How did humans form?

The Transition from Apes to Humans The origins of various things in the ancient history of the world are extremely difficult to explain, because humans in the origin period had no self-awareness of the origin events themselves.

What is currently popular is the ape hypothesis. From a comparative anatomy perspective, paleoanthropologists have analyzed hundreds of similarities between humans and modern great apes (gibbons, gorillas, orangutans, and chimpanzees), as well as the differences between humans, the great ape family, and other animals. This point shows that humans and modern great apes are related and have the same ancestors. ① Existing materials include Protopithecus, the earliest ancient ape discovered in Egypt, which lived 30 million years ago; Egyptian ape, which lived 26 to 28 million years ago. Later fossils include Sylvania apes, which are between 23 million and 10 million years old. They are widely distributed and have been found in Asia, Europe, and Africa. The above ancient apes are all forest-dwelling animals, walking on all fours and belonging to a group of tree-climbing apes. But it is still a mystery which one of them is the ancestor of human beings or whether such an ancestor fossil has not yet been found by humans. What can currently be inferred is that the transition from apes to humans began around 30 million to 10 million years ago.

There are two transitional fossil representatives from about 10 million years ago to about 3.8 or more than 2 million years ago. One is Ramapithecus and the other is Australopithecus. The ancient apes in the transition period have separated from the ape system and developed in the direction of humans, and their performance is to walk upright.

The typical material of Ramapithecus is a fragment from the right side of the maxilla, which was unearthed at the border of India and Pakistan in 1932. In the 1960s, most paleoanthropologists included it in the human system. In addition to India, since the 1950s, Ramapithecus teeth and jaw fragments have also been unearthed in China, Turkey, Kenya, Hungary, and Greece, and their existence spans from about 14 million years ago to 8 million years ago. Due to the increasing number of such fossils, the paleoanthropological community has now expressed increasing doubts about including Ramapithecus in the family Hominidae. Many people believe that Ramapithecus is the ancestor of orangutans, but there have been deviations in the reconstruction of jaw fragments and tooth analysis in the past. Therefore, Ramapithecus is only relatively reasonable as a fossil representative of the transitional period.

The transitional Hominidae members that can be talked about with confidence are the Australopithecus belonging to 5.5 million years ago. Its fossils have been found in some countries and regions such as South Africa, East Africa, and China. There are basically two types (some scholars believe that there are 3-4 types, and there are also Australopithecus baumannii species and Alfa species): stout type and slender type. , depending on height and weight. The stout type is about 1.5 meters tall and weighs 54-68 kg; the slender type is about 1.2 meters tall and weighs 45-54 kg. Both were able to walk upright and were found in many places at the same time as fully formed human fossils, extending to 1 million years ago before disappearing. At present, paleoanthropologists at home and abroad generally believe that Homo (genus Homo) evolved from a branch of Australopithecus. Most scholars believe that it is Australopithecus gracilis, and a few scholars believe that it is Australopithecus Afa discovered in Ethiopia. , and other Australopithecus are offshoots that became extinct one million years ago.

In the 1970s, molecular biology technology began to intervene in the study of human origins. The basic idea is to calculate the genetic relationship between humans and different apes based on the similarities and differences between cellular protein macromolecules in humans and apes, thereby compiling a molecular clock for the evolution of humans and apes. The results of molecular biology are similar to fossil materials, that is, members of the transitional period Hominidae separated from certain kinds of great apes around 10 million years ago to 4 million years ago, and humans are most closely related to orangutans or chimpanzees. This is also consistent with the fact that the endocrine, sexual behavior, pregnancy and other anatomical characteristics of orangutans and chimpanzees are closer to those of humans.

The traditional explanation for why a certain kind of ancient ape transformed into a hominin is first of all the vicissitudes of the ecological environment. Changes in the earth's crust and climate occurred in the Miocene and Pliocene, causing large areas of forest to recede. As a result, the usual food of ancient apes was reduced, and some ancient apes were forced to go down to the ground and change from vegetarian to omnivorous. Changes in food structure cause changes in chemical substances in the body. On the other hand, in order to fight against the beasts, the ancient apes that went down to the ground had to free their forelimbs to defend themselves, specifically using sticks and stones. The law of biological evolution is to use it or lose it. The ancient apes with preliminary division of labor in their hands and feet survived under ruthless natural selection, which eventually led to morphological changes. Labor becomes an important driver of transformation here. From a logical point of view, this explanation is reasonable, but of course it also requires reliable and specific evidence from paleogeography and human behavior.

Modern genetics is trying to give a more precise answer to this question. According to genetic theory, the reason for the transition from ape to human needs to find a breakthrough in the variation of genetic material. All animal cells contain genes with genetic effects, including deoxyribonucleic acid (DNA), ribonucleic acid (RNA) and other organic substances. Changes in the animal body ultimately result from mutations in these genetic materials. There may be several reasons for the transformation of ancient apes into humans, such as genetic mutation, variation in chromosome number, individuals with unfavorable traits being eliminated by nature, and genetic drift caused by neutral variation. Natural upheavals and the effects of labor promote genetic variation. Therefore, the issue of human origins is extremely complex, and people's understanding will gradually deepen with the advancement of science.

①

Fully formed human being is the stage of human beings who can make tools. The evolutionary process of human beings has now become relatively clear. Chinese paleoanthropologists divide this process into two major stages: ape and homo sapiens, and each stage is further divided into two periods: early and late.

(1) Early ape man

Lived from about 3.8 million to 1.75 million years ago. The typical fossil representative is the fossil man discovered one after another in the Olduvai Gorge of Tanzania in the 1960s, named Homo habilis and dated to 1.75 million years ago. Also found with the remains of Homo habilis were crude hand-made chopping tools. In addition to the fossils of Homo habilis, foreign paleoanthropologists have also discovered ancient human fossils or separately discovered stone tools in other areas of Kenya, Ethiopia and Tanzania in East Africa, dating from about 3.7 million years ago to 1.8 million years ago. No wait. In short, according to current materials, the length of history of people who can make tools is more reliable at 1.75 million years, and less reliable at 3.8 million years.

Early ape-men had obvious ape-like characteristics, especially their heads. For example, the brain volume is small (500-700 ml), the brow bone and muzzle are prominent, and the frontal bone is low. The height is about 1.2-1.4 meters, reflecting the tendency of the human body to gradually increase in height.

(2) Late ape man

The scientific name is Homo erectus, and he lived from about 1.75 million years ago to 300,000 years ago. There are many and solid fossils distributed in Asia, Africa and Europe. Typical representatives include the Javanese in Indonesia, the Heidelbergensis in Germany, the Beijingers and Lantian people in China, and the East Africans in Kenya.

The Javanese was unearthed from 1890 to 1892, including a skull, a complete thigh bone, three teeth and a mandibular fragment. This is the earliest ape-man fossil discovered, dated to 800,000 years ago. In the 1930s, some new early ape-man fossils including skulls were discovered in Java, with dates ranging from 1.5 million to 250,000 years ago.

Homo heidelbergensis was discovered in the southeast of Heidelberg, Germany at the beginning of this century. It has only one mandible and is about 800,000 years old. Late ape-man fossils have also been discovered in other European countries, such as France, Hungary, and the Czech Republic.

Relatively speaking, among the materials of late ape man, Peking Man fossils are the most abundant and complete. So far, more than 40 bone fossils have been discovered, including 6 skulls, dated to about 400,000 to 500,000 years ago. .

A complete ape-man skull was unearthed in Kenya from 1974 to 1975. In addition, Tanzania in East Africa and Algeria and Morocco in North Africa are also the places where late ape-man fossils were discovered.

The late ape-men showed obvious progress in physical form. Javanese brain volume reaches 750 ml. The average brain volume of Beijingers is 1059 milliliters, their height is about 1.5 meters, their upper and lower limb bones are close to those of modern humans, and they can walk upright similar to modern humans. However, in terms of skull structure, late ape man was still relatively primitive. For example, the nose and eyebrow ridge of Beijingers are still prominent, the forehead is low and flat, and there is no chin. This shows that during the evolution of the human body, the development of the thinking organ lagged behind the labor organ. The reason may be that early humans were instinctively more dedicated to survival labor, and the activities of the limbs were more than the conscious activities of the brain.

(3) Early Homo sapiens

Abroad, they are called Neanderthals or ancient humans, dating back about 300,000 to 50,000 years ago. Its fossils are widely found in Europe, Asia, and Africa, and have been found in more than 500 places alone. The typical fossil representative is a pair of skeletons, including a skull, discovered in the Neanderthal Valley in Dusseldorf, Germany in 1856. It was named Homo Neanderthal, or Homo neanderthalensis for short. Later, similar fossils discovered in Europe, Asia, and Africa were generally called this name. The more famous ones are the Saint-Shabair people and the Mouster people in France, the Maba people and the Dingcun people in China, and the Bodo people and Broken people in Africa. People wait.

The ape characteristics of early Homo sapiens have not completely disappeared, but their physical shape is close to modern humans. For example, the average brain volume is about 1350 ml, which is close to or equal to modern humans. Some Nigerians have even larger brains than the average modern human. However, the structure of the brain is still relatively primitive, and the forehead area where the brain's association center and inhibition center are located is not yet developed. The bone joints of the long limbs, which were previously evidence of more curved walking in the lower limbs, have been fully developed. The animal is of medium height and has a strong build. Regional variation characteristics are clearly evident. For example, although Palestinian Neanderthals and European Neanderthals belong to the same era, they are more similar to modern humans in appearance, with unprotruding eyebrow ridges, well-developed mandibles, and high foreheads. They are among the Neanderthals who have evolved the fastest in terms of physique. The head development of European Neandertals is closer to that of apes. And even in a large area, such as Europe, different types of early Homo sapiens are found, such as the Saint-Shabair type, the Shur type, the Tabon type, etc.

(4) Late Homo sapiens

Modern humans, also called new humans by some scholars, appeared within 50,000 years ago. The early (relative to us modern humans) fossil representatives are mainly 5 human skeletons discovered in a cave near the rural village of Croma in Leuis, France in 1868. They were dated to 50,000 years ago. Their shape has become the same as that of modern humans. No difference. Since then, a large number of late Homo sapiens fossils have been discovered in Europe, Asia, Africa, and Oceania.

The early inhabitants of America and Oceania migrated from the Old World, because no fossils of ancient humans before late Homo sapiens have been found on these two continents. From a historical point of view, residents all over the world today are the descendants of "immigrants" at different times. The term "native" is only a relative term.

Judging from fossil materials, it is estimated that 30,000 years ago, humans jumped from Southeast Asia to Australia via the Pacific Islands in canoes, and then entered the Americas overland through the Bering Strait.

A striking biological characteristic of late Homo sapiens is the emergence of different modern human species. The so-called race refers to a group of people with the same genetic physical characteristics that are different from other groups of people. It is divided according to people's skin color, shape, distribution and color of hair and body hair, eyes, nose, body shape and other external genetic characteristics. The more common one is the trichotomy, which divides late Homo sapiens into Equatorian race or Australian Negroid race (black race), Asian American race or Mongolian race (yellow race), Eurasian race or Europa race. species (white species), and several subspecies in between. The term black, yellow and white mentioned here is just following tradition. In fact, within each race, the range of skin color variation is very large. In the case of the Europa race, skin color can range from almost colorless to almost black.

The birthplace and causes of the formation of human race have also not been resolved. It is estimated that due to long-term isolation and different ecological environments, such as temperature, humidity, viruses, hybrid food, etc., the genetic material of the human body mutates to adapt to the needs of natural selection. On a large scale, the three continents of Europe, Asia, and Africa are mostly the native places of each of the three major human races.