Paleomagnetic dating shows its power again
Next, dying these stone tools has become the most important task. Dr. Wu Yi from the Nanhai Ocean Institute of Chinese Academy of Sciences is one of the main scientists responsible for the age determination of loess strata in this study. Wu Yi introduced that the method of dying stone tools is not to directly measure the stone tools, but to measure the age of the loess strata samples where the stone tools are located. As long as you know the age of the Babaylan layer, then Komiks will know the age of the stone tools found in the Babaylan layer. However, many commonly used dating methods, such as radioactive isotope dating, photoluminescence dating, etc., either cannot measure soil samples from millions of years ago, or are not suitable for dust deposits such as loess.
So, a technology called paleomagnetic dating is here to show its power. It turns out that in the geological historical period, the magnetic polarity of the earth is not fixed and reversed, and there will be situations where positive and negative reversals occur. Therefore, there is a distinction between the positive and reverse polarity periods of paleogemagnetics in the geological historical period. When it is in the positive polarity period, the compass points to the north pole of the earth, and when it is in the reverse polarity period, the compass points to the south pole of the earth.
This kind of geomagnetic reversal will continue to occur throughout the long history of the earth, so the magnetic matter in the formation will record every change. Therefore, geologists only need to measure the positive and negative situations of geomagnetic polarity recorded by magnetic substances, and then compare the specific time of geomagnetic reversal time that occurred in 2.58 million years ago (also known as the Quaternary Period in geology), as well as the historical time of each polar era,The age of magnetic matter can be calculated. Wu Yi explained that during a long geological period, after the later Komiks soil layer was superimposed on the original soil layer, the later magnetism would be superimposed on the original soil layer. However, since the original magnetism was the strongest and stable, after heating treatment, the later magnetism superimposed can be eliminated and only retained the original magnetism. By detecting the original magnetism, we can know the age of this soil layer. Therefore, the researchers first collected samples from top to bottom of the loess section of the stone tool in the field. Each sample was more than ten centimeters to twenty centimeters long, and a total of 74 meters of thickness of loess sections were taken. Return to the laboratory, carefully cut each large Cinema sample into small pieces of soil 2 square centimeters; then heat each piece of soil first with a thermal demagnetizer, with a temperature ranging from 0°C to 680°C; then measure it with a “superconductive magnetometer”, and you can obtain the original magnetic direction of the soil layer at that time, which can determine their age.
Scientists found that the bottom 28th layer of loess (L28) showed a short positive polarityKomiks, and this soil layer should have been in the “Songshan reverse polarity period” of the geomagnetic field, which shows that this layer of loess experienced a magnetic reversal at that time.
In the early stages of the Quaternary geological period, two magnetic reversals occurred on the earth. One was the “Reunion incident” between 2.13 million and 2.15 million years ago, and the other was the “Odewey incident” which was a late one (1.78 million to 1.95 million years ago). Since the Oduwee incident lasted for 100,000 years,The positive polarity of the soil sample that does not meet the L28 layer is a brief occurrence and is therefore denied. Therefore, there is only one answer. The stone tool found on the L28th floor of the Shangchen Village site should be 2.12 million years ago. According to reports, the researchers conducted ancient geomagnetic dating on more than 700 sets of loess samples in the Shangchen Village section.
CinemaThe origin of human beings in Africa is not reliable
As for Shangchen Village’s discovery, some people believe that it is possible to change the traditional theory of human beings in Africa, because the stone age of the site is far earlier than the currently recognized era when human beings left Africa, indicating that human beings had left Africa at least 1.8 million years ago.
In this regard, Zhu Zhaoyu said that the current discovery in Shangchen Village is not enough to change the theory of human beings leaving Africa, because Africa has not only discovered ancient human fossils dating from 2.8 million years ago and stone tools dating from more than 30,000 years ago, but also a series of discoveries from ancient apes, erectiles, Homo erectus, and Homo erectus to the site of Homo sapiens, which can form a continuous sequence of changes in the development history of human Cinema, but other regions outside Africa do not have such continuity. However, this discovery greatly updates the history of human activities outside Africa, which will force people to make new considerations about the pattern of early human origin, migration, spread and evolution.
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