Brachiation

Last updated
Brachiating primates such as this siamang (Symphalangus syndactylus) have long forelimbs and curved fingers Brachiate.jpg
Brachiating primates such as this siamang (Symphalangus syndactylus) have long forelimbs and curved fingers

Brachiation (from "brachium", Latin for "arm"), or arm swinging, is a form of arboreal locomotion in which primates swing from tree limb to tree limb using only their arms. During brachiation, the body is alternately supported under each forelimb. This form of locomotion is the primary means of locomotion for the small gibbons and siamangs of southeast Asia. Gibbons in particular use brachiation for as much as 80% of their locomotor activities. [1] Some New World monkeys, such as spider monkeys and muriquis, were initially classified as semibrachiators and move through the trees with a combination of leaping and brachiation. Some New World species also practice suspensory behaviors by using their prehensile tail, which acts as a fifth grasping hand. [2] Evidence has shown that the extinct ape Proconsul from the Miocene of East Africa developed an early form of suspensory behaviour, and was therefore referred to as a probrachiator. [3]

Contents

Upon further observations and more in depth understandings of the anatomy and behaviour of primates, the terms semibrachiator and probrachiator have largely fallen out of favour within the scientific community. [3] Currently, researchers classify gibbons and siamangs as the only true brachiators and classify the great apes as modified brachiators. [3] All other brachiation behaviours that do not meet either of these classifications are referred to as forearm suspensory postures and locomotion. [3]

Some traits that allow primates to brachiate include a short spine (particularity the lumbar spine), short fingernails (instead of claws), long curved fingers, reduced thumbs, long forelimbs and freely rotating wrists. [2] Modern humans retain many physical characteristics that suggest a brachiator ancestor, including flexible shoulder joints and fingers well-suited for grasping. In lesser apes, these characteristics were adaptations for brachiation. Although great apes do not normally brachiate (with the exception of orangutans), human anatomy suggests that brachiation may be an exaptation to bipedalism, and healthy modern humans are still capable of brachiating. [4] Some children's parks include monkey bars which children play on by brachiating.

As well as shaping the evolution of gibbon body structure, brachiation has influenced the style and order of their behaviour. For example, unlike other primates who carry infants on their back, gibbons will carry young ventrally. It also affects their play activities, copulation, and fighting. It is thought that gibbons gain evolutionary advantages through brachiation and being suspended by both hands (bimanual suspension) when feeding. While smaller primates cannot hold themselves by both hands for long periods, and larger primates are too heavy to exploit food resources on the ends of branches, gibbons can remain suspended for a significant period and use their long arms to reach food in terminal branches more easily. Another theory postulates that brachiation is a quieter and less obvious mode of locomotion than quadrupedal jumping and climbing thereby more successfully avoiding predators. [5]

Types of brachiation

Continuous contact

This form of brachiation occurs when the primate is moving at slower speeds and is characterized by the animal maintaining constant contact with a handhold, such as a tree branch. [6] This gait type utilizes the passive exchange between two types of energy, gravitational potential and translational kinetic, to propel the animal forward at a low mechanical cost. [6] This mode of brachiation has been compared to the movement patterns of bipedal walking in humans. [7]

Ricochetal

This type of brachiation is used by primates to move at faster speeds and is characterized by a flight phase between each contact with a handhold. [8] Ricochetal brachiation uses an exchange of translational and rotational kinetic energy to move forward, and is compared to a "whip-like" motion. [7] Due to its aerial phase, ricochetal brachiation is similar to bipedal running in humans. [7]

Models of brachiation

Pendulum movement

Continuous contact brachiation has often been compared to the movement of a simple pendulum. [8] This is due to the out-of-phase fluctuation of energy that occurs while the moving primate is swinging between each tree appendage as the energy transfers from potential to kinetic, and vice versa. [9] The use of gravitational acceleration to effect movement can be found in both the brachiating primate and the moving ball in a pendulum model. [9] A brachiator can make use of this momentum in several different ways: during the downswing the primate can maximize its change in kinetic energy, during the upswing it can minimize loss of kinetic energy or it can avoid moving laterally during its upward swing. [9] Brachiating primates have adapted these three strategies for maximizing forward movement by adjusting its posture during each swing. [9]

The amount of energy transferred from potential to kinetic during pendulum-like movement is known as energy recovery. [8] Maintaining a higher energy recovery during brachiation costs less energy and allows the animal to move to its destination quickly, however, this type of movement is also harder to control. [8] Therefore, since the risk of missing a handhold can result in injury or death, the benefit of moving slower with a lower energy recovery and more control likely outweighs the cost of extra energy expenditure. [8]

Evolution of brachiation

Brachiation originated in Africa, thirteen million years ago.[ citation needed ] The emergence of bigger primates that learn to move hanging around by branches obliges the new generations to make some corporal changes that have lasted until today, in many species, including the humans.

Specialized locomotor behaviours, such as brachiating, are thought to have evolved from arboreal quadrupedalism. This behaviour is the ancestral and most common locomotor mechanism among primates. [10] This would explain why living apes and humans share many unusual morphological aspects of the upper limb and thorax. [10] The transition to brachiation is regarded as a major shift during primate evolution and is thought to be a possible precursor to the adaptation of bipedal walking in early hominids. [11] Specialized suspensory behaviour was shown to have evolved independently between hominid groups. [11]

There are several hypotheses for how early brachiating primates may have transitioned into bipedalism. The most generally accepted of these is the vertical climbing hypothesis, which states that vertical climbing is the biomechanical link between brachiation and bipedalism. [12] [13] Many climbing adaptations have been found in early hominins and some of these adaptations can still be seen in present day humans. The distinctive body posture, limb proportions and trunk design identified in living apes are better explained by the previous adaptation of climbing behaviours. [13]

See also

Related Research Articles

<span class="mw-page-title-main">Bipedalism</span> Terrestrial locomotion using two limbs

Bipedalism is a form of terrestrial locomotion where an animal moves by means of its two rear limbs or legs. An animal or machine that usually moves in a bipedal manner is known as a biped, meaning 'two feet'. Types of bipedal movement include walking or running and hopping.

<span class="mw-page-title-main">Walking</span> Gait of locomotion among legged animals

Walking is one of the main gaits of terrestrial locomotion among legged animals. Walking 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. This applies regardless of the usable number of limbs—even arthropods, with six, eight, or more limbs, walk. In humans, walking has health benefits including improved mental health and reduced risk of cardiovascular disease and death.

<span class="mw-page-title-main">Gibbon</span> Family of apes

Gibbons are apes in the family Hylobatidae. The family historically contained one genus, but now is split into four extant genera and 20 species. Gibbons live in subtropical and tropical forests from eastern Bangladesh to Northeast India to southern China and Indonesia.

<i>Australopithecus afarensis</i> Extinct hominid from the Pliocene of East Africa

Australopithecus afarensis is an extinct species of australopithecine which lived from about 3.9–2.9 million years ago (mya) in the Pliocene of East Africa. The first fossils were discovered in the 1930s, but major fossil finds would not take place until the 1970s. From 1972 to 1977, the International Afar Research Expedition—led by anthropologists Maurice Taieb, Donald Johanson and Yves Coppens—unearthed several hundreds of hominin specimens in Hadar, Ethiopia, the most significant being the exceedingly well-preserved skeleton AL 288-1 ("Lucy") and the site AL 333. Beginning in 1974, Mary Leakey led an expedition into Laetoli, Tanzania, and notably recovered fossil trackways. In 1978, the species was first described, but this was followed by arguments for splitting the wealth of specimens into different species given the wide range of variation which had been attributed to sexual dimorphism. A. afarensis probably descended from A. anamensis and is hypothesised to have given rise to Homo, though the latter is debated.

<i>Oreopithecus</i> Extinct genus of hominid from the Miocene

Oreopithecus is an extinct genus of hominoid primate from the Miocene epoch whose fossils have been found in today's Tuscany and Sardinia in Italy. It existed nine to seven million years ago in the Tusco-Sardinian area when this region was an isolated island in a chain of islands stretching from central Europe to northern Africa in what was becoming the Mediterranean Sea.

<span class="mw-page-title-main">Lar gibbon</span> Species of ape

The lar gibbon, also known as the white-handed gibbon, is an endangered primate in the gibbon family, Hylobatidae. It is one of the better-known gibbons and is often kept in captivity.

<i>Australopithecus africanus</i> Extinct hominid from South Africa

Australopithecus africanus is an extinct species of australopithecine which lived between about 3.3 and 2.1 million years ago in the Late Pliocene to Early Pleistocene of South Africa. The species has been recovered from Taung, Sterkfontein, Makapansgat, and Gladysvale. The first specimen, the Taung child, was described by anatomist Raymond Dart in 1924, and was the first early hominin found. However, its closer relations to humans than to other apes would not become widely accepted until the middle of the century because most had believed humans evolved outside of Africa. It is unclear how A. africanus relates to other hominins, being variously placed as ancestral to Homo and Paranthropus, to just Paranthropus, or to just P. robustus. The specimen "Little Foot" is the most completely preserved early hominin, with 90% of the skeleton intact, and the oldest South African australopith. However, it is controversially suggested that it and similar specimens be split off into "A. prometheus".

<span class="mw-page-title-main">Knuckle-walking</span> Form of quadrupedal walking using the knuckles

Knuckle-walking is a form of quadrupedal walking in which the forelimbs hold the fingers in a partially flexed posture that allows body weight to press down on the ground through the knuckles. Gorillas and chimpanzees use this style of locomotion, as do anteaters and platypuses.

The obstetrical dilemma is a hypothesis to explain why humans often require assistance from other humans during childbirth to avoid complications, whereas most non-human primates give birth unassisted with relatively little difficulty. This occurs due to the tight fit of the fetal head to the maternal birth canal, which is additionally convoluted, meaning the head and therefore body of the infant must rotate during childbirth in order to fit, unlike in other, non-upright walking mammals. Consequently, there is an unusually high incidence of cephalopelvic disproportion and obstructed labor in humans.

Orthograde is a term derived from Greek ὀρθός, orthos + Latin gradi that describes a manner of walking which is upright, with the independent motion of limbs. Both New and Old World monkeys are primarily arboreal, and they have a tendency to walk with their limbs swinging in parallel to one another. This differs from the manner of walking demonstrated by the apes.

Henry Malcolm McHenry is a professor of anthropology at the University of California, Davis, specializing in studies of human evolution, the origins of bipedality, and paleoanthropology.

A facultative biped is an animal that is capable of walking or running on two legs (bipedal), as a response to exceptional circumstances (facultative), while normally walking or running on four limbs or more. In contrast, obligate bipedalism is where walking or running on two legs is the primary method of locomotion. Facultative bipedalism has been observed in several families of lizards and multiple species of primates, including sifakas, capuchin monkeys, baboons, gibbons, gorillas, bonobos and chimpanzees. Several dinosaur and other prehistoric archosaur species are facultative bipeds, most notably ornithopods and marginocephalians, with some recorded examples within sauropodomorpha. Different facultatively bipedal species employ different types of bipedalism corresponding to the varying reasons they have for engaging in facultative bipedalism. In primates, bipedalism is often associated with food gathering and transport. In lizards, it has been debated whether bipedal locomotion is an advantage for speed and energy conservation or whether it is governed solely by the mechanics of the acceleration and lizard's center of mass. Facultative bipedalism is often divided into high-speed (lizards) and low-speed (gibbons), but some species cannot be easily categorized into one of these two. Facultative bipedalism has also been observed in cockroaches and some desert rodents.

<span class="mw-page-title-main">Tripedalism</span> Locomotion by use of three limbs

Tripedalism is locomotion by the use of three limbs. Real-world tripedalism is rare, in contrast to the common bipedalism of two-legged animals and quadrupedalism of four-legged animals. The code for bilateral symmetry seems to have become entrenched very early in evolution, appearing even before appendages like legs, fins or flippers had evolved; with that template came a built-in bias toward even-numbered limb configurations.

<span class="mw-page-title-main">Arboreal locomotion</span> Movement of animals through trees

Arboreal locomotion is the locomotion of animals in trees. In habitats in which trees are present, animals have evolved to move in them. Some animals may scale trees only occasionally, but others are exclusively arboreal. The habitats pose numerous mechanical challenges to animals moving through them and lead to a variety of anatomical, behavioral and ecological consequences as well as variations throughout different species. Furthermore, many of these same principles may be applied to climbing without trees, such as on rock piles or mountains.

<span class="mw-page-title-main">Human skeletal changes due to bipedalism</span> Evoltionary changes to the human skeleton as a consequence of bipedalism

The evolution of human bipedalism, which began in primates approximately four million years ago, or as early as seven million years ago with Sahelanthropus, or approximately twelve million years ago with Danuvius guggenmosi, has led to morphological alterations to the human skeleton including changes to the arrangement, shape, and size of the bones of the foot, hip, knee, leg, and the vertebral column. These changes allowed for the upright gait to be overall more energy efficient in comparison to quadrupeds. The evolutionary factors that produced these changes have been the subject of several theories that correspond with environmental changes on a global scale.

Suspensory behaviour is a form of arboreal locomotion or a feeding behavior that involves hanging or suspension of the body below or among tree branches. This behavior enables faster travel while reducing path lengths to cover more ground when travelling, searching for food and avoiding predators. Different types of suspensory behaviour include brachiation, climbing, and bridging. These mechanisms allow larger species to distribute their weight among smaller branches rather than balancing above these weak supports. Primates and sloths are most commonly seen using these behaviours, however, other animals such as bats may be seen hanging below surfaces to obtain food or when resting.

The endurance running hypothesis is a series of conjectures which presume humans evolved anatomical and physiological adaptations to run long distances and, more strongly, that "running is the only known behavior that would account for the different body plans in Homo as opposed to apes or australopithecines".

Ardi (ARA-VP-6/500) is the designation of the fossilized skeletal remains of an Ardipithecus ramidus, thought to be an early human-like female anthropoid 4.4 million years old. It is the most complete early hominid specimen, with most of the skull, teeth, pelvis, hands and feet, more complete than the previously known Australopithecus afarensis specimen called "Lucy". In all, 125 different pieces of fossilized bone were found.

Vertical clinging and leaping (VCL) is a type of arboreal locomotion seen most commonly among the strepsirrhine primates and haplorrhine tarsiers. The animal begins at rest with its torso upright and elbows fixed, with both hands clinging to a vertical support, such as the side of a tree or bamboo stalk. To move from one support to another, it pushes off from one vertical support with its hindlimbs, landing on another vertical support after an extended period of free flight. Vertical clinging and leaping primates have evolved a specialized anatomy to compensate for the physical implications of this form of locomotion. These key morphological specializations have been identified in prosimian fossils from as early as the Eocene.

Danuvius guggenmosi is an extinct species of great ape that lived 11.6 million years ago during the Middle–Late Miocene in southern Germany. It is the sole member of the genus Danuvius. The area at this time was probably a woodland with a seasonal climate. A male specimen was estimated to have weighed about 31 kg (68 lb), and two females 17 and 19 kg. Both genus and species were described in November 2019.

References

  1. Birx, H. (2006). Encyclopedia of Anthropology. Thousand Oaks, California. doi:10.4135/9781412952453. ISBN   9780761930297.{{cite book}}: CS1 maint: location missing publisher (link)
  2. 1 2 Jurmain, Robert; Kilgore, Lynn; Trevathan, Wenda (2008). Essentials of Physical Anthropology (7 ed.). Cengage Learning. pp.  109. ISBN   9780495509394.
  3. 1 2 3 4 Harrison, Terry (2006). "Brachiation". Encyclopedia of Anthropology. Thousand Oaks, CA: SAGE Publications Ltd: Encyclopedia of Anthropology. p. 400. doi:10.4135/9781412952453.n127. ISBN   9780761930297.
  4. Rice, Patricia C.; Moloney, Norah (2005). Biological Anthropology and Prehistory: Exploring our Human Ancestry. Pearson Education, Inc. pp. 178–179, 192. ISBN   978-0-205-38196-8.
  5. D'Août, Kristiaan; Vereecke, Evie E. (2011). Primate Locomotion: Linking in Situ and Ex Situ Research . Springer. pp.  205–206. ISBN   9781441914200.
  6. 1 2 Oka, Kenji; Hirasaki, Eishi; Hirokawa, Yohko; Nakano, Yoshihiko; Kumakura, Hiroo (2010-08-01). "Brief communication: Three-dimensional motion analysis of hindlimb during brachiation in a white-handed gibbon (Hylobates lar)". American Journal of Physical Anthropology. 142 (4): 650–654. doi:10.1002/ajpa.21280. ISSN   1096-8644. PMID   20607695.
  7. 1 2 3 Bertram, John E.A.; Chang, Young-Hui (2001-08-01). "Mechanical energy oscillations of two brachiation gaits: Measurement and simulation". American Journal of Physical Anthropology. 115 (4): 319–326. doi:10.1002/ajpa.1088. ISSN   1096-8644. PMID   11471130.
  8. 1 2 3 4 5 Michilsens, Fana; D'Août, Kristiaan; Aerts, Peter (2011-08-01). "How pendulum-like are siamangs? energy exchange during brachiation". American Journal of Physical Anthropology. 145 (4): 581–591. doi:10.1002/ajpa.21539. ISSN   1096-8644. PMID   21541935.
  9. 1 2 3 4 Fleagle, John (1974). "Dynamics of a brachiating siamang [Hylobates (Symphalangus) syndactylus]". Nature. 248 (5445): 259–260. Bibcode:1974Natur.248..259F. doi:10.1038/248259a0. ISSN   1476-4687. PMID   4819422. S2CID   2060017.
  10. 1 2 Schmidt, Manuela (2006). "Primate Locomotion". Encyclopedia of Anthropology. Thousand Oaks: SAGE Publications, Inc. pp. 1939–1940. doi:10.4135/9781412952453.n734. ISBN   9780761930297.
  11. 1 2 Byron, C.D. (December 2017). "An anatomical and mechanical analysis of the douc monkey (genus Pygathrix), and its role in understanding the evolution of brachiation". American Journal of Physical Anthropology. 164 (4): 801–820. doi:10.1002/ajpa.23320. PMID   29023639.
  12. Fleagle, JG, Stern, JT, Jungers, WL, Susman, RL, Vangor, AK and Wells, JP. (1981). "Climbing: a biomechanical link with brachiation and with bipedalism". Symp. Zool. Soc. Lond. 48: 359-375.
  13. 1 2 Langdon, John H. (2016). The Science of Human Evolution. doi:10.1007/978-3-319-41585-7. ISBN   978-3-319-41584-0. S2CID   7189384.