The Evolution in Primate Locomotion and Body Configuration

1 January 2017

The Evolution in Primate Locomotion and Body Configuration Calista Lee Anthropology 115 The Evolution of Primate Locomotion and Body Configuration Primates first evolved from the trees of tropical forests, later to the ground. Through the times of promisians to human, many characteristics has been represented due to the adaptations to new environments and resulted in evolutionary changes. The Earth has encountered several geological and climatic changes over time. For the primates existed at that time had to adjust itself especially in body configurations and locomotion in order to better survive.

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It is important to be aware of this information since we are the part of occurring changes as well. Throughout the evolution owing to the transforming environments interacting with natural selection, primates developed their own ways to move better (meaning changes in locomotion) with different types of bodies (meaning changes in body configuration). Grade I – Lemuroids Lemuroids, including true lemurs, lorises and galagos are the most primitive ones among the living primates. As they are the first grade of primates, they evolved in about 65 million years ago, in Paleocene epoch.

Lemurs and lorises are the most primitive because they are more close to ancestral traits such as their reliance on olfaction, which enhances the sense of smell. Having dental comb, which formed by forward-projecting lower incisors and canines for feeding and grooming and grooming claw on the second toe are some distinguishable identities. Lemurs are only found on Madagascar and its adjacent islands. They vary in numerous species and ecological niches since they have no competition from monkeys and apes on the islands they live in. Lemurs range in size from the smallest mouse lemur with 5 inches to the indri with 2 to 3 feet (Nowak, 1999).

The size of the lemur in comparison to other primates is an adaptation to the limited space on the island where it evolved (Jennifer, 2011). Locomotion of lemurs is diversified. Some are arboreal primarily and others are terrestrial like ring-tailed lemurs with their long, striped tails. It is common that some arboreal species are quadrupeds, and others (indris, ring-tails, and sifakas) are vertical clingers and leapers. Vertical clinging and leaping are the special characteristic of some lemurs and tarsiers. Lemurs are skillful climbers with strong hands and feet.

Their hindlimbs are muscular to aid jumping from trees to trees. In midair to grab branches, they can twist their bodies at different angles. Since lemurs are adapted to climbing and jumping, many lemurs cannot walk up right. The sifaka lemur hops sideways on its back legs to overcome its inability to walk bipedally (Jennifer, 2011). Lorises are mostly found in tropical forests and woodlands of India, Sri Lanka, Southeast Asia and Africa. They somehow resemble lemurs, but they survived in mainland by adapting to nocturnal activity. They are slow and careful which contributes to the challenges of their predators to find lorises.

Their forelimbs and hindlimbs are more similar in length and they lack long tails. The tail, which looks like thick fur is variety of colors. They are arboreal and use slow quadrupedalism that enables them to climb the trees. They also have flexible joints that allow suspension by hindlimbs while the hands are used in feeding (Fleagle, 1999). The size can vary on the species, ages. Adult lorises usually are in size of 15 inches and weigh up to 4. 4 pounds. Lorises have a powerful grasp that makes it difficult to remove them from branches, even though they are slow.

Galagos are in the same general category with lorises due to their exhibitions of good grasping, climbing abilities and visual apparatus. Also called bush baby which was created by their cries or appearance, they evolved in the forested and woodland savanna areas of sub-Saharan Africa. They range in size from the size of the mouse to a small cat. Unlike lorises, however, they are nimble vertical clingers and leapers. They have large eyes that give them extraordinary night vision, developed strong hindlimbs, have acute hearing, and possesses long furred tails that help them with their balance (MacDonald, 2006).

They have nails in all digits except for the grooming claw on the second toe. Their arms tend to be shorter than their legs, and they have strong hind legs for jumping, storing the elastic energy, which allows them to jump up to 6. 6 feet. Figure I. Galago showing its hands that grasp on the branch tight. Grade II – Tarsiers The second grade of primates evolved about 53 million years ago, in Eocene epoch. There are five tarsier species that all live in the islands of Southeast Asia, where they inhabit from tropical forest to backyard gardens (Jurmain, et al, 2011).

They are considered to be closely related to lemurs and lorises (prosimian family) for the several traits that they share with Grade I primates while having some anthropoid features as well. However, tarsiers have distinctive characteristics that isolate them from other primates. They are categorized as the smallest creatures among the primate species and they are well known for their enormous eyes which is as large as its brain. They are normally nocturnal insectivores but sometimes carnivorous. They catch insects by jumping at them and as they jump from tree to tree, they even hunt for birds while in motion.

The body size grows from 4 inches to 6 inches. Being one of the smallest primates, they comparatively have large hands and feet that reflects both clinging abilities and predatory habits of tarsiers (Fleagle, 1999). The fingers are elongated with the third finger much longer than others (about the length of the upper arm). Most digits have nails but they have grooming claws on their second and third fingers. Their feet have particularly elongated tarsal bones (ankle region), which the name of the animal is derived from. They move up to vertical surfaces due to their hands that acts like suction cups and are padded.

Except for the hands and tail, the body is covered with hair. They have a thin tail that is about 7. 5 to 10 inches long and is mostly furless except there are small amount of hair at the end. They use their tails to balance themselves. Their fur is very soft and velvety and usually ocher or beige in color. Figure II. Tarsier clinging vertically on the tree branch with its hands and feet. They are vertical clingers and jumpers and they use this characteristic to surprise their prey. The hindlimbs are longer, usually as twice as much, and that enables them to leap well.

They move from tree to tree by clinging vertically to a trunk or branch and then leaping to cling vertically to the next trunk or branch (Fleagle, 1999). They are known to able to jump up to seven feet. In order to leap effectively and easily, the lower leg bones are fused about halfway down their length, giving the leg more strength (“Tarsiers – Locomotion,” n. d. ). They hop on their long legs when not moving from branch to branch. Grade III – Monkeys The third grade of primates, monkeys, evolved about 35 million years ago in Oligocene epoch.

Though there are variations among anthropoids, they share certain characteristics that distinguish them from prosimian groups such as a larger average body size (Jurmain, et al, 2011). They are divided into two groups, New and Old World monkeys by geographical area (as well as their separate evolutionary history) and several differences (that may have derived from the different habitat) in characteristics such as the shape of their noses and the type of tails. The noses of New World monkeys are flatter and broader with outward-facing nostrils whereas Old World monkeys have narrower noses with downward-facing nostrils.

Also New World monkeys are the only ones with prehensile tails while in comparison Old World monkeys have shorter, non-grasping tails. Along the same way, although they are grouped together as monkeys for appropriate reasons, Old World monkeys are related more closely to hominoids than to New World monkeys, proving that they are not a unitary group. Figure III. Female black howler monkey with its prehensile tail. New world monkeys consist of approximately 70 species. They occur widely in arboreal environments in Central, South America and southern Mexico throughout the forested areas.

They live exclusively on the trees and some never even touch the ground. They range in size from small (pygmy marmoset which is 5. 5 to 6. 3 inches and weighs 4. 2 to 6. 7 oz) to mid-sized (howler monkey which weighs 20 pounds and southern muriqui that weighs up to 33 pounds). Most of New World monkeys are quadrupedal except some, such as spider monkeys, are semibrachiators that use their arms and tail to swing through the trees. As spider monkeys swing and move from trees to trees, they grip the branch with their hands. Marmosets and tamarins, the smallest within the group, have claws instead of nails and use them for climbing.

Other species, such as howlers, spider monkeys and muriquis, have prehensile tails for locomotion and hanging from tree branches (Jurmain, et al, 2011). Overall, they have relatively short forearm and most lack opposable thumbs. They usually have prehensile tails, which act as a fifth thumb. They vary in wide range of locomotor abilities: leaping, arboreal quadrupedalism and suspensory postures used by larger species (Fleagle, 1999). Old World monkeys inhabit in sub-Saharan Africa and southern Asia throughout tropical jungle to semiarid desert and even in northern Japan where it is seasonally snow-covered.

They are the most distributed primates except humans. They include many familiar species of primates such as macaques, baboons, colobus monkey, langur and mandrills. They vary in size from medium to large. The smallest known is the talapoin with the body length of 13 to 14. 5 inches and weight of 1. 5 to 3 pounds whereas the largest is male mandrill about 27. 5 inches of body length and 110 pounds in weight. Most are adapted to arboreal and quadrupedal lives but they do range in primary locomotion. Guenons, macaques, and langurs are adapted to arboreal quadrupedalism.

Baboons and some other types of macaques are terrestrial quadrupedal while colobus monkeys use semibrachiation and acrobatic leaping (Jurmain, et al, 2011). In general, they have long thumbs and short fingers. Also their forelimbs and hindlimbs tend to be in similar size while having long trucks. They have non-prehensile tails but some species like colobus monkeys use their long tails to balance. Grade IV – Apes and Men The fourth grade of the primates, hominoids (which include apes and men), started 25 million years ago in Miocene epoch. This grade contains gibbons and siamangs, orangutans, gorillas, chimpanzees, bonobos and humans.

They differ from monkeys in various ways: larger body size in general, shorter and more stable trunk, no tail and more complex behavior to name a few. Also they are more adapted to the life on ground than monkeys. Apes are native in Africa and Asia. “Gibbons and siamangs live in Southeast Asia and two orangutan subspecies live on the islands of Borneo and Sumatra. In Africa, until the mid- to late twentieth century, gorillas chimpanzees, and bonobos occupied the forested areas of western central, and eastern Africa, but their habitat is now extremely fragmented, and all are now threatened or highly endangered” (Jurmain, et al, 2011, p. 66). Gibbons and siamangs are the smallest among the apes. Gibbons have long and thin bodies that usually weigh about 13 pounds and largest siamangs with 25 pounds. Their distinctive locomotion is the brachiation with their long arms and they can jump up to 50 ft for this feature. But they can also leap (up to 26 ft) and walk bipedally with arms raised for balance. They have long, curved and slender digits on hands and feet with shorter thumb which help them to grab onto branches easily when they brachiate. Also their shoulder muscle is developed due to their locomotion.

Their fur is generally gray, black or brown, often with white marks on face, feet and hands. Orangutans are the largest Asian ape. They are slow and careful climbers that use all four limbs to grasp and support. They sometimes move quadrupedally on the ground though they are arboreal (Jurmain, et al, 2011). They have a short pollex, hook like hands with long curved fingers and very long forelimbs. Also their hindlimbs are very mobile due to the short, hand like feet with long, curved digits and a reduced hallux. Curved fingers and toes and opposable thumb and toe allow them to grasp tight on things easily.

Females and immature orangutans tend to be totally arboreal while adult males move around by slow quadrumanous climbing which they use hands and feet interchangeably as they move and transfer themselves from tree to free. Their hands held in a fist they walk quadrupedally on the ground (Fleagle, 1999). They are large and bulky. Males are large which can weigh more than 200 pounds whereas females weigh no more than 100 pounds. The body is mostly covered with long reddish-brown hair on grey-black skin. Some males can grow some hair like moustache.

Gorillas are the largest species of living primates. Adult males can weigh up to 400 pounds and females, usually half of the size of silverback, weigh around 150 to 200 pounds. They are most famous for their knuckle-walking which is included in terrestrial quadrupedalism. But they sometimes walk bipedally for short distances for carrying food or defending themselves. They have relatively long forelimbs and short truck which is a result from adaption for knuckle-walking. Their hands are broad and have large pollex. They rarely climb trees which mean they mostly rest on the ground (Fleagle, 1999).

Chimpanzees are considered to be the closest living relative to humans for their communication, appearance and bone structure. They share similar limp proportions and upper body shape with gorillas. Male can weigh up to 150 pounds and grow up to 5. 6 feet whereas females tend to be smaller. When on the ground they walk quadrupedally and do knuckle-walking. Also they sometimes walk bipedally for short distances to carry objects. However, they spend more time in the trees using brachiation. Bonobos, previously called pygmy chimpanzees, are slightly more gracile than chimpanzees.

They have slender upper body, thin neck, narrow shoulders, and legs that are relatively longer than arms. On ground they use quadrupedal knuckle-walking and bipedal walking occurs rarely. It can be said that bonobos are more arboreal than chimpanzees. Humans are upright, bipedal primates habitually. They have relatively short truck and long arms than other primates. The hands consist of short and slender fingers and opposable thumb for easy grasp. The hallux is aligned with other toes which is adapted to bipedal walking patterns. They have flexible limbs and grasping hands that indicate their primate, arboreal past.

Humans in current time has lost noticeable amount of hair which covered almost the entire body before. When compared with other species, humans have a highly developed brain capable of abstract reasoning, language, and introspection. This mental capability, combined with an erect body carriage that frees their upper limbs for manipulating objects, has allowed humans to make a far greater use of tools than any other species (Fleagle, 1999). Humans are the only species that write, think, depend on culture, have desire to learn and create complex social structures. Figure IV. Showing the link between ape and man.

It is evident that humans have evolved from primates. Especially when I visited Los Angeles Zoo after seeing the different kinds of primates it became clearer. The behaviors and even appearances of several primates were similar to that of humans. The most amazing and memorable experience was to see the chimpanzees. They seemed to be in a society, just like ours with expressions and hierarchies. Knowing where we came from and understanding evolution is important because not only is it the starting point of our species, but also the first step of all the other species that reside with us in this planet.

Since the time of prosimians until now, many environmental changes and natural selection occurred which transformed the world that the primates lived in. In order to survive, primates, on each grade, gradually created their own developments in body configuration and traveling position from arboreal to bipedal. The locomotion of primates have shifted successfully adapting their bodies suitable to remain alive due to the natural selection that interacted with environmental factors. References Alemseged, Z. , Coppens, Y. , & Geraads, D. (2002) Hominid cranium from Omo: description and taxonomy of Omo-323-1976-896.

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