Bipedalism is a form of terrestrial locomotion where an organism moves by means of its two rear limbs. Terrestrial locomotion has Evolved as Animals adapted from aquatic to terrestrial environments In Physics, motion means a constant change in the location of a body An animal or machine that usually moves in a bipedal manner is known as a biped (pronounced /ˈbaɪpɛd/), meaning "two feet" (Latin bi = two + ped = foot). A machine is any device that uses Energy to perform some activity Latin ( lingua Latīna, laˈtiːna is an Italic language, historically spoken in Latium and Ancient Rome. Types of bipedal movement include walking, running, or hopping, on two appendages (typically legs). Walking (also called ambulation) is the main form of Animal Locomotion on land, distinguished from Running and crawling Running is a means for an animal to move on Foot. It is defined in Sporting terms as a Gait in which at some point all feet are off the ground Jumping or leaping is an ability that most Humans and many Animals share to some degree An appendage in the broadest sense is an additional or subsidiary part existing on or added to something which can generally still function if the appendage has never existed or A leg is a limb on an Animal 's Body that supports the rest of the animal above the ground between the Ankle and the Hip and is used for

Relatively few modern species are habitual bipeds whose normal method of locomotion is two-legged. Within mammals, habitual bipedalism has evolved three times, with the macropods, kangaroo mice and apes. Mammals ( class Mammalia) are a class of Vertebrate Animals characterized by the presence of Sweat glands, including sweat glands Macropods are Marsupials belonging to the family Macropodidae, which includes Kangaroos wallabies, Tree-kangaroos Pademelons A kangaroo mouse is either one of the two Species of jumping mouse ( Genus Microdipodops) native to the deserts of the Southwestern In the Triassic period some groups of archosaurs (a group that includes the ancestors of crocodiles) developed bipedalism; among their descendants the dinosaurs all the early forms and many later groups were habitual or exclusive bipeds; the birds descended from one group of exclusively bipedal dinosaurs. The Triassic is a geologic period and system that extends from about 251 to 199 Ma (million years ago Archosaurs ( Greek for 'ruling lizards' are a group of Diapsid Reptiles represented by Modern birds and Crocodilians This group also A crocodile is any Species belonging to the family Crocodylidae (sometimes classified instead as the Subfamily Crocodylinae) Birds ( class Aves) are bipedal endothermic ( Warm-blooded) Vertebrate animals that lay eggs.

A larger number of modern species are capable of bipedal movement for a short time in exceptional circumstances. Several crocodile species and non-archsaurian lizard species move bipedally when they are in an extreme hurry, usually to escape from threats; and some lizards, inclusing the Jesus lizard, even run bipedally on water. Lizards are a large and widespread group of Reptiles of the order Squamata, with nearly 5000 species and ranging across all continents except The plumed basilisk ( Basiliscus plumifrons) also called a green basilisk, is a Species of Lizard native to Latin America. Many animals rear up on their hind legs while fighting. A few animals commonly stand on their hind legs, in order to reach food or to keep watch, but do not move bipedally.

There are two main types of bipedal locomotion: macropods, smaller birds and kangaroo mice move by hopping on both legs simultaneously; other groups, including apes and large birds, walk or run by moving one leg at a time. ^[1]

Contents 1 Definition 1.1 Facultative and obligate bipedalism 2 Movement 3 Bipedal animals 3.1 Dinosaurs and their descendants 3.2 Mammals 3.3 Limited bipedalism in mammals 3.4 Limited bipedalism in non-mammals 3.5 Advantages 4 Evolution 4.1 Early reptiles and lizards 4.2 Dinosaurs and birds 4.3 Mammals (excluding humans) 4.4 Humans 4.4.1 Postural feeding hypothesis 4.4.2 Provisioning model 4.4.3 Other behavioural models 4.4.4 Thermoregulatory model 4.4.5 Carrying models 4.4.6 Wading hypothesis 4.4.7 Savannah hypothesis 5 Physiology 5.1 Biomechanics 5.1.1 Standing 5.1.2 Walking 5.1.3 Running 5.1.4 Hopping 5.2 Musculature 5.3 Nervous system 5.4 Respiration 6 Bipedal robots 7 Bipedal molecule 8 Notes 9 References

Definition

The word is derived from the Latin words bi(s) 'two' and ped- 'foot', as contrasted with quadruped 'four feet'. The Ostrich ( Struthio camelus) is a large Flightless bird native to Africa (and formerly the Middle East) Eadweard J Muybridge ( April 9, 1830 &ndash May 8, 1904) was an English photographer, known primarily for his early use Latin ( lingua Latīna, laˈtiːna is an Italic language, historically spoken in Latium and Ancient Rome.

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 neurological disorders rather than normal behavior. ^[2] 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 focusses 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.

1. Standing. Standing is a Human position in which the body is constantly in an orthostatic state Staying still on both legs. In most bipeds this is an active process, requiring constant adjustment of balance.
2. Walking. Walking (also called ambulation) is the main form of Animal Locomotion on land, distinguished from Running and crawling One foot in front of another, with at least one foot on the ground at any time.
3. Running. Running is a means for an animal to move on Foot. It is defined in Sporting terms as a Gait in which at some point all feet are off the ground One foot in front of another, with periods where both feet are off the ground.
4. Jumping/Hopping. Jumping or leaping is an ability that most Humans and many Animals share to some degree Moving by a series of jumps with both feet moving together.
5. Jogging. Jogging is a form of trotting or running at a slow or leisurely pace A mix between walking and running, mostly shown in humans.

Bipedal animals

The great majority of living terrestrial vertebrates are quadrupeds. Among mammals, bipedalism is a normal method of ground locomotion in various groups of primates (e. In Biomechanics, animal locomotion is the study of how Animals move. A primate is a member of the biological order Primates ( Latin: "prime first rank" the group that contains Lemurs the Aye-aye g. lemurs, gibbons and Hominina), in the macropods (kangaroos, wallabies, etc. Lemurs make up the infraorder Lemuriformes and are members of a group of Primates known as Prosimians The term "lemur" is derived from the The more Anthropomorphic Primates of the Hominini tribe are placed in the Hominina subtribe Macropods are Marsupials belonging to the family Macropodidae, which includes Kangaroos wallabies, Tree-kangaroos Pademelons ) and in a few groups of rodents (kangaroo mice, spring hares). A kangaroo mouse is either one of the two Species of jumping mouse ( Genus Microdipodops) native to the deserts of the Southwestern The Springhare ( Pedetes capensis) or Springhaas, is not actually a Hare, but a member of the order Rodentia it is the only species in its All birds are bipeds when on the ground, a feature inherited from their dinosaur ancestors. Birds ( class Aves) are bipedal endothermic ( Warm-blooded) Vertebrate animals that lay eggs. Bipedalism evolved more than once in archosaurs, the group that includes both dinosaurs and crocodilians. Archosaurs ( Greek for 'ruling lizards' are a group of Diapsid Reptiles represented by Modern birds and Crocodilians This group also Crocodilia is an order of large Reptiles that appeared about 84 million years ago in the late Cretaceous Period ( Campanian stage ^[3] A few lizards can also move bipedally, but only in emergencies. Lizards are a large and widespread group of Reptiles of the order Squamata, with nearly 5000 species and ranging across all continents except 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 by raising one foot at a time. Walking (also called ambulation) is the main form of Animal Locomotion on land, distinguished from Running and crawling On the other hand macropods, smaller birds and bipedal rodents move by hopping on both legs simultaneously.

Dinosaurs and their descendants

All dinosaurs are believed to be descended from a fully bipedal ancestor, perhaps similar to Eoraptor. Eoraptor was one of the world's earliest Dinosaurs It was a two-legged meat-eater that lived between 230 and 225  Million years ago It is believe that maniraptors were able to reach speeds of up to 65 km/h moving bipedally, comparable to their large, flightless-bird descendants such as the ostrich. Maniraptora ("hand snatchers" is a Clade of Coelurosaurian Dinosaurs which includes the Birds and the dinosaurs that were more closely The Ostrich ( Struthio camelus) is a large Flightless bird native to Africa (and formerly the Middle East) Bipedal movement also re-evolved in a number of other dinosaur lineages such as the iguanodons. Iguanodon (ɪˈgwɑːnədɒn or /ɪˈgwænədɒn/ meaning " Iguana Tooth " is a Genus of Ornithopod Dinosaur Some extinct members of the crocodilian line, a sister group to the dinosaurs and birds, also evolved bipedal forms - a crocodile relative from the triassic, Effigia okeeffeae, was believed to be bipedal. Crocodilia is an order of large Reptiles that appeared about 84 million years ago in the late Cretaceous Period ( Campanian stage A crocodile is any Species belonging to the family Crocodylidae (sometimes classified instead as the Subfamily Crocodylinae) The Triassic is a geologic period and system that extends from about 251 to 199 Ma (million years ago Effigia was an Archosaur that lived in what is now New Mexico. ^[4]

Mammals

Bipedal movement is less common among mammals, most of which are quadrupedal. Mammals ( class Mammalia) are a class of Vertebrate Animals characterized by the presence of Sweat glands, including sweat glands Quadrupedalism (from Latin meaning "four legs" is a form of land animal locomotion using four legs. The largest mammalian group using bipedal movement are the macropods (kangaroos, wallabies and their relatives), which move via hopping. Macropods are Marsupials belonging to the family Macropodidae, which includes Kangaroos wallabies, Tree-kangaroos Pademelons Other mammals also move via hopping, such as the kangaroo rat, springhare and certain primates such as the sifaka and sportive lemur. Kangaroo rats, genus Dipodomys, are small Rodents native to North America. The Springhare ( Pedetes capensis) or Springhaas, is not actually a Hare, but a member of the order Rodentia it is the only species in its Sifakas are a Genus ( Propithecus) from the Primate family Indriidae. The sportive lemurs are the medium sized Primates that make up the Lepilemuridae family Possibly the only mammals other than humans that commonly move bipedally by an alternating gait rather than hopping are gibbons when on the ground, and giant pangolins. Gibbons are the small Apes in the family Hylobatidae. The family is divided into four genera based on their Diploid Chromosome The Giant Pangolin ( Manis gigantea) is a Pangolin Species. Members of the species inhabit Africa with a range stretching along the

Limited bipedalism in mammals

Other mammals engage in limited, non-locomotory, bipedalism. The bonobo and proboscis monkey both live in forests that are often flooded and will wade through water in a bipedal stance; along with other primates, they will also walk or stand bipedely on land, though generally for short periods. The Bonobo (bə'noʊboʊ Pan paniscus) until recently usually called the Pygmy Chimpanzee (and less often the Dwarf or Gracile Chimpanzee The Proboscis Monkey ( Nasalis larvatus) also known as the Monyet Belanda (in Malay) the Bangkatan (in Indonesian) or simply Three captive primates, one macaque Natasha^[5] and two chimps, Oliver and Poko, were found to move bipedally. Natasha is a black macaque at the Safari Park zoo near Tel Aviv, Israel. Oliver is a Common Chimpanzee and a former performing ape once promoted as a missing link or " Humanzee " due Natasha switched to exclusive bipedalism after an illness, while Poko was discovered in captivity in a tall, narrow cage [1] [2]. Oliver reverted to knuckle-walking after developing arthritis. Gorillas and Chimpanzees use a style of Locomotion called knuckle-walking, where they walk on all fours with the fingers of their forelimbs held A number of other animals, such as rats, racoons, and beavers will squat on their hindlegs in order to manipulate some objects but revert to four limbs when moving (the beaver may also move bipedally if transporting wood for their dams). Rats are various medium sized long-tailed Rodents of the superfamily Muroidea The raccoon ( Procyon lotor) (sometimes spelt as racoon) also known as the common raccoon, North American raccoon, northern raccoon Beavers are two primarily nocturnal semi-aquatic species of Rodent, one native to North America and one to Europe Beavers are two primarily nocturnal semi-aquatic species of Rodent, one native to North America and one to Europe Bears will fight in a bipedal stance in order to use their forelegs as weapons. Ground squirrels and meerkats will stand on hind legs to survey their surroundings, but will not walk bipedally. The ground squirrels are the members of the Sciuridae most closely related to the Genus Marmota. The meerkat or suricate Suricata suricatta is a small Mammal and a member of the Mongoose family Dogs can stand or move on two legs if trained, or if birth defect or injury precludes quadrupedalism. The dog ( Canis lupus familiaris) is a domesticated Subspecies of the gray wolf, a Mammal of the Canidae family of the order Quadrupedalism (from Latin meaning "four legs" is a form of land animal locomotion using four legs. The gerenuk antelope stands on its hind legs while eating from trees, as did the extinct giant ground sloth and chalicotheres. Gerenuks, Litocranius walleri, are a type of antelope/gazelle with remarkably long necks that are found in East Africa Megatherium ("Great Beast" was a Genus of Elephant -sized Ground sloths that lived from two million to 8000 years ago Chalicotheres (from Greek chalix, gravel + therion, beast were a group of perissodactyl Mammals that evolved in the mid Eocene The spotted skunk will also use limited bipedalism when threatened, rearing up while facing the attacker so its anal glands, capable of spraying an offensive oil, face its attacker. The spotted skunks are three species of Skunk in the genus Spilogale. The anal glands or anal sacs are small paired sacs located on either side of the anus between the external and internal sphincter muscles.

Limited bipedalism in non-mammals

Bipedalism is unknown among the amphibians. Prehistoric amphibian Amphibians (class Amphibia such as Frogs Toads Salamanders Newts Gymnophiona, Sirens and Among the non-archosaur reptiles bipedalism is rare, but it is found in the 'reared-up' running of certain lizards and monitor lizards will also temporarily adopt bipedalism while fighting. Archosaurs ( Greek for 'ruling lizards' are a group of Diapsid Reptiles represented by Modern birds and Crocodilians This group also Reptiles, or members of the class Reptilia are air-breathing Cold-blooded Vertebrates that have skin covered in scales as opposed to hair or feathers Lizards are a large and widespread group of Reptiles of the order Squamata, with nearly 5000 species and ranging across all continents except Monitor lizards are the family Varanidae, a group of carnivorous lizards which includes the largest living lizard the Komodo dragon. ^[6] One genus of basilisk lizard can run bipedally across the surface of water for some distance. Basiliscus is a Genus of Lizards that includes the basilisks Taxonomy and etymology The Genus basiliscus is named for the creature Bipedalism in the form of reared-up running can also be found in cockroaches, but is otherwise unknown in arthropods. Cockroaches (or simply "roaches" are Insects of the order Blattaria. Arthropods are Animals belonging to the Phylum Arthropoda (from Greek ἄρθρον arthron, " Joint " Bipedalism is virtually solely found in terrestrial animals, though at least two types of octopus 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. Terrestrial animals are Animals that live predominantly or entirely on land as compared with Aquatic animals which live predominantly or entirely in the water (e The ^[7]

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 limbs 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). A limb (from the Old English lim) is a jointed or Prehensile (as Octopus tentacles or new world Monkey tails Appendage of the 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 quadrapedal movement with a flexible backbone - the ostrich reaches speeds of 65 km/h and the red kangaroo 70 km/h, while the cheetah can exceed 100 km/h. The Ostrich ( Struthio camelus) is a large Flightless bird native to Africa (and formerly the Middle East) The Red Kangaroo ( Macropus rufus) is the largest of all Kangaroos the largest Mammal native to Australia, and the largest surviving The cheetah ( Acinonyx jubatus) is an atypical member of the cat family ( Felidae) that is unique in its speed while lacking climbing abilities

Evolution

Recent evidence regarding modern human sexual dimorphism (physical differences between men and women) in the lumbar spine has been seen in pre-modern primates such as Australopithecus africanus. Sexual dimorphism is the systematic difference in form between individuals of different Sex in the same Species. The lumbar vertebrae are the largest segments of the movable part of the Vertebral column, and are characterized by the absence of the Foramen transversarium within Australopithecus africanus was an early hominid, an Australopithecine, who lived between 2-3 million years ago in the Pliocene. This dimorphism has been seen as an evolutionary adaptation of females to better bear lumbar load during pregnancy, an adaptation that non-bipedal primates would not need to make. Pregnancy ( Latin graviditas) is the carrying of one or more offspring known as a Fetus or Embryo, inside the Uterus of a Female ^[8][9]

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 Eudibamus whose fossils date from 290 million years ago. Bolosaurids are an Extinct family of Anapsid Reptiles from the Permian Period Eudibamus is an Extinct Genus of Biped Bolosaurid (a reptile from the early Permian some 290 million years ago of ^[10][11] 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 developed independently among the dinosaurs. Dinosaurs diverged from their archosaur ancestors approximately 230 million years ago during the Middle to Late Triassic period, roughly 20 million years after the Permian-Triassic extinction event wiped out an estimated 95% of all life on Earth. Archosaurs ( Greek for 'ruling lizards' are a group of Diapsid Reptiles represented by Modern birds and Crocodilians This group also The Triassic is a geologic period and system that extends from about 251 to 199 Ma (million years ago The Permian–Triassic (P–Tr extinction event, informally known as the Great Dying, was an Extinction event that occurred, and 70 percent of terrestrial ^[12][13] Radiometric dating of fossils from the early dinosaur genus Eoraptor establishes its presence in the fossil record at this time. Radiometric dating (often called radioactive dating) is a technique used to date materials usually based on a comparison between the observed abundance of a naturally occurring A genus (plural genera from Γένος Latin genus "descent family type gender" is a low-level Taxonomic Eoraptor was one of the world's earliest Dinosaurs It was a two-legged meat-eater that lived between 230 and 225  Million years ago Paleontologists believe Eoraptor resembles the common ancestor of all dinosaurs;^[14] if this is true, its traits suggest that the first dinosaurs were small, bipedal predators. A group of organisms is said to have common descent if they have a common Ancestor. ^[15] The discovery of primitive, dinosaur-like ornithodirans such as Marasuchus and Lagerpeton in Argentinian Middle Triassic strata supports this view; analysis of recovered fossils suggests that these animals were indeed small, bipedal predators. Marasuchus is a genus of Dinosaur -like Ornithodiran from the middle Triassic Period of Argentina. Lagerpeton is the name given to a genus of basal dinosauromorph from the Ladinian (Middle Triassic) For a topic outline on this subject see List of basic Argentina topics. The Middle Triassic (also known as Muschelkalk) is the second of three epochs of the Triassic period.

Mammals (excluding humans)

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 pangolins, and macropods. The Giant Pangolin ( Manis gigantea) is a Pangolin Species. Members of the species inhabit Africa with a range stretching along the Macropods are Marsupials belonging to the family Macropodidae, which includes Kangaroos wallabies, Tree-kangaroos Pademelons 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. ^[16]

Humans

Main article: Human skeletal changes due to bipedalism

There are at least twelve distinct hypotheses as to how and why bipedalism evolved in humans, and also some debate as to when. The evolution of Bipedalism approximately four million years ago has led to significant changes in the Anatomy of Homo sapiens. Evidence points to bipedalism evolving before the expansion in human brain size. The different hypotheses are not necessarily mutually exclusive and a number of selective forces may have acted together to lead to human bipedalism.

Various reasons have been proposed for the evolution of human bipedalism, including freeing the hands for tool use and carrying, sexual dimorphism in food gathering, changes in climate and habitat (from jungle to savanna) and to reduce the amount of skin exposed to the tropical sun. Sexual dimorphism is the systematic difference in form between individuals of different Sex in the same Species. Jungle usually refers to a dense Forest in a hot climate such as a Tropical rainforest. A savanna or savannah is a Tropical or Subtropical Grassland or Woodland Ecosystem. The first two explanations have been criticized for projecting modern social concerns and prejudices onto ancestral species. The latter two have been criticized for not making sense in the context of the forest and woodland biomes occupied by human ancestors. A biome is a climatically and geographically defined area of ecologically similar climatic conditions such as communities of Plants Animals and An alternative explanation is the mixture of savanna and scattered woods forced proto-humans to travel between clusters of trees and bipedalism offered greater efficiency for slow, long-distance travel between these clusters than knuckle-walking quadrupedism. ^[17]

Postural feeding hypothesis

The postural feeding hypothesis has been recently supported by Dr. Kevin Hunt, a professor at Indiana University. This theory 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 theorizes that these movements coevolved with chimpanzee arm-hanging, as this movement was very effective and efficient in harvesting food. Chimpanzee (often shortened to chimp) is the common name for the two extant Species of Apes in the Genus Pan. When analyzing fossil anatomy, Australopithecus afarensis has very similar features of the hand and shoulder to the chimpanzee, which indicates hanging arms. Australopithecus afarensis is an extinct Hominid which lived between 3 Also, the Australopithecus hip and hind limb very clearly indicate bipedalism, but these fossils also indicate very inefficient locomotive movement when compared to humans. The Genus Australopithecus ( Latin australis "of the south" Greek πίθηκος pithekos "ape" Human beings, humans or man (Origin 1590–1600 L homō man OL hemō the earthly one (see Humus 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 for the fully realized locomotor bipedalism apparent in Homo erectus. ” A related hypothesis is that proto-humans learned upright posture not for picking fruit, as it is argued they would have stayed climbers if plucking fruit were all they were after, rather they learned to keep their head out of the water while searching for water plants, mollusca, and the like.

Provisioning model

One of the most elaborate theories on the origin of bipedalism is the behavioral model presented by C. Owen Lovejoy, which is known as "male provisioning". ^[18] Lovejoy theorizes that the evolution of bipedalism was a response to a monogamous society. eVolution is the third Album by eLDee, it was due to be released in 2008 As hominid males became monogamous, they would leave their families for the day in order to search for food. A hominid is any member of the biological family Hominidae (the "great apes" including the extinct and extant Humans Chimpanzees Once they found food for their family, the hominids would have to bring back the food, and the most effective way of doing this was through bipedalism.

There is some question over whether or not early hominids were monogamous. Some evidence indicates that early hominids, which were proven to be bipedal, were in fact polygamous. Among all monogamous primates, sexual dimorphism is greatly decreased. Sexual dimorphism is the systematic difference in form between individuals of different Sex in the same Species. In Australopithecus afarensis, males were found to be nearly twice the weight of females (as well as a great deal taller), an attribute scientists would expect in a polygamous species. Australopithecus afarensis is an extinct Hominid which lived between 3 Lastly, monogamous primates are highly territorial, but fossil evidence indicates that Australopithecus afarensis lived in large groups. Overall, there is no concrete evidence to thoroughly discount or prove monogamy or polygamy in early hominids.

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 and most fanciful theories on the table, 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.

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 hypothesis

Main article: Aquatic ape hypothesis

The Aquatic ape hypothesis proposes that humans evolved bipedalism as a result of bipedal wading. The aquatic ape hypothesis (AAH, sometimes referred to as the aquatic ape theory, asserts that wading swimming and diving for food exerted a strong Evolutionary effect The aquatic ape hypothesis (AAH, sometimes referred to as the aquatic ape theory, asserts that wading swimming and diving for food exerted a strong Evolutionary effect Mammals that switch from quadrupedalism on land to bipedal wading appear mainly to be found among large primates, especially apes, with relatively few exceptions such as the grizzly bear. The Grizzly Bear (Ursus arctos horribilis, also known as the Silvertip Bear, is a Subspecies of Brown bear (Ursus arctos that lives Bipedal wading has been observed in the bonobo, chimpanzee, lowland gorilla, orangutan, baboon and proboscis monkey. The Bonobo (bə'noʊboʊ Pan paniscus) until recently usually called the Pygmy Chimpanzee (and less often the Dwarf or Gracile Chimpanzee Chimpanzee (often shortened to chimp) is the common name for the two extant Species of Apes in the Genus Pan. Gorillas, the largest of the living Primates are ground-dwelling Herbivores that inhabit the Forests of Africa. The orangutans are two Species of great apes known for their intelligence long arms and reddish-brown hair The baboons are African Old World monkeys belonging to the genus Papio, part of the subfamily Cercopithecinae. The Proboscis Monkey ( Nasalis larvatus) also known as the Monyet Belanda (in Malay) the Bangkatan (in Indonesian) or simply Bipedal wading provides the advantage of keeping the head above water for breathing.

Savannah hypothesis

This proposes that the onset of drier conditions severely reduced the amount of wooded habitats. During this period, when the forests became thin, early hominids adapted to an environment which was now more like the liminal forest-savanna mosaic zones of equatorial Africa. Liminality (from the Latin Forest-savanna mosaic is a transition zone between the tropical moist broadleaf forests of equatorial Africa and the drier savannas and open woodlands to the north In order to remain effective in gathering food, the hominids had to travel relatively long distances with food or tools, thus making quadrupedalism extremely inefficient. Bipedalism developed both as an adaptation to facilitate movement across the grasslands and as a way to give early hominids use of their hands for food cultivation and tool use since they were no longer needed for locomotion. A hominid is any member of the biological family Hominidae (the "great apes" including the extinct and extant Humans Chimpanzees

Physiology

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

Biomechanics

Engineers who study bipedal walking or running describe it as a repeatedly interrupted fall. The phenomenon of "tripping" is informative with regards to the "controlled falling" concept of walking and running. The common way to think of tripping is as pulling a leg out from under a walker or runner. In fact, however, merely stopping the movement of one leg of a walker, and merely slowing one leg of a runner, is sufficient to amount to tripping them. They were already "falling", and preventing the tripped leg from aborting that fall is sufficient to cause bipeds to collapse to the ground.

Standing

Energy-efficient means of standing bipedally involve constant adjustment of balance, and of course these must avoid overcorrection. Feedback is a circular causal Process whereby some proportion of a system's output is returned (fed back to the Input.

Walking

Efficient walking is more complicated than standing. It entails tipping slightly off-balance forward and to the side, and correcting balance with the right timing. In humans, walking is composed of several separate processes:

• rocking back and forth between feet
• pushing with the toe to maintain speed
• combined interruption in rocking and ankle twist to turn
• shortening and extending the knees to prolong the "forward fall"

Running

Running is an inherently continuous process, in contrast to walking; a bipedal creature or device, when efficiently running, is in a constant state of falling forward. This is maintained as relatively smooth motion only by repeatedly "catching oneself" with the right timing, but in the case of running only delaying the otherwise inevitable fall for the duration of another step.

Hopping

Musculature

Bipedalism requires strong leg muscles, particularly in the thighs. Contrast in domesticated poultry the well muscled legs, against the small and bony wings. Domestication (from Latin domesticus) refers to the process whereby a Population of Animals Poultry is the category of Domesticated Birds which some humans keep for the purpose of collecting their eggs, or kill for their Meat and/or Likewise in humans, the quadriceps and hamstring 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. "Quads" redirects here For other uses see Quad The quadriceps femoris ( Latin for "four-headed of the femur" also In Human anatomy, a hamstring refers to one of the Tendons that make up the borders of the space behind the knee

Nervous system

The famous knee jerk (or patellar reflex) 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. The patellar reflex or knee-jerk is a Stretch reflex and is a Myotatic reflex.

A less well-known aspect of bipedal neuroanatomy can be demonstrated in human infants who have not yet developed toward the ability to stand up. Neuroanatomy is the science for localizing function in the Human brain. 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. Cellular respiration is the set of the metabolic reactions and processes that take place in Organisms cells to convert biochemical energy from During a sprint, at which point the anaerobic system kicks in, breathing slows until the anaerobic system can no longer sustain a sprint. See also Fermentation (biochemistry Anaerobic respiration (anaerobiosis refers to the Oxidation of molecules in the absence of Oxygen to produce

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

Main article: humanoid robot

For nearly the whole of the 20th century, bipedal robots were very difficult to construct and robot locomotion involved only wheels, treads, or multiple legs. A Humanoid Robot is a Robot with its overall appearance based on that of the Human body. is a Humanoid robot created by Honda Motor Company. Standing at 130 Centimeters (4 feet 3 Inches) and weighing 54 Kilograms (119 A robot is a mechanical or Virtual Artificial agent In practice it is usually an electro-mechanical system which by its appearance or movements Robot locomotion is the study of how to design Robot appendages and control mechanisms to allow robots to move fluidly and efficiently Recent cheap and compact computing power has made two-legged robots more feasible. Some notable biped robots are ASIMO, HUBO and QRIO. is a Humanoid robot created by Honda Motor Company. Standing at 130 Centimeters (4 feet 3 Inches) and weighing 54 Kilograms (119 HUBO (휴보 KHR-3 is a walking Humanoid robot, head mounted on a life-size walking Bipedal frame developed by the Korea Advanced Institute of Science and Technology QRIO (" Q uest for cu' RIO' sity" originally named Sony

Bipedal molecule

In 2005, chemists at the University of California, Riverside developed the first bipedal molecule, 9,10-Dithioanthracene, which propels itself in a straight line when heated on a flat copper surface. The University of California Riverside, commonly known as UCR or UC Riverside, is a public Research university and one of the 10 general 910-Dithioanthracene (DTA is the first Molecule ever to be able to "walk" in a straight line by in effect mimicking the bipedal motion of Researchers believe the molecule has potential for use in molecular computers. Molecular computers are massively parallel computers taking advantage of the computational power of molecules (specifically biological

Notes

References

• Darwin, C., "The Descent of Man and Selection in Relation to Sex", Murray (London), (1871). Charles Robert Darwin (February 12 1809 &ndash April 19 1882 was an English naturalist, who realised and demonstrated that all Species of life
• Dart, R. A. , "Australopithecus africanus: The Ape Man of South Africa" Nature, 145, 195-199, (1925).
• Dawkins, R., "The Ancestor's Tale", Weidenfeld and Nicolson (London), (2004). Clinton Richard Dawkins, FRS, FRSL (born 26 March 1941 is a British ethologist, evolutionary biologist, and Popular science
• Hardy, Alistair Hardy, "Was Man More Aquatic in the Past?," The New Scientis, 17 March 1960, pp. 642-645, U. of Victoria (1960)
• Hewes, G. W. , "Food Transport and the Origin of Hominid Bipedalism" American Anthropologist, 63, 687-710, (1961).
• Hunt, K. D. , "The Evolution of Human Bipedality" Journal of Human Evolution, 26, 183-202, (1994).
• Isaac, G. I. , "The Archeological Evidence for the Activities of Early African Hominids" In:Early Hominids of Africa (Jolly, C. J. (Ed. )), Duckworth (London), 219-254, (1978).
• Jablonski, N. G. & Chaplin, G. "Origin of Habitual Terrestrial Bipedalism in the Ancestor of the Hominidae", Journal of Human Evolution, 24, 259-280, (1993).
• Kuliukas A (2002). "html Wading for food the driving force of the evolution of bipedalism?". Nutrition and health (Berkhamsted, Hertfordshire) 16 (4): 267–89. PMID 12617279.  
• Lovejoy, C. O. , "The Origin of Man. " Science, 211, 341-350, (1981).
• Morgan, E., "The Aquatic Ape: A theory of Human Evolution," Souvenir Press, London (1982). Elaine Morgan (writer is a Welsh writer and advocate of the Aquatic ape hypothesis
• Tanner, N. M. , "On Becoming Human", Cambridge University Press (Cambridge), (1981).
• Wescott, R. W. , "Hominid Uprightness and Primate Display", American Anthropologist, 69, 738,(1967).
• Wheeler, P. E. , "The Evolution of Bipedality and Loss of Functional Body Hair in Hominoids. " Journal of Human Evolution, 13, 91-98, (1984).
• Vrba, E. , "The Pulse that Produced Us. " Natural History, 102(5), 47-51, (1993).

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