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Quadrupedalism (from Latin, meaning "four legs")
is a form of
land animal locomotion using four legs. The
majority of walking animals are quadrupeds, including mammals such as cattle and cats, and reptiles, like lizards. Birds, humans, insects, crustaceans and snakes are not quadrupeds. There
are some exceptions, for example among the insects the praying
mantis is a quadruped. A few birds may use quadrupedal movement
in some circumstances, for example the shoebill will sometimes use its
wings to right itself after lunging at prey.
Quadrupeds and tetrapods
Not all four-limbed animals are quadrupeds. Although arms and wings are, in the evolutionary sense, modified legs, four-limbed animals are in fact classed as tetrapods – members of the taxonomic unit Tetrapoda. These include all vertebrates with quadrupedal ancestors, including mammals, reptiles, amphibians, and birds. See Pierson v. Post, 3 Cai. R. 175, 2 Am. Dec. 264 (N.Y. 1805), read this case for common law knowledge of quadrupeds ferae naturae.The distinction between quadrupeds and tetrapods
is important in evolutionary biology, particularly in the context
of bipeds, winged animals,
and animals whose limbs have adapted to other roles (e.g. fins, in the case of cetaceans and
pinnipeds). All of
these animals are tetrapods, but none are quadrupeds. Even snakes, whose limbs have become
entirely vestigial,
are nevertheless tetrapods.
Quadrupedalism in humans
In July of 2005, in rural Turkey, scientists discovered five Kurdish siblings who had learned to walk naturally on their hands and feet. Unlike chimpanzees, who ambulate on their knuckles, the Turkish siblings (ranging from 18 to 34 years old) walked on their palms, allowing them to preserve the dexterity of their fingers. Calluses found on their hands make the possibility of a hoax unlikely. Another similar case has been reported in Chile, but the case is still being investigated and reports are not released as of March 22, 2006.The discovery of the family has provided
scientists a unique view into human evolutionary history. Nicholas
Humphrey, a researcher from the
London School of Economics, has suggested
and colleagues have argued that their gait is due to two rare
phenomena coming together. First, instead of initially crawling as
infants on their knees, they started off learning to move around
with a “bear crawl” on their feet. Second, due to their congenital
brain impairment, they found balancing on two legs difficult.
Because this, their motor development was channelled into turning
their bear crawl into a substitute for bipedality.
Other scientists, such as Stefan Mundlos of the
Max
Planck Institute, believe that the family's unusual gait may
result from a genetic abnormality. Mundlos has found a region on
chromosome
17 which might be responsible for human bipedalism.
Quadrupedal Movement for Exercise
Many people, especially practitioners of Parkour and Freerunning and Georges Hébert's Natural Method, find benefit in using quadrupedal movement in order to build full body strength. For added difficulty this can done faster or down stairs. Moving quadrupedally exercises the entire anterior: thighs, core, shoulders, and triceps.See also
External links
quadrupedal in Catalan: Quadrupedisme
quadrupedal in German: Quadrupedie
quadrupedal in Chinese: 四足動物