Brachiation

, they retain several adaptations that allow them to use brachiation, as demonstrated here with a group of U.S. Marines using monkey bars. 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. 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. 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. Ricochetal brachiation uses an exchange of translational and rotational kinetic energy to move forward, and is compared to a "whip-like" motion. Due to its aerial phase, ricochetal brachiation is similar to bipedal running in humans. == Models of brachiation ==

Pendulum movement Continuous contact brachiation has often been compared to the movement of a simple pendulum. The use of gravitational acceleration to effect movement can be found in both the brachiating primate and the moving ball in a pendulum model. 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. Brachiating primates have adapted these three strategies for maximizing forward movement by adjusting its posture during each swing. The amount of energy transferred from potential to kinetic during pendulum-like movement is known as energy recovery. 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. 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. ==Evolution of brachiation==

Brachiation originated in Africa, thirteen million years ago. 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. This would explain why living apes and humans share many unusual morphological aspects of the upper limb and thorax. Specialized suspensory behaviour was shown to have evolved independently between hominid groups. 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. ==See also==