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 stratigraphic samples where the stone tools are located. As long as you know the age of the soil layer, you will also know the age of the stone tools of Komiks found in the soil layer. However, many commonly used dating methods, such as radioisotope dating, photoluminescence dating, etc., either cannot measure soil samples tens of thousands of years ago, or are not suitable for dust deposits such as yellow soil.
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 in the positive polarity period, the compass points to the north pole of the earth, and when the reverse polarity period comes, the pointing point to the south pole of the earth.
This Cinema‘s 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 polarity of the magnetic substance recorded by magnetic substances, and then compare the 2.58 million years ago.The specific time when the geomagnetic reversal time occurs in geology, as well as the historical time of each polar era, can be used to calculate the age of magnetic matter. Wu Yi explained that during a long geological period, after the later soil layer was superimposed on the original soil layer, the later magnetism would be superimposed on the original soil layer. However, because the original magnetism was the strongest and stable, after the heating treatment, the later superimposed magnetism could be eliminated and only retained. 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 sample and make it into small soil blocks of 2 square centimeters; then each small soil block is heated with a thermal demagnetizer, and the temperature is from 0°C to 680°C; then use the “SuperBabaylan to measure it, and the original magnetic direction obtained by the soil layer at that time can be obtained, which can determine its age.
Scientists found that the bottom 28th layer of loess (L28) showed a short positive polarity, and this layer of Komiks 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 wasThe late “Odewey Incident” (dating from 1.78 million to 1.95 million years ago). Since the Oduwee incident lasted for 100,000 years, it was denied because it did not meet the L28 layer of soil. 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 when the Reunion incident occurred.
According to reports, the researchers conducted paleogemagnetic dating on more than 700 sets of loess samples in the Shangchen Village section.
Changing the 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’ origin of Africa, because the stone age of the site was far earlier than the time when humans walked out of Africa, which means that humans had left Africa at least 1.8 million years ago. In this regard, Zhu Zhaoyu said that the discovery in Shangchen Village before was 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 3 million years ago, but also a series of discoveries from ancient apes, erectiles, Homo erectus, and Homo erectus to Homo sapiens sites, which can form a continuous sequence of changes in the history of human development. Other regions outside Africa do not have such continuous Komiks. However, this discovery greatly updates the history of human activities outside Africa, and this will prompt new considerations to be made on the pattern of early human origin, migration, spread and evolution.
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