PRIMATES: CHARACTERISTICS, EVOLUTION, FEEDING, REPRODUCTION - BIOLOGY - 2024

The primates are placental mammals they have, mostly, five fingers on each limb. The thumb is generally opposite the index finger. Their body adaptation means that, although they have four limbs, some species have bipedal locomotion.

The order of primates is represented, among other specimens, by the orangutan, the mandrill, the chimpanzee and man. With the exception of humans, who live in almost all geographical regions, the vast majority of the species in this group inhabit the tropical areas of America, Asia and the African continent.

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Considering the evidence provided by fossils, the oldest primates date back to the late Paleocene period, between 55 and 58 million years ago. Although there are great variations among the members of the order, they share anatomical and functional characteristics that confirm the presence of a common ascendant.

One of these refers to its brain, which compared to body weight is larger than that of other land mammals. In addition, this organ has the Calcarine sulcus, a structure that separates the visual areas of the brain, an aspect that is unique to primates.

They are basically omnivorous animals, although there are carnivorous species and some with a high preference for vegetables. Their diet is closely related to habitat, type of locomotion, anatomy, size and body weight.

Behavior

Socialization

Primates are considered one of the most social animals in the kingdom, being able to form pairs or groups of families, harems with a male or groups where several males live with different females. However, some species, such as the orangutan, are solitary.

Often the female chimpanzees move away from the group where they were born, while the males remain in these, assuming the role of protectors of the group.

There is evidence that this same behavior was practiced in some populations of Australopithecus, where it was found that females, compared to males, used to settle at a greater distance from the place where they were born.

Societies could also be polygynous, where several males coexist with many females, or monogamous, where a male is related to a female, both sharing the raising of the offspring.

Primates often form groups to carry out, together, certain behaviors against the aggressors. The red-tailed monkey works with the blue monkey, to coordinate alert calls between them, in the event that one of them detects the presence of a predator in the area.

Communication

Howler monkey from Guatemala

These animals use olfactory signals to communicate. Primates have an organ called the vomeronasal, whose sensory cells are activated by a chemical stimulus, such as pheromones, used by males to mark the territory.

They can also use vocalizations, gestures, and expressions with their face to express their emotions. These expressions are usually accompanied by gestures with their hands and arms.

Howler monkeys are one of the loudest land mammals, their roars can be heard up to 3 miles away. The investigations associate these calls with the defense of the territory and of the couple.

Construction and use of tools

Primates often build tools. These are used to capture insects or some fish, even for personal hygiene.

In Sumatran orangutans, behaviors have been observed where they take a branch, tear off the leaves and use it to dig holes in trees, in search of termites.

Researchers have recorded events where the chimpanzee takes leaves and moss, making a kind of sponge. They use it to groom themselves and their young.

Evolution

A mammal called Purgatorius, which existed 70 million years ago, in the late Cretaceous, is considered the ancestor of primates. The structure of its teeth and its small size make it similar to today's shrews.

At the beginning of the Cenozoic period, primates were a large group of small animals that lived in the trees. These specialized in nocturnal behaviors, separating to give rise to the first strepsirrinos, predecessors of the current lemurs.

Haplorhines evolved in the late Paleocene and early Eocene. This is evidenced by the existence of the Omomyiformes, ancestors of the tarsians and apes. With the opening of the Atlantic Ocean, the Catarrinos and Platirrinos separate, since they are geographically isolated.

Starting from the Oligopithecus, one of the fossils corresponding to the Oligocene, a separation of the cercopitheci occurred, being the Paropithecus its main representative.

Extinct genera Propliopithecus-Aegiptopithecus

The evolutionary line of these genera, after their specialization and development, gave rise to the hominoids. These, in the Miocene, were radiated in 3 groups: the protogibones (Pliopithecus), the Proconsulidae, ancestors of the hominids, and another extinct group, which developed brachiation.

A group of hominoids, descendants of Proconsul, spread to Europe, Asia and Africa. For some researchers, these were divided into the Driopithecines and the Ramapithecines, which include the fossils of Ramapithecus, Kenyapithecus and Sivapithecus.

Driopithecus and Ramapithecus are currently considered to have no evolutionary descent, being specimens from Europe and Asia. On the other hand, the Sivapithecus is the ancestor of the orangutans.

Kenvapithecus is designated as the ancestor of hominids, gorilla and chimpanzee. At the end of the Miocene there is a void of fossilized remains, which makes it difficult to specify details about the appearance of hominids.

There is only one molar from Lukeino, a portion of the jaw from Lothagam, a temporal bone from Chemeron and the humerus from Kanapoi, all these fossils correspond to the hominid.

Taxonomy

• Animalia Kingdom.
• Sub-kingdom: Bilateria,
• Infra-realm: Deuterostomy.
• Phylum: Chordates.
• Sub-phylum: Vertebrates.
• Infrafilum: Gnathostomata.
• Superclass: Tetrapoda.
• Class: Mammal.
• Sub-class: Theria.
• Infra-class: Eutheria.

Order Primates

Suborder Strepsirrhini

The brain has large olfactory lobes and a vomeronasal organ, which helps to efficiently capture chemical stimuli, such as pheromones.

Your eyes have a reflective layer of riblifavin crystals, called tapetum lucidum, which improves your night vision. The eye sockets have an ossified ring, formed by the junction between the frontal and zygomatic bone.

His vision is stereoscopic, because his eyes point forward. Some species have large ears and the ability to move them.

The inherent characteristics of the ankle bones allow members of this suborder to perform complex rotations of the foot, which are usually inverted or slightly turned inward.

These are divided into the suborders Adapiformes, whose species are now extinct, and Lemuriformes, represented by the ring-tailed lemur, the gigantic lazy lemur, and the Madagascar lemur.

Suborder Haplorrhini

They are diurnal animals, whose females have the uterus with a single chamber, with the exception of the tarsiers that have it of the bicornuate type. They generally have only one calf in each gestation.

The body can be medium to large in size. The sense of vision is developed, being able to distinguish the colors of objects. Her upper lip is not connected to her nose or gums, making it easier for her to perform various facial expressions.

The nostrils can be found to the sides, as is the case with capuchin monkeys, or pointing to the front, as they are present in the macaque.

The Haplorrhini are subdivided into two infra-orders: the Simiiformes and the Tarsiiformes, known as tarsios or tarsiers, being the phantom tarsier (Tarsius tarsier) one of their representatives.

Some of the species that make up the Simiiformes group are: man, the capuchin monkey, howler monkeys, gorilla, chimpanzee and orangutans.

Source: pixabay.com redesigned by Johanna Caraballo

General characteristics

-Size

Its size can have significant variations, due to the diversity of specimens that make up this group. Thus, Madame Berthe's mouse lemur weighs 30 grams, counteracting the more than 200 kilograms that the eastern gorilla could weigh.

-Senses

The brain is enlarged in the areas related to vision and touch, the occipital and parietal lobes respectively. In higher primates this gives the brain a characteristic shape, compared to that of the rest of the members of the order.

Touch

The touch receptors, Meisser's corpuscles, although present in all primates, are more highly developed in monkeys and humans. The skin that covers the hand and feet has structures adapted for tactile discrimination.

An example of this is fingerprints, which are finely grooved corrugations of the skin, and the absence of foot pads.

View

Almost all primates have color vision except South American durukulis and tarsiers. Their eyes are oriented forward, allowing them to have a binocular vision that facilitates them to have a more precise perception of the distance of objects.

-Face

The muzzle is reduced, possibly related to some aspects such as the existence of a less complex nasal shell, high innervation of the olfactory membrane and sensitivity at the distal end of the nose. This implies a decrease in the primacy of the olfactory sense, especially in higher primates.

-Locomotion

Jumps

In these animals it can occur in two ways: parabolic upwards (lemurs and galagos) and horizontally, along and outwards, falling downwards.

The primates that practice this model of locomotion have elongated legs and huge quadriceps muscles, to have the necessary strength in the extension of the leg.

Climbing

This is a very old arboreal adaptation. Although it is not very common in primates, several species are capable of climbing substrates vertically. This type of locomotion allows them to climb trees, using their long forelimbs.

Climbing can be divided into climbing, which consists of an oblique type of movement leaning on small objects, and vertical climbing, which allows them to vertically raise and lower a surface.

Quadripedalism

It is one of those used by most non-human primates. It can be arboreal and terrestrial. The animals practice it thanks to the fact that both limbs have similar lengths and that they shift part of the center of gravity towards the branch, flexing their elbows and knees.

Those who walk on the ground, on their four limbs, can be digitigrade, dividing into those who do it with their knuckles and those with a standing fist.

Brachiation

Apes and spider monkeys move using swing arm or hanging arm movements. The characteristics of the elbow joint allow them to execute great extension and flexion movements.

In addition, their long hooked fingers help them to balance during the great jumps they make between tree and tree.

Bipeds

In this type of locomotion, typical of man and eventually carried out by gorillas, primates get up and move using their two hind limbs.

Feeding

Food is a very important factor in the ecology of primates, playing a fundamental role in their dispersal and adaptation, as well as in the development of the organs of the digestive system, especially the teeth and jaw.

The vast majority of primates are omnivores. However, there is a carnivorous species, the tarsier, which includes insects, crustaceans, lizards and snakes in its diet. Gelatos and lemurs feed preferentially on herbs, eating their seeds, roots, fruits and stems.

To obtain meat, humans can hunt their prey or consume those they have domesticated. Nonhuman primates may consume other species of primates, which they occasionally do with self-made tools.

Chimpanzees sharpen sticks, breaking them at one or both ends. They then use their teeth to make the points spear-shaped. They are often introduced into the hollows of trees to capture the young of small primates, to be consumed. Although they don't always achieve the goal, they are quite persistent.

Anatomical specializations

The organism of primates has had anatomical adaptations that allow them to obtain and process the food they eat. For example, howler monkeys, which eat leaves, have a long digestive tract so that they can more easily absorb the nutrients they contain.

The marmoset eats gum, an exudate from trees that contains sap. The animal uses its claws to hold onto the trunk, using incisor teeth to open the bark of the trees and to grab its food.

Madagascar inhabits the Aye aye, a small primate endemic to that place. It taps trees to find insect larvae. Once he finds them, he gnaws on the bark with his incisors. Then insert the middle finger, which is longer than the others, to extract the larvae.

Primates have behaviors where their intelligence is revealed. Such is the case of the black striped cappuccino, which could be observed breaking the nuts by hitting them with a stone.

Reproduction

The functions of the reproductive organs are very similar among primates. However, there are some variations in the male and female external genitalia, which constitutes a natural barrier to prevent mating between different species.

Male reproductive organs

The penis, as an external reproductive organ, is pendular, hanging freely. This is a remarkable difference from most other mammals.

In some primates, except for modern humans, tarsiers, and several South American monkeys, the penis has a small bone called the baculum. This is directly related to the erection of the same.

The testes are usually found, in various species, permanently in the scrotum. On the other hand, in humans these organs migrate from the intra-abdominal cavity before birth. In the rest of the primates, this migration occurs after birth.

External variation during reproductive time is evident in some males, as their testicles swell and the scrotum changes color.

Female sexual organs

The ovaries produce and release the eggs, which travel through the oviducts to the uterus. In primates this organ may have two horns (bicornuate) or have a single chamber. While in mammals there is a urovagina junction, in primates the vagina and urethra have separate external outlets.

In addition, they have a vagina and externally the labia majora and minora. These cover and protect the vaginal opening and clitoris. In a large number of primates, the clitoris has a small bone called the baubellum.

In females, the vulva can swell and change color, announcing the proximity of the ovulation period.

During gestation the placenta and umbilical cord are formed. Both are transitory organs involved in the supply of nutrients and oxygen to the fetus.

Reproductive process

This occurs in four moments: copulation, gestation, delivery or birth and lactation. The breeding seasons are separated by stages of anestrus, where in some primates such as mouse lemurs (Microcebus), the vagina closes.

Environmental factors could influence the reproductive season. In Galago senegalensis, estrus occurs in December and August, while natal Madagascar reproduces in the fall. Monkeys and humans have continuous type cycles throughout the year.

Anatomy and morphology

Nervous system

The nervous system in primates is divided into central and peripheral. The central one is made up of the brain and the spinal cord. The peripheral nervous system is made up of the cranial and spinal nerves and their branches.

The central nervous system is specialized. This allows you to capture and interpret the different stimuli coming from the environment that surrounds them. It has areas of association that provide connections between the motor and sensory cortex of the brain.

In these areas there are memory banks where past experiences are stored, which are used to face situations.

Brain

The neocortex is considered as the brain area responsible for the ability to reason. In higher primates, they have the function of capturing the different inputs from the receptors of sight, taste, hearing and smell and converting them into responses.

The large size of the human brain is not related to the number of neurons, but to their much larger size and the complexity of the connections between them. The skull protects the brain. The endocranial volume in humans is almost three times greater than in other primates.

Teeth

Primates are heterodonts, so they have several types of teeth: canines, incisors, pre-molars, and molars.

The incisors vary considerably. In some species, such as the fork-crowned lemur, they form the well-known “tooth combs”. These consist of a group of incisors and canines located in the lower jaw. These teeth have the peculiarity of being long, flat and somewhat curved.

Canines are present in all primates, with certain variations in their size, shape, and function. They are used primarily to defend against aggressors and to maintain social order within the group.

Generally in males they are larger than in females, with the exception of humans where both sexes are of equal size.

Skeleton

Nonhuman primates have broad ribs and a shorter spine, with reduced sacral and caudal vertebrae. The tail may have been lost, as in gibbons, great apes, and humans.

They all have clavicles, and the radius and ulna bones are separate, as are the tibia and fibula. The exception to this is the tarsier, whose fibula is fused with the tibia.

The spinal column has an "anticline" vertebra located in the upper back. This is characteristic in all quadrupeds, except in monkeys that have a semi-straight posture.

Hands and feet

The spider monkeys and colobus monkeys in Africa do not have a thumb or it is reduced. The rest of the primates are pentadactyl, with 5 toes on each limb. The thumbs are opposites, this being a more developed characteristic in humans.

All members of this group, to varying degrees, have grasping hands and grasping feet, except in the case of humans.

Habitat

Some specimens live partially on land, spending long periods of time in trees. Others are terrestrial, like gelates and humans.

The white-faced capuchin lives on the branches of trees, where they rest and are kept safe from predators. In the daytime, they come down to earth in search of their food

Most non-human species live in the humid tropical forests of Africa, India, Southeast Asia, and South America. Others, like the Japanese macaque, live in the Hoshü Mountains (Japan), where there is snow most of the year.

Although in most habitats there are no lakes or rivers, primates tend to be good swimmers. The strepsirrhini live on the island of Madagascar, considered a natural reserve of this group.

On the other hand, the haplorines, inhabit Africa, Asia and America, including the north of Mexico. Some members of this species live in Europe, not being considered as their natural habitat, since in 1704 man brought them to that continent.

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