The origin of man - World History

The origin of man ( 12,000 million years ) From the Big Bang to the appearance of man.

The oldest event that can be dated in the universe that we know of dates back about 12 billion years. In this first moment, all the energy (and all the space) of the universe was concentrated in one point, which was the origin of a great explosion (big bang). For the first few seconds, the temperature was over a trillion degrees and all the energy was in the form of radiation. During the first 10 seconds the elementary particles were formed and after 15 minutes nuclei of hydrogen and helium were formed,in a ratio of four to one. About 10,000 years later the temperature had dropped to about 100,000 degrees and the first hydrogen atoms were formed. After about 400,000 years the hydrogen began to condense into clouds (future stars), which in turn were grouped into larger clusters (future galaxies).

11,000 million years ago the temperature of the universe was about 3,000 degrees, and the first stars formed: gravity caused the nuclei of many hydrogen clouds to reach high temperatures, on the order of 15 million degrees, which allowed fusion of hydrogen into helium, a process that causes the luminous emission of stars. When stars run out of hydrogen in their core, they are able to continue generating energy by fusing helium into heavier materials. In this way, in the nuclei of the first stars all the chemical elements were formed.that currently exists on Earth. In the largest stars, this process generates more and more energy, until a time comes when gravity is unable to contain it and the star explodes, throwing much of its matter into space. This happens at a different age depending on the mass of each star. Star explosions filled space with new clouds of gas (this time relatively rich in the full range of chemical elements), from which new stars, so-called second-generation stars, formed, among which is the Sun.

The Sun began to shine about 5 billion years ago. At this time the universe had already cooled to about 100 degrees below zero. There are many theories about how the planets of the solar system were formed, but whatever it was, the age of the Earth is estimated at about 4,600 million years. At first it was an incandescent mass whose surface took a relatively short time to cool down. Part of the atmosphere liquefied and thus the seas and oceans were created. The chemical composition of the atmosphere and the oceans was very different from today: the ozone layer that currently protects us from ultraviolet rays did not exist, the atmosphere supported intense electrical activity. These conditions fostered the formation in the waters of increasingly complex and varied chemical compounds: organic compounds that would culminate in the appearance of life forms.

Life on earth arose about 3.5 billion years ago. Thus began an evolutionary process of animals and plants of which we have little data, since the first forms of life were microscopic and then soft animals and plants (algae, worms) that do not leave fossil remains. This first period of life is known as the Precambrian, and extends to the time when we can more closely follow biological evolution through fossils. From here, biologists divide time into eras:

The primary or paleozoic era begins 570 million years ago. Several periods are distinguished in turn:

In the Cambrian period trilobites, molluscs and crustaceans abound . In the Ordovician period (which began 505 million years ago) trilobites continued to abound, echinoderms and brachiopods spread, and the first fish appeared. The Silurian period begins 440 million years ago. Giant armored fish appear , the first land and swamp plants, large sea scorpions.The Devonian period began 410 million years ago. Modern fish and amphibians appear, land plants evolve . In the Carboniferous period (beginning 360 million years ago) amphibians spread, the first reptiles appeared, the earth filled with mosses and ferns, the remains of which formed coal basins. In the Permian period (which began 285 million years ago)reptiles spread, while amphibians lose importance, trilobites become extinct and the first conifers appear.

The secondary or Mesozoic era began 245 million years ago. Its first period is the Triassic, in which the first dinosaurs and large marine reptiles appear. The first mammals also appear. Ammonites abound , new plant species appear, large coniferous forests are formed. During the Jurassic period (beginning 210 million years ago) dinosaurs dominated the Earth. Flying reptiles and the first birds appear , along with new species of small mammals. During the Cretaceous period the first flowering plants appear. At the end of the period, the dinosaurs and many other reptiles became extinct, as did the ammonites.

The Tertiary or Cenozoic era begins 65 million years ago. It begins with the Paleocene, in which mammals proliferate. In the Eocene (60 million years ago) new species of animals (horses and primitive elephants) as well as plants appeared. The Oligocene begins 35 million years ago. Flowering plants proliferate, many of today's mammals appear, including the first primates . Make25 million years ago, in the Miocene, primates multiplied, especially abundant in Africa.

The primates lived comfortably in the trees, fed on fruit, with virtually no predators. However, around 14 million years ago things began to change. Many primates were forced to leave their arboreal habitat. Perhaps their easy life led to overpopulation and some groups were forced out of the forests into the savannahs, a hostile environment for animals unable to digest grass and poorly gifted for hunting. From this time date the oldest known remains of a species of primate called Ramapithecus,that populated a good part of Europe, Africa and Asia (the first specimen was found in India). Traces of an upright position can be seen in its skeleton. We can assume that these displaced primates compensated for their weakness by forming packs, in the style of hunting mammals. The upright posture allowed each member of the pack to maintain visual contact with the rest, so that they could warn each other more efficiently if they detected any danger. Thus, natural selection favored the individuals best gifted for the "uncomfortable" upright posture.

Ramapithecus went extinct 8 million years ago, but it was not the only primate expelled from paradise. There were other species in the same circumstances that survived more or less time. In general, these hunting monkeys are called hominids. From about 6 million years ago , various species of hominids grouped by biologists under the genus Australopithecus appeared in East Africa . In reality, they are the first to which the term hominid can be applied without discussion: gradually, the different species of Australopithecusthey were acquiring the upright posture as a habitual posture and their cranial capacity -even though it was small in comparison with that of the current man- was increasing. What was happening was that the hominids compensated for their low survival skills with increased skills: the upright posture meant that they no longer needed their hands to walk, and they soon learned to use them to kill small prey with stones, increased their agility, their ability to communicate and their ability to observe, and all this physiologically corresponds to an increase in the neuronal complexity of their cerebral cortex.

The Pliocene began about 5 million years ago , with a cooling of the climate that caused the extinction of many large mammals. However, Australopithecus they proliferated and were forced to spread, since there were not many prey within their reach and a small portion of territory could not feed many individuals. Little by little they were occupying all of East Africa, from Ethiopia to the extreme south. Nature then provided one more aid to hominids: delayed maturation. At one point, hominids appeared with a genetic defect: they were born prematurely and their growth was too slow. At first glance, this was a serious drawback: over time, the pups came to be born without hair, without teeth, with a braincase still unwelded, unable to walk, and took an inordinate amount of time to fend for themselves. However, these drawbacks were more than offset by a single advantage: a longer childhood meant more time to learn. Indeed, the young of living primates show a high degree of curiosity during their relatively brief juvenile period, but then it disappears almost completely. Hominids retained their interest in observing and learning throughout their lives, and this made them noticeably more intelligent. This is the reason why natural selection stimulated retarded maturation, which became more acute throughout the successive species of hominids. A few ago the young of living primates show a high degree of curiosity during their relatively brief juvenile period, but then it disappears almost completely. Hominids retained their interest in observing and learning throughout their lives, and this made them noticeably more intelligent. This is the reason why natural selection stimulated retarded maturation, which became more acute throughout the successive species of hominids. A few ago the young of living primates show a high degree of curiosity during their relatively brief juvenile period, but then it disappears almost completely. Hominids retained their interest in observing and learning throughout their lives, and this made them noticeably more intelligent. This is the reason why natural selection stimulated retarded maturation, which became more acute throughout the successive species of hominids. A few ago and this made them noticeably smarter. This is the reason why natural selection stimulated retarded maturation, which became more acute throughout the successive species of hominids. A few ago and this made them noticeably smarter. This is the reason why natural selection stimulated retarded maturation, which became more acute throughout the successive species of hominids. A few ago2.5 million years ago a new species appeared among Australopithecus that can no longer be included in this genus. It was Homo habilis, to which, as we can see, biologists have assigned the new genus called Homo.

Homo habilis surpassed Australopithecus in cranial capacity and intelligence. As proof of this, we find that Homo habilis was the first hominid that learned to carve stones to make them sharp or sharp. He thus had significantly more efficient hunting weapons. With the appearance of the genus Homo and its ability to manufacture stone tools, the so-called Stone Age begins, whose first period is known as Paleolithic and whose first stage, in turn, is the Lower Paleolithic. TheHomo habilis spread rapidly through the territories inhabited by Australopithecus. Shortly after its appearance there was a drastic climate change: temperatures dropped significantly across the planet. Since the Precambrian, the Earth had gone through several periods of cold known as ice ages, some of which had made some species extinct, but this was the first ice age faced by hominids.

Obviously, living conditions worsened. Hunting was scarcer and winters were periods of famine. Despite this, the hominids adapted to the circumstances. Furthermore, in the middle of the ice age, 2 million years ago, a new species of the genus Homo arose: Homo erectus. With him begins the quaternary era, whose first period is known as the Pleistocene. The glaciation lasted about a million years, that is, until 1.5 million years ago, but the Quaternary era reserved four more glaciations, separated by brief interglacial periods.

The first glaciation of the Quaternary era began a little over 1 million years ago and was more intense than the previous one. The competition between the different species of hominids ended with the extinction of Australopithecus shortly after the start of the ice age and that of Homo habilis 800,000 years ago . Homo erectus survived , among other things because it learned to use fire.At that time, he did not know how to produce or control it, but rather found it when lightning set a tree on fire. Maybe he learned to keep it as something valuable. The ice age ended about 700,000 years ago and it couldn't have been long before Homo erectus learned to control fire. This meant greater protection against the cold and carnivorous animals, as well as the possibility of feeding on the meat of many animals that it was difficult to digest raw.

The second glaciation of the Quaternary era lasted from 600,000 years ago to just over 300,000 years ago. During this time, Homo erectus learned to organize itself to hunt large mammals. Their way of life was already very similar to that of other hunting mammals, since their intelligence had already more than compensated for their physical inferiority.

Thus, climatic adversity was no longer a serious obstacle for Homo erectus, which began to proliferate, but, like Australopithecus, found that each small group required a large amount of territory to meet their needs. , so it gradually spread throughout the Earth. However, the total number of inhabitants should never have exceeded half a million. After a brief interglacial period , the third glaciation occurred, from just over 200,000 years ago to just over 100,000 years ago.At its end, Homo erectus already occupied half the planet: it populated all of Africa, a good part of Asia and almost all of Europe (except the north). He had also learned to make cabins that would protect him from the elements in the absence of natural caves, which until then had been his only refuge.

During the third ice age, the first forms of two new species arose: Homo sapiens and Homo neanderthalensis. A pre-Neanderthalian fossil of at least 200,000 years was found in Germany and a fossil from about 100,000 years ago, the ancestor of Homo sapiens, has been found in Israel, along with Neanderthal remains and the last vestiges of Homo erectus, which became extinct about 90,000 years ago. years. With the appearance of these species begins the Middle Paleolithic.

The cranial capacity of the new species tripled that of Homo habilis. At first, the differences between Homo neanderthalensis and Homo sapiens were small, as were the cultural differences with respect to Homo erectus. However, at the beginning of the fourth ice age, around 80,000 years ago, we already found a clearly defined Neanderthal culture. Among their new customs was that of burying the deceased, and among their new skills the manufacture of arrows.Regarding the burials, it is not reasonable to assume in them a capacity for abstract or religious thought, but we can glimpse a certain degree of self-awareness. Natural selection fostered the existence of affective relationships between parents and children to a greater degree than is usual in other animals, since absolutely invalid offspring could not survive without a good dose of patience from their parents. Their young were probably the first to laugh as a resource to please and keep their parents' attention. These affective relationships must have been maintained between adults,

Homo sapiens and Homo neanderthalensis spread across Europe, Asia, and Africa. They hunted all kinds of animals and efficiently adapted to each environment. About 40,000 years ago Homo sapiens became the first human settler in Australia . Some 35,000 years ago it began to manifest its cultural superiority over Neanderthal man, thus beginning the Upper Paleolithic. A good proof of this superiority is that the world population went from just over a million inhabitants in a very short time to almostfive million. The oldest known remains of prefigurative art (incisions and decorative marks in bone and stone) correspond to this period. The earliest known samples of figurative art (animal heads and forequarters painted in stone) date to around 30,000 years ago.This advance must be associated with a significant intellectual evolution. It is impossible to put dates on this, but man acquired the capacity for abstract thought, that is, the ability to think about something without the need for any external stimulus that prompted him to do so. It also developed articulated language: hominids had been communicating with each other with great efficiency for a long time, but always through signs whose meaning was fixed by the context (a scream at a given moment could be the signal to start a joint attack on a prey, or the indication of some danger whose nature had to be perceived directly, etc.). Articulated language meant the possibility of referring to something unequivocally regardless of the context. Perhaps the schematic figures were at first a method of agreeing on the meaning of the words, of agreeing on what game they were going to look for, perhaps it remained the custom to draw pictures of the prey they hoped to hunt, perhaps they came to imagine that drawing the animals was a magical way to attract them. It is difficult to know how these first men conceived of the world. perhaps they came to imagine that drawing the animals was a magical way to attract them. It is difficult to know how these first men conceived of the world. perhaps they came to imagine that drawing the animals was a magical way to attract them. It is difficult to know how these first men conceived of the world.

As Homo sapiens As he became aware of his existence in the world, he must have perceived his weakness and impotence in the face of nature: there were ferocious animals that it was better not to face unless extremely necessary, others, on the other hand, could be mastered with skill. On the other hand, there was nothing to do against the forces of heaven, lightning and thunder. No doubt the Sun and the Moon must have intrigued him. He probably came to the conclusion that very powerful and fickle-tempered beings inhabited heaven, and it was better to keep them happy, since they exerted great influence on earth. Whether or not there was good hunting was in the hands of these beings, whether or not women had children... The imagination of theHomo sapiens faced with the unknown could go a thousand different paths, creating beliefs of all kinds, accompanied by rites and customs. It is difficult to know what specific purpose the objects that today we describe as "artistic manifestations" would have. Female figurines made from about 27,000 years ago are known . From here pictorial images, bas-reliefs and increasingly perfected sculptures are produced.

Some 25,000 years ago , Neanderthal man became extinct, making Homo sapiens the only human species on Earth and we can now refer to him simply as "man". Other than minor racial differentiations, no major physiological evolution has taken place since then. The extraordinary evolution of man has been purely cultural. At least 23,000 years agoman populated America for the first time. He accessed it from Siberia, crossing a dry Bering Strait (the sea level was lower than today due to ice age) or frozen. Thus, man did not take long to populate practically the entire Earth.

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