The Monkey

The Monkey, that animal who similar to human

Monkey is the common name for some animals in the order Primates . The entire order Primates can be divided into two major suborders due to differences in evolutionary levels: the prosimian suborder and the anthropoid suborder. Also known as prosimians and apes. Prosimians refer to some primitive monkeys at a relatively low level of evolution, which are quite different from the monkeys we imagine in terms of appearance and habits. Apes are further divided into monkeys and hominids , the latter of which include gibbons and orangutans at a high level of evolution . Their biggest feature is that they do not have the iconic tails of monkeys, and are more closely related to humans. So, in a narrow sense, monkeys are all species of the primate suborder except for hominids. [2]In fact, in the scientific sense, monkeys are not a strict taxonomic unit. Monkeys are distributed in the Old World (Asia, Africa, and Europe) and the New World (America). This geographical isolation has allowed monkeys in each region to evolve independently.

New World monkeys are classified in the suborder Platyrrhini, while Old World monkeys (superfamily Cercopithecoidea) are part of the suborder Catarrhini , which also includes apes. Old World monkeys are closer to apes than New World monkeys. Chimpanzees , gibbons, and other monkeys are often informally referred to as monkeys, but biologists do not consider them monkeys. Some monkey species have the word “ape” in their names because they have ape-like characteristics.


Molecular evidence suggests that primates originated at the end of the Cretaceous, but this record has not been fully confirmed. Scientists believe that the earliest monkeys or primates should be small squirrel-like animals. Everyone turned their attention to the plesiadapiforms, which were proven to have originated in the Paleocene. However, characteristics such as teeth made people eventually believe that they were not the ancestors of primates, but close relatives of primates, and in some cases they were formally classified as primates. Later studies believed that the truly undisputed primitive primates included omomyids, adapiforms and tasiids . Moreover, the origin of primates is believed to be in Africa and Asia. Many possible primates have been reported in the Paleocene strata on both continents, although the specimens are all teeth and difficult to confirm. 

The oldest confirmed primate or the earliest monkey in the world is Altiatlasius, based on ten isolated cheek teeth and a fragment of a juvenile tooth from the Late Eocene of Morocco. The teeth show similarities to those of simians and primates, but they are more similar to primates, and Altiatlasius has been identified as a proto-mirrorid. It was a small animal, about the size of a modern mouse lemur , weighing only about 50-100 grams



Prosimians (suborder Prosimians) are essentially a type of lower primates. To some extent, they can only be regarded as “half-monkeys” or “near-monkeys”, which means that the degree of evolution of these lower monkeys determines that they are not yet qualified as “full monkeys”. Prosimians appeared as early as the end of the Cretaceous period more than 65 million years ago. They do not have the characteristics of typical primates, and their behavior is also quite different from that of “higher monkeys”. Their brain capacity is small and not as developed as that of higher primates. Generally, apes and monkeys hunt mostly by vision, while prosimians are more guided by their highly sensitive olfactory organs. Therefore, the noses and mouths of prosimians are longer, and the noses are exposed and moist.

Most prosimians have the characteristics of nocturnal animals: they usually have a pair of large eyes that are disproportionate to their heads, and they can see clearly even in the dark night. The reproductive system of prosimians is also different from that of other apes and monkeys. For example, the shape of the uterus and placenta is different, there are at least four nipples, and each litter can produce 2-3 pups. All of these characteristics have led people to mistakenly believe that prosimians are an ancient species that has not “advanced with the times”. In fact, they are a successful group that survived competition and still inhabits a relatively unique habitat. Lemurs, slow lorises, tarsiers, etc. are all members of the prosimian group. 

Monkeys (Suborder Anthropoidea) are higher primates, with more than 300 species in the world. Of these, what we call “true” monkeys account for about 93%, and the remaining 7% are higher apes such as gibbons, orangutans, chimpanzees and gorillas . Currently, monkeys have become the most successful mammals in evolution on Earth. Compared with prosimians, they are larger in size, have shorter snouts, larger brain capacity, more developed limbs and vision, and are more adaptable. Most of them are active during the day, have orderly social groups and activity patterns, have two nipples like humans, and give birth to 1-2 babies per litter. In addition, their various relationships with humans are also closer. 

Based on their distribution and morphology, apes and monkeys can be divided into two major groups: New World monkeys and Old World monkeys . These two groups of monkeys have been separated and evolved independently at least 30 million years ago, which makes them easy to distinguish from the outside: New World monkeys are distributed in Central and South America; their noses are wide and collapsed, with nostrils facing upwards and the left and right nostrils far apart, also known as platyrrhines; these monkeys have long, well-developed tails that curl or have a winding function, such as various marmosets , capuchins , squirrel monkeys , spider monkeys , etc. in South America.

In contrast, Old World monkeys live in the Asian and African continents of the Eastern Hemisphere; most of them have nostrils facing downwards, with a short distance between the left and right nostrils, so they are also called catarrhines; the tails of these monkeys are not winding and are only used to balance the body; various macaques and leaf monkeys in Asia, as well as long-tailed monkeys and baboons

Monkeys are essentially tree dwellers and are skilled arboreal athletes, although some are not as agile as South American monkeys and gibbons. Monkeys owe this ability to the evolution of grasping hands and feet with flat, opposable nails on the thumbs and big toes rather than claws and sensitive touch pads on all toes. 

They have larger brains relative to their body size than all other terrestrial mammals, which means they are larger and smarter, allowing them to cope with the vicissitudes of forest life and social interactions. Monkeys have also evolved advantageous features in vision. Their eyes are generally larger and closer together at the front of the face, with a shortened mouth. Most monkeys have flat faces, which allows them to look forward with a large overlap in the field of view of their two eyes, allowing for stereoscopic vision. Monkeys use their stereoscopic vision to judge distances when leaping from branch to branch. 

Most skulls of monkeys have large cranial cavities and are spherical, which is due to the shortened jaws and flattened faces; the postorbital processes develop into bony eye rings or are completely closed to form eye sockets; most species have short noses, and their sense of smell is inferior to vision, touch and hearing. Some lower species have highly developed olfactory centers in the brain and act largely by smell. Some lemurs have long noses. The nasal bones of 

the golden monkeys and pig-tailed leaf monkeys have degenerated, forming upturned nostrils. The noses of the proboscis monkeys are large and long. These special types are formed by the development of muscles or cartilage. The big toe and other toes of the feet can grasp, making the hands and feet grasping organs. The five fingers of prosimians can only be flexed and extended at the same time, and cannot be used individually. The palm surface is bare, with finger and toe patterns, and the patterns are different. They have very soft or wide foot pads. Most species have flat nails on the tips of the fingers and toes. Generally, the length of the front and rear limbs is not much different.

The tail length of different monkeys varies greatly, ranging from only one protrusion to longer than the body. Most species of the capuchin family have tails that can be used for grasping, and are known as their “fifth hand”. Some Old World monkeys (such as baboons ) have brightly coloured skin on their faces, buttocks or chests, which is particularly noticeable during the breeding season. The buttocks have hard lumps of rough skin called anal calluses. 

Most species have a pair of nipples on the chest or armpits, while the aye-aye has a pair of nipples on the abdomen. The penis of males is pendulous and most have a penis bone, but tarsiers , woolly monkeys , humans and some species do not. The testes are enclosed in a sac. Females have a bicornuate uterus or a single uterus. The body is covered with hair, which can be soft and dense, coarse and hard, or very long in some places, or with different-colored segments on the hair. Some have very long hair on the top of their heads, forming a tufted crown, or very short, flat-topped, or bald. Some have long hair on their cheeks or under the jaw, shaped like a beard . Monkey have long hair on their shoulders, backs, and buttocks. Some have very bright hair.

Living habits

(1) Habitat

Except for some prosimians that are nocturnal, most other monkeys are active during the day. Most monkeys are arboreal animals, but they also move around on the ground. They are very flexible whether they are high up or on the ground. Some monkeys can swim. They usually start looking for food and water in the early morning before people get up. When the weather gets hotter near noon, the monkeys will hide in the shade of trees and hidden places to take a nap. They will continue to move around and eat in the afternoon when the weather gradually cools down. They will prepare for rest before the sun sets. Monkey will also deal with some unexpected dangers and natural enemies during the day, and defend and escape. Species living at high altitudes sometimes have to carry out seasonal group migration.

(2) Food

Most monkeys are omnivorous, feeding mainly on plants. Their choice of food and methods of feeding vary. For example, aye-aye monkeys are good at picking insects out of tree holes or rock crevices. The stomach structure of colobus monkeys is special, and most species eat plant-based foods that are high in crude fiber.

Monkeys eat everything from tree gums and fungi to fruits and leaves, insects, bird eggs, lizards, and even the young of other animals. Different monkeys have different eating habits depending on their habitat and habits: smaller marmosets prefer tree sap and insects; crab- eating macaques living by the sea pick up crabs and other seafood; leaf monkeys and colobus monkeys living in tall, dense rainforests mainly eat leaves; some fierce monkeys will also catch small monkeys and antelope babies.

(3) Growth and reproduction


They reproduce 1-2 times a year, with one baby per litter, and a few may have as many as three. The young grow relatively slowly. During the lactation period, they often cling to the mother’s chest or abdomen or ride on her back, and are carried around by her. Sexually mature females menstruate, and males can mate at any time. Only lower monkeys, such as lemurs, slow lorises , and aye-aye monkeys, have a specific mating and breeding season

Except for a few prosimian monkeys, monkeys generally have a low reproduction rate, usually giving birth to only 1-2 cubs per litter. The cubs stay with their mothers for 3-5 years. The average lifespan of monkeys is only 25-30 years.They reach sexual maturity relatively late, usually at the age of 5-7. Therefore, a female monkey can only raise 3-4 children at most in her lifetime. Low birth rates and high mortality rates often keep the number of wild populations in flux. Once the monkey population decreases sharply. It is difficult to restore it to its original size in a short period of time.

(4) Social Structure

Lower prosimians often live alone, but most monkeys are very social and like to move around in groups. The number of monkeys in a group can range from a few dozen to hundreds. The leader of a group is the monkey king, whose main responsibility is to protect the group’s territory and safety. In monkey society, power is entirely determined by force, and the monkey king is usually the winner of a fight between several young male monkeys. In larger groups, there are also second and third kings.

The monkey king also looks different from other monkeys. It always looks strong, majestic, with soft and shiny fur, and only it can walk with its tail up. Of course, the monkey king’s term of office is not permanent. After a few years of rule, when the “old king” is no longer energetic, the “second king” or other young male monkeys may take his place. The “old king” who fails to “defend his title” is often expelled from the group. The general term of office of the monkey king is 3-4 years. 

The members of the monkey group live together every day. They have the same complex relationship as people, and naturally need to communicate with each other. Although there is no language between them, the combination of facial expressions and sounds is the embodiment of the monkeys’ body language. For example, when a monkey of a lower rank sees a monkey of a higher rank, it usually bares its teeth, makes a sound of submission, and sticks out its buttocks to let the other monkey ride on it, just like a soldier saluting when seeing his superior. When encountering danger, the “guard monkey” on sentry will sound an alarm to notify everyone to evacuate.

When the little monkey is too naughty and disobedient, the monkey father will scare the little monkey into screaming in panic as long as he glares at it… In the zoo, you can often see monkeys grooming their companions, which looks very friendly. In fact, mutual grooming is the most common communication behavior among primates, and it can occur between any monkey regardless of rank. Sometimes during the grooming process, monkeys will put food into their mouths. When it is hot, monkeys will also sweat, and the sweat will form tiny salt grains between the hair. When monkeys need to replenish salt, they will look for these salt grains on themselves or their companions. Over time, this became a habit, and people saw the monkeys searching for salt grains in their fur as if they were catching fleas.

Species value

Primates, also know as monkeys, have many similarities with humans in morphology, physiology, genetics, and evolution, which are unmatched by any other species of animals. These factors are the original motivation for scientists to continue to study them. Research on the changes and development of the ecosystems where monkeys live can provide the necessary basis for similar crises that we humans must face in the future, thereby enriching and deepening the scientific laws in human ecology.

New research on monkey cognitive processes has invaluable reference for understanding the occurrence and evolution of human perception. Research on monkey social behavior is conducive to understanding the origin of certain human behavioral manifestations, and research on their social interaction processes can enrich people’s knowledge of tissue. The results and conclusions of studying the physiological and biochemical characteristics of monkeys have a profound impact on our understanding of human biology and medicine. For example, some drugs, vaccines, and organ transplant experiments are first successfully tested on monkeys before being applied to humans. 

Monkeys have been good helpers in all aspects of human life, not just in scientific research and medical experiments. In one battle, the monkeys were able to wipe out the Japanese pirates by using their unique tactics of sneaking into the enemy camp and setting it on fire. In addition, monkeys, who are naturally smart, can be train to perform various circuses and acrobatics, or work for humans. 

Some organizations train capuchin monkeys to help quadriplegics and other people with severe spinal cord injuries or mobility impairments. First, the monkeys are acclimated to human family life and then receive more training before being send to the patients. In the home, the monkeys help with household chores, such as warming food in the microwave or washing the patient’s face. 

Most monkeys are not very docile, which depends on their species, age and gender. Generally speaking, female monkeys are gentle and can get along well with each other. But male monkeys are very aggressive, and are know as “spoiled monkeys”. Even if they are members of a group, they will often pick fights over trivial matters. When two groups meet, it is more likely that a fight will break out. Most monkeys, especially those that have been domesticated when they were young, are relatively docile and friendly. However, when they grow up, or are abused or have psychological disorders, their personalities usually change. They may even attack humans. Therefore, monkeys are not suitable as pets

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