The thermoregulatory model explaining the origin of bipedalism is one of the simplest theories so far advanced, but it is a viable explanation. Dr. Peter Wheeler, a professor of evolutionary biology, proposes that bipedalism raises the amount of body surface area higher above the ground which results in a reduction in heat gain and helps heat dissipation. When a hominid is higher above the ground, the organism accesses more favorable wind speeds and temperatures. During heat seasons, greater wind flow results in a higher heat loss, which makes the organism more comfortable. Also, Wheeler explains that a vertical posture minimizes the direct exposure to the sun whereas quadrupedalism exposes more of the body to direct exposure. Analysis and interpretations of Ardipithecus

Ardipithecus

Ardipithecus is a very early hominin genus. Two species are described in the literature: A. ramidus, which lived about 4.4 million years ago during the early Pliocene, and A. kadabba, dated to approximately 5.6 million years ago ....

reveal that this hypothesis needs modification to consider that the forest

Forest

A forest, also referred to as a wood or the woods, is an area with a high density of trees. As with cities, depending where you are in the world, what is considered a forest may vary significantly in size and have various classification according to how and what of the forest is composed...

and woodland

Woodland

Ecologically, a woodland is a low-density forest forming open habitats with plenty of sunlight and limited shade. Woodlands may support an understory of shrubs and herbaceous plants including grasses. Woodland may form a transition to shrubland under drier conditions or during early stages of...

environmental preadaptation

Preadaptation

In evolutionary biology, preadaptation describes a situation where a species evolves to use a preexisting structure or trait inherited from an ancestor for a potentially unrelated function...

of early-stage hominid bipedalism preceded further refinement of bipedalism by the pressure of natural selection

Natural selection

Natural selection is the nonrandom process by which biologic traits become either more or less common in a population as a function of differential reproduction of their bearers. It is a key mechanism of evolution....

. This then allowed for the more efficient exploitation of the hotter conditions ecological niche

Ecological niche

In ecology, a niche is a term describing the relational position of a species or population in its ecosystem to each other; e.g. a dolphin could potentially be in another ecological niche from one that travels in a different pod if the members of these pods utilize significantly different food...

, rather than the hotter conditions being hypothetically bipedalism's initial stimulus.

Carrying models

Charles Darwin wrote that "Man could not have attained his present dominant position in the world without the use of his hands, which are so admirably adapted to the act of obedience of his will" Darwin (1871:52) and many models on bipedal origins are based on this line of thought. Gordon Hewes (1961) suggested that the carrying of meat "over considerable distances" (Hewes 1961:689) was the key factor. Isaac (1978) and Sinclair et al. (1986) offered modifications of this idea as indeed did Lovejoy (1981) with his 'provisioning model' described above. Others, such as Nancy Tanner (1981) have suggested that infant carrying was key, whilst others have suggested stone tools and weapons drove the change.

Wading models

Several theories have been proposed regarding the influence of water on human bipedalism. The aquatic ape hypothesis

Aquatic ape hypothesis

The aquatic ape hypothesis is an alternative explanation of some characteristics of human evolution which hypothesizes that the common ancestors of modern humans spent a period of time adapting to life in a partially aquatic environment. The hypothesis is based on differences between humans and...

, promoted for several decades by Elaine Morgan

Elaine Morgan (writer)

Elaine Morgan OBE is a Welsh writer for television and also the author of several books on evolutionary anthropology, especially the aquatic ape hypothesis: The Descent of Woman, The Aquatic Ape, The Scars of Evolution, The Descent of the Child, The Aquatic Ape Hypothesis, and The Naked Darwinist...

, proposed that swimming, diving and aquatic food sources exerted a strong influence on many aspects of human evolution, including bipedalism. It is not accepted by or considered a serious theory within anthropological scholarly community.

Other scholarly theories have been proposed that suggest wading and the exploitation of aquatic food sources (providing essential nutrients for human brain evolution or critical fallback foods) may have exerted evolutionary pressures on human ancestors leading to bipedalism.

Physiology

Bipedal movement occurs in a number of ways, and requires many mechanical and neurological adaptations. Some of these are described below.

Standing

Energy-efficient means of standing bipedally involve constant adjustment of balance, and of course these must avoid overcorrection

Feedback

Feedback describes the situation when output from an event or phenomenon in the past will influence an occurrence or occurrences of the same Feedback describes the situation when output from (or information about the result of) an event or phenomenon in the past will influence an occurrence or...

. The difficulties associated with simple standing in upright humans are highlighted by the greatly increased risk of falling present in the elderly, even with minimal reductions in control system effectiveness.

Walking

Walking is characterized by an "inverted pendulum" movement in which the body vaults over a stiff leg with each step. Force plates can be used to quantify the whole-body kinetic & potential energy, with walking displaying an out-of-phase relationship indicating exchange between the two. Interestingly, this model applies to all walking organisms regardless of the number of legs, and thus bipedal locomotion does not differ in terms of whole-body kinetics.

In humans, walking is composed of several separate processes:

Vaulting over a stiff stance leg
Passive ballistic movement of the swing leg
A short 'push' from the ankle prior to toe-off, propelling the swing leg
Rotation of the hips about the axis of the spine, to increase stride length
Rotation of the hips about the horizontal axis to improve balance during stance

Running

Running is characterized by a spring-mass movement. Kinetic and potential energy are in phase, and the energy is stored & released from a spring-like limb during foot contact. Again, the whole-body kinetics are similar to animals with more limbs.

Musculature

Bipedalism requires strong leg muscles, particularly in the thighs. Contrast in domesticated

Domestication

Domestication or taming is the process whereby a population of animals or plants, through a process of selection, becomes accustomed to human provision and control. In the Convention on Biological Diversity a domesticated species is defined as a 'species in which the evolutionary process has been...

poultry

Poultry

Poultry are domesticated birds kept by humans for the purpose of producing eggs, meat, and/or feathers. These most typically are members of the superorder Galloanserae , especially the order Galliformes and the family Anatidae , commonly known as "waterfowl"...

the well muscled legs, against the small and bony wings. Likewise in humans, the quadriceps and hamstring

Hamstring

In human anatomy, the hamstring refers to any one of the three posterior thigh muscles, or to the tendons that make up the borders of the space behind the knee. In modern anatomical contexts, however, they usually refer to the posterior thigh muscles, or the tendons of the semitendinosus, the...

muscles of the thigh are both so crucial to bipedal activities that each alone is much larger than even the well-developed biceps of the arms.

Nervous system

The famous knee jerk (or patellar reflex

Patellar reflex

The patellar reflex or knee-jerk is a deep tendon reflex and is a myotatic reflex.-Mechanism:Striking the patellar tendon with a tendon hammer just below the patella stretches the sensory nerve fiber of the femoral nerve which synapses at the level of L4 in the spinal cord, completely independent...

) emphasizes the necessary bipedal control system: the only function served by the nerves involved being connected as they are is to ensure quick response to imminent disturbance of erect posture; it not only occurs without conscious mental activity, but also involves none of the nerves which lead from the leg to the brain.

A less well-known aspect of bipedal neuroanatomy

Neuroanatomy

Neuroanatomy is the study of the anatomy and organization of the nervous system. In contrast to animals with radial symmetry, whose nervous system consists of a distributed network of cells, animals with bilateral symmetry have segregated, defined nervous systems, and thus we can begin to speak of...

can be demonstrated in human infants who have not yet developed toward the ability to stand up. They can nevertheless run with great dexterity, provided they are supported in a vertical position and offered the stimulus of a moving treadmill beneath their feet.

Respiration

A biped also has the ability to breathe whilst it runs. Humans usually take a breath every other stride when their aerobic system is functioning. During a sprint, at which point the anaerobic system kicks in, breathing slows until the anaerobic

Anaerobic respiration

Anaerobic respiration is a form of respiration using electron acceptors other than oxygen. Although oxygen is not used as the final electron acceptor, the process still uses a respiratory electron transport chain; it is respiration without oxygen...

system can no longer sustain a sprint.

This is not necessarily an advantage over quadrupeds, as not only can many quadrupeds breathe while running, but in mammals such as dogs, the act of running helps to expand and contract the lungs. The muscles of the trunk thus perform locomotive and respiratory tasks at the same time, making breathing while running more efficient in these animals than in bipeds..

Bipedal robots

For nearly the whole of the 20th century, bipedal robot

Robot

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...

s were very difficult to construct and robot locomotion

Robot locomotion

Robot locomotion is the collective name for the various methods that robots use to transport themselves from place to place. Although wheeled robots are typically quite energy efficient and simple to control, other forms of locomotion may be more appropriate for a number of reasons...

involved only wheels, treads, or multiple legs. Recent cheap and compact computing power has made two-legged robots more feasible. Some notable biped robots are ASIMO

ASIMO

is a humanoid robot created by Honda. Introduced in 2000, ASIMO, which is an acronym for "Advanced Step in Innovative MObility", was created to be a helper to people. With aspirations of helping people who lack full mobility, ASIMO is used to encourage young people to study science and mathematics...

, HUBO

HUBO

HUBO is a walking humanoid robot, head mounted on a life-size walking bipedal frame, developed by the Korea Advanced Institute of Science and Technology and released on January 6, 2005...

and QRIO

QRIO

QRIO was to be a bipedal humanoid entertainment robot developed and marketed by Sony to follow up on the success of its AIBO toy. QRIO stood approximately 0.6 m tall and weighed 7.3 kg...

. Recently, spurred by the success of creating a fully passive, un-powered bipedal walking robot, those working on such machines have begun using principles gleaned from the study of human and animal locomotion, which often relies on passive mechanisms to minimize power consumption.

External links

The Origin of Bipedalism

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