Evolution: Taxonomy, Primate Physiology

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Table of Contents

Taxonomy
Primate Physiology
Comparative Anatomy
Technology and Intelligence
Work Cited

Taxonomy

Homologies are traits evident in two or more than two organisms that were inherited from a common ancestor. Taxonomy looks at the similarities present in an organism to determine a common ancestor. The similarities can be exhibited in the physical characteristics, genes, the functionality of the various structures present. The structures that fall into the same lineage of ancestry are known as homologous structures.

A dolphins flipper, human arm, cat arm, and bats feathers are homologies. While human beings have a humerus, ulnar, radius, carpals, metacarpals, and phalanges, this structure appears in similar organisms such as bats, whales, and other mammals. This denotes that these organisms have the same ancestors. The tailbone in human beings and the monkeys tails are homologies, except that the tail in humans is a vestigial structure. This denotes that they evolved from one ancestor with a tail.

Furthermore, all primates share the same vertebrate erection; for instance, whales and tiny human beings have an equal number of bones of the vertebrae with a giant giraffe. The structure of the bones is the same in all the above-stated organisms. Additionally, cats, human beings, and dogs have the same pelvis structure and are homologies to a vestigial pair in snakes. The bones in the snake are the last remaining parts of the pelvis though the snakes bones however, the snake does not have bones. Evidence has shown that the organisms classification into the same group based on the traits has not yielded positive results in the tracing of the ancestry or the origin (Boe et al. 128). This has brought a challenge in trying to classify the homologies into the same characteristics. There are also discrepancies between the organ and character that make it impossible to classify the organisms.

The remarkable similarity is only referred to as part of the homology. In cladistics, determining whether an organism is homologous and therefore comparable to another is a question of the organisms transformation condition. Homoplasy an error in the homology assignment. The type that occurs is more related to phylogenetics, making phylogenetics more difficult in the analysis. Construction of the tree when there is homoplasy occlusion can be challenging, especially in the analysis part.

The primates are recognized to have taxa classification similar to those of clades. There are two recognized orders, including Strepsirrhini and haplorrhine. The former are lorises and lemurs, while the latter include apes, humans, and monkeys. These two orders differ in the structure of the mouth, placenta, and nose. The strepsirrhines have a moist and bare muzzle and have a reflective layer behind the retina known as tapetum lucidum. In contrast, the haplorrhines such as monkeys have a hairy muzzle and less wet, and do not have a tapetum. Instead, they have fovea.

The uterine wall of strepsirrhines does not have preparation during pregnancy. Unlike the haplorrhines that have to be vascularized every month, they do not menstruate, and menstruation occurs have no uterine; the orders are then divided into infraorders. The strepsirrhines are divided into Lemuriformes and lorisiformes, while the haplorrhines are divided into simiiformes and tasiiformes (Boe et al. 219). The former is divided into catarrhine, platyrrhine, and tarsiers. The latter is the new world monkey while the former old-world monkeys.

Primate Physiology

All primates have prehensile feet and hands, and most of them have five digits inclusive of the opposable thumb. The primates hands and feet can perform different activities such as gripping, grabbing, climbing trees, and holding onto branches. Humans are exceptional since their feet are not prehensible but rather pentadactyl. The hands of humans are sensitive compared to other primates. Same as the other features that define primates, these features add their ability to live successfully live-in tress and perform other characteristics.

The shoulder and the hips joints of the primates are flexible and limber, unlike other mammals. The shoulder helps them to swing over trees, and the hip joint increases the range of motion; these features assist the primates in their arbor-able lifestyles. The brain of primates is highly distinguishable from other primates. The olfactory area is reduced, and the cerebrum is augmented to increase sight and social behavior. Other features include the presence of a nail at the fingertips, but other mammals have claws. Primate has collarbone and can erect, which is even visible in quadruples. Most species of primates have bipedalism. Moreover, the primates have one offspring per pregnancy, and they possess the adaptation of climbing trees since they are descended from tree-dwellers.

Streprrhinis have a nose that is moist and have muzzles for example the bush babies and the dogs. Their noses secret much mucus and add onto the moist by frequently licking their nose using their tongue. This allows cooling and evaporation and also contributes to their sense of smell. On the other hand, haplorrhines have a dry nose that is covered by downy hair and does not have a muzzle. The hairy nose prevents the entry of impurities. There is a reflective layer known as tapetum lucidum found in strepsirrhines behind the retina, which increases surface area for light at night, hence enabling night vision (Boe et al. 222). Haplorrhines have no tapetum; they instead have a fovea that enhances vision. However, not all strepsirrhines are nocturnal, and not all haplorrhines are diurnal. Haplorrhines have a highly vascularized uterus that undergoes preparation for pregnancy every month, and when there is no fertilization, the wall is shed in the form of menstruation. They have a hemochorial placenta, while the strepsirrhines have an epitheliochorial placenta, they do not undergo pregnancy preparation, and they do not menstruate.

Catarrhines have a narrow nose, forward-facing, and the nostrils separated by the nasal septum, while the platyrrhines have a flattened nose. The catarrhines have a more oversized cerebrum for sight and social behavior, while the platyrrhines have a smaller cerebrum. Catarrhines have a hypothalamic-pituitary-gonadal axis regulating gonadal hormone production, while platyrrhines do not have such an axis. In platyrrhines, the presence of androgens is involved with the social ranking and behavior and less involved in reproduction based on cells. Platyrrhines reach sexual maturation after a short period of typical life expectancy of more than a decade compared to catarrhines that take time before reaching sexual maturity. Platyrrhine, due to its increased life expectancy, is preferred for clinical studies compared to catarrhines.

Comparative Anatomy

Orthograde posture means walking straight or upright, the limbs do not move in parallel, while in pronograde stance, the limbs move in parallel to one another while waking. The scapula is dorsally placed for orthograde mammals, while for the pronograde primates, the scapula is shorter. The length to width of the scapula, also known as scapula index, is decreased in upright primates, while in quadruple mammals, the scapula is longer and less broad; therefore, the index is increased. The ribcage of bipedal organisms is flattened, and the acromion process of the scapula is extensive. Simultaneously, in quadruple, the rib cage is uneven, and the acromion process is more diminutive. This is because there is a need for more use of deltoid muscles due to hands freeing.

The hands of quadruple animals are long curved and less opposable thump than the orthograde that has shortened and more muscular and fully opposable thump. The orthograde have complete grip precision due to the firm hands and fully opposable thumbs compared to the pronograde. The ancestor of bipedal organisms was a tree dweller animal that could walk quadrupedally between one branch of the tree. From the ancestor, the two trends of locomotion were obtained. One which led to the gorillas elongation of the forelimbs so that their lengthened limbs knuckles can support the animal when walking. The second trend consisted of shortening of the trunk, relocation of the shoulders blades, and increased emphasis on the trunk erection and growth in the hind limbs support. This trend led to the achievement of bipedalism.

The hand gripping and the tool behavior can explain the opposable thumps. There are various reasons to support that the foot selection was the last compared to the selection of the hands that led to grip precision. The hallux selection was much more robust, and the selection of the lateral toes followed it. The changes in the feet happened after the hands were selected to precision grip. Scientists have shown that the early ancestors used to walk quadrupedally and still used their feet to hold onto the branches of a tree, they walked differently on the ground (Boe et al. 248). The big toe evolved due to the push-off power during walking and learning.

Hence, the big toe was the last to grow because it was the last to change. After all, mankinds ancestors lived mostly on trees, and the feet were used for grabbing the trees. Moreover, due to the hypothesis that bipedal movement evolved due to the stone age period, this freed the hands to carry tools. This is evidence that the precise grip happened first that made it possible for throwing, clubbing, and holding tools, then the big toe (Boe et al. 208).

The three structures of the brain consisting of the cerebrum, cerebellum, and brain stem. The cerebrum is the most significant part of the brain that carries around 85% of the brains total weight, and it has frontal, parietal, occipital, and temporal areas. It is the last part of the brain to evolve and controls all voluntary activities, such as emotions, intelligence, communication, and creativity. The cerebellum is the part of the brain underneath the cerebrum, and it is the first part of the brain to evolve. It takes around 10% of the total weight of the brain (Boe et al. 204). However, around half of the brain neurons are located in the cerebellum. It is responsible for posture, balance, cognitive functions, muscle tone, and coordination. The brainstem is located underneath the cerebrum and the cerebellum. It connects the rest of the brain to the spinal cord. It accounts for 5% of the brain and is also the oldest to evolve. It controls the sleep-wake cycle, regulates the lungs and the heart, coordinates the brain and the peripheral nervous system, and controls reflexes.

The olfactory centers dominate the cerebrum of most mammals. In primates, the sense of smell is less critical and more visual areas in the brain. Due to the use-disuse rule, primates did not use a sense of smell more than a sense of vision, which led to the enlargement of the occipital lobes responsible for fiction and the parietal lobes accountable for touch. The shape of the brain has the same features throughout the primates. In strepsirrhines, the two bony orbits are 140 degrees apart, while in haplorrhines, the angle is 20 degrees (Boe et al. 203). Moreover, due to the large size of the brain of haplorrhines, there is an elaboration of the visual and tactile senses.

Technology and Intelligence

Language is a fundamental element in evolution, and the what people say have their emotions. Language shapes the ongoing experiences and perceptions. The use of emotional words such as anger and disgust to label some posed facial expressions reduces the brain areas activity associated with uncertainty, such as the amygdala. When one expresses a particular emotion using language, the children will register that in the brain, and whenever they have the same feelings, they will communicate the same registered emotions.

The language supports the conceptual knowledge used in the emotions.

The language supports the conceptual knowledge used in the emotions. Language helps humans to acquire abstract concepts. Humans make meaning of the ongoing sensory perceptions through language. Psychological constructivist feelings state that language is a glue for knowledge, critical concepts and shapes sensory perceptions continuous processes. The essential elements of the mind that make language necessary are the representations of the sensations inside the body, and the knowledge concepts are used to make these sensations meaningful.

Language has a critical role in memory. For example, one is likely to remember childhood memory when others like the language they spoke. It acts as a hook to draw and resurface memories. The thoughts and feelings are dependent on the knowledge people have. There is a link between language and memory in the hippocampus since the hippocampus relates the incoming words to the brain via semantic knowledge, generates meaning, and stores them as what is known as semantic memory. Episodic memory is dependent on language since it is built on past experiences and events. Displacement is the capability of referring to small and spatial objects during communication. It is one of the critical features of human language. This ability is not direct and is unique to human beings, and it is evidence of evolution in language, though it is absent in animal communication. For example, if a cat comes near an individual and they call the cat, it will meow when they ask where it has been the whole day, it will repeat the same sound. It has no ability to communicate about spatial and distant events. This shows that it does not have displacement. Human beings can speak of the past, present, and even the future.

Displacement allows human beings to talk about distant objects and places even when they are not sure of their existence. This feature is essential since it distinguishes humans from other primates. The uniqueness of the environment that human beings live in enables selecting the language to coexist and understand one another. Language evolved even as other human features were underdoing evolution. This gave human beings higher functions such as the distinct language.

Work Cited

Boe, Louis-Jean, et al. Origins of Human language: Continuities and Discontinuities with nonhuman Primates. Peter Lang International Academic Publishers, 2017. Web.

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