Professor Ian Morris provides a quantitative measure for documenting the long-term historical trajectory of human civilization, which he calls the Social Development Index, that is, the ability of a society to get things done. Society is made up of people, and people who are also animals need to consume energy. According to the principle of conservation of energy, for a society to be able to do things, it needs the ability to ingest and use energy. So to measure the degree of social development, the most important index is the ability to absorb energy and use energy. The following is an explanation of this measurement method from three aspects: measurement content, measurement method, and measurement object. Morris divides a society's ability to absorb and use energy into four areas: the ability to absorb energy, the ability to organize socially, the ability to information technology, and the ability to mobilize for war. The ability to consume energy mainly refers to the ability of each member of society to consume food, fuel and raw materials on a daily basis. Social organization capacity is defined as the number of people in the largest permanent residence unit in a society, and the population of the largest city for a considerable period of time. The larger the population, the higher the need for the capacity of social organizations. Members of social organizations need to communicate, store, and memorize all kinds of information every day, so information technology is also an important way for humans to use energy. War as an important source of human energy consumption need not be repeated. These four aspects are not the whole of human activity, but they are the most representative ways in which human beings consume and use energy. More crucially, these four criteria can be compared horizontally in all societies, and can also be compared vertically over a long time frame. Because the entire evolutionary history of mankind is actually the history of ingesting and using energy, and organizing society, forming population centers, exchanging information, and waging wars are also the most important activities that all human societies will carry out.
To understand human characteristics, it is necessary to understand the environment in which human beings live. The Earth is 4.5 billion years old, living things are only about 1.5 billion years old, and humans are only 150,000 years old. The natural environment is crucial to the impact of all living things, of which climate is the biggest influence. Earth's climate began to undergo a major change about 50 million years ago, when the movement of the continental shelf moved most of the land to the northern hemisphere, while the southern hemisphere was largely dominated by oceans. Another change was 14 million years ago, when volcanic action to form the continental shelf basically stopped, and the Earth's temperature also dropped, so the Antarctic formed a year-round snow, while the Arctic did not melt until 2.75 million years ago, so it did not form a year-round snow accumulation until 2.75 million years ago. Against this backdrop, the Milankovic cycle began to have a cyclical impact on today's Earth's climate. The Earth's orbit around the Sun is not perfectly circular , because it is often elliptical due to the gravitational pull of other planets. In addition, the rotation process of the Earth usually has an incline, and the axis of rotation also has an precession. Affected by these three factors, the Earth's climate forms a three-year cycle with cycles of every 26,000 years, 41,000 years, and 96,000 years. These three cycles have caused the Earth to receive different amounts of sunlight and heat, forming glacial and interglacial periods of the climate.
The Glaciation Period has occurred 40 to 50 times in history, with the two most serious occurring 190,000 years ago and 90,000 years ago, a period that played a key decisive role in the origin and early development of mankind. At the height of the Ice Age, glaciers in the Arctic Ocean alone covered northern Europe, Asia, and the Americas. Most of the water on the Earth's surface was absorbed into glaciers, and the Earth became very dry, with the sea level 300 feet below what it is now. Coupled with glaciers reflecting sunlight back into the atmosphere, the temperature is lower, plants and animals are reduced, the carbon dioxide that produces a greenhouse effect in the air is reduced, and the temperature is further reduced. Homo sapiens, the ancestor of modern humans, appeared around 150,000 years ago, when harsh climatic conditions allowed them to live in a very limited area of Africa near the equator. The vast majority of geneticists and archaeologists believe that the total number of humans at that time fell to about 20,000 at one point, and humans did not show any signs of conquering the earth in the future. This is the darkest time in human history. But around 70,000 years ago, human luck began to improve, when the Milankovic cycle changed in the opposite direction, and the eastern and southern parts of Africa began to become warmer and wetter, providing humans with better natural conditions for hunting and gathering, and the population began to grow rapidly with the increase of food. It was also at this time that man, as a unique animal, began to show his true superiority.
When humans first appeared, they were very different from other animals, even their "close relatives" the apes. This distinction was not fully demonstrated before the climate warmed, but once the climate created favorable conditions, humans began to show great advantages. Compared with other animals, the biggest feature of humans is that the brain capacity is huge and the computing power is super. Although the brain is only 2% of a person's body weight, it consumes 20% of a person's energy. If humans are born after the brain is fully mature, the mother will not be able to give birth at all. To solve this problem, humans can only give birth to fetal brains before they are fully developed. This is different from other mammals. Whether cattle, horses, sheep, lions, tigers, these animals can soon stand, grow, live, and even prey on their own after birth. However, when people are born, they are still far from maturity and independent life, and it will take several years to stand, walk, and speak, and the brain can fully mature. Therefore, the mortality rate of human newborns is very high, but the advantages after maturity are also obvious. When the climate becomes favorable to living things, human superiority is particularly prominent. This advantage is fully reflected in the first leap of human civilization, that is, the leap out of Africa.
