Age measurement for Sanxingdui
China News Weekly reporter / Ni Wei
Published in the 1050th issue of "China News Weekly" magazine in 2022.7.4
Since the systematic archaeological excavation started again in Sanxingdui in 2020, phased results have been announced several times, and newly discovered cultural relics such as gold masks and bronze masks have been gradually released.
On June 13 this year, the Sichuan Provincial Institute of Cultural Relics and Archaeology once again released new results in Guanghan, announcing that nearly 13,000 cultural relics have been excavated in six artifact pits.
Another less dramatic new achievement is actually groundbreaking.
The Sichuan Institute of Archaeology announced that after dating nearly 200 samples, it was found that the dating data were concentrated between 1131 BC and 1012 BC, which is equivalent to the late Shang Dynasty in the Central Plains, about 3200 to 3000 years ago.
The result, the court said, resolved disputes over the past 30 years over the burial age of the "sacrificial pit".
In a series of mysteries about Sanxingdui, Shi is one of the core areas.
In the eyes of archaeologists, age and nature have always been the keys to answering the ultimate question of Sanxingdui culture.
Due to the lack of technical means during the excavations in the 1980s, the question of age has not been answered with certainty.
As Zhu Naicheng, a researcher at the Institute of Archaeology, Chinese Academy of Social Sciences, said in an article, "For a long time, the academic community has questioned the age of the Sanxingdui civilization, that is, when did the Sanxingdui civilization form, when did it end, and how long did the entire Sanxingdui civilization last? It has not been explored in depth.”
The resumption of excavations in 2020 are six utensil pits with a large number of cultural relics buried. The utensil pits are the most concerned part of the Sanxingdui site, but not all.
However, the determination of the burial age of the utensil pit is an important step in the study of the entire Sanxingdui site and even the Sanxingdui culture.
How to Date Sanxingdui
A key contribution to the dating of the Sanxingdui artifacts pit is the carbon 14 technology.
The institution responsible for this inspection is the "Joint Laboratory of Archaeology and Chronology" jointly established by the Archaeological Research Center of the State Administration of Cultural Heritage and the School of Archaeology and Museology of Peking University.
The joint laboratory is located in an old house with gray tiles and white walls at Peking University. It was just established in March this year. In fact, the carbon 14 dating of Peking University has a history of nearly 50 years.
There are two most well-known carbon 14 dating laboratories in the field of Chinese archaeology, and the other belongs to the Institute of Archaeology of the Academy of Social Sciences.
If a national archaeological project needs carbon dating testing, it must be sent to one of these two institutions.
According to previous reports, Peking University tests two or three thousand carbon-14 samples every year.
Sanxingdui successively sent more than 200 carbon 14 samples.
Wu Xiaohong, a professor at the School of Archaeology and Museology at Peking University and director of the Joint Laboratory of Archaeology and Chronology, wrote in an article that this dating strives to produce at least 6 reliable carbon 14 dating data for each of the 6 pits.
First, 10 samples were selected in each pit and sent to the laboratory for pre-treatment: the plant debris should be treated with acid and alkali to eliminate carbon pollution in the environment; in addition to the acid and alkali treatment of bone residue samples, Collagen is also extracted and further hydrolyzed, centrifuged, and freeze-dried to prepare gelatin.
During this process, many samples were eliminated one after another due to poor preservation conditions.
In this way, new samples need to be added, so the total number of samples reaches more than 200 copies.
The samples from Pit 5 and Pit 7 were not well preserved, and less than 6 samples finally produced reliable data.
Maybe it was a sacrificial ceremony, maybe it was a burial of waste products, maybe it was a fire, and the Sanxingdui utensils buried pits were generally burned.
Wu Xiaohong said that there are three main forms of plants after burning. Among them, the most suitable state for dating is: the plants are dehydrated at high temperature during the burning, but because they are not exposed to oxygen, the plants form carbonized lumps and are not fully burned into ashes.
Most of these tangible plant debris are relatively compact and dense in texture, which well preserves the original carbon-containing components of plants. After post-processing, the pollution brought by the burial environment can be effectively eliminated, which is conducive to accurate dating.
Animal bones are often good samples for carbon 14 dating because the collagen in bones is largely free from environmental carbon pollution.
However, basically no formed bones can be seen in the Sanxingdui utensil pit. They are all bone slag, and most of the collagen has been degraded. It is probably due to insufficient combustion, hot humid climate and acid soil erosion.
Wu Xiaohong said that the 38 carbon 14 data of the four burial pits obtained so far are all from plant carbon scraps, and no collagen can be successfully extracted from the bone residue samples.
Carbon fourteen is a radioactive isotope of carbon, first discovered in 1940.
Since the half-life of carbon fourteen is more than 5,000 years, and it is widely present in organic objects, the age of carbon fourteen can be inferred based on the residual carbon fourteen composition of the organism, as long as its living age does not exceed 50,000 years.
In 1949, Willard Libby, a professor of chemistry at the University of Chicago, invented the carbon dating method and won the Nobel Prize in Chemistry 11 years later.
In 1965, atomic energy experts Qiu Shihua and Cai Lianzhen, who were transferred from the Institute of Physics, Chinese Academy of Sciences to the Institute of Archaeology, Academy of Social Sciences, established China's first carbon 14 laboratory through independent research and development of equipment.
The laboratory at Peking University was established in 1973.
Carbon-14 detection technology, like a chronological ruler extending into ancient times, has naturally gained the most widespread application in archaeology and geology.
Before carbon 14 technical dating, through stratigraphy and typology, experts could determine a vague age range for the site, but it could only be qualitative, and it was impossible to obtain quantitative data for specific years.
For example, scholars can judge that this ancient tomb is of the Peiligang culture of the Neolithic Age, and that the city site is of the Yangshao culture, but they do not know whether it is 5,000, 6,000, or 7,000 years from us.
Qiu Shihua once said that before the application of carbon 14 dating, "prehistoric chronology was almost entirely based on subjective speculation or inference".
In the 1990s, on the basis of more than 2,000 carbon-14 dating data, the Chinese prehistoric archaeological chronology framework since the Late Paleolithic was established.
In 1986, Sanxingdui No. 1 and No. 2 pits were discovered under a brick factory, and the unearthed artifacts made it "stunned the world".
No samples were specially extracted for dating during the excavation. The dating of pits 1 and 2 was done in 1997.
But only a few samples were tested sporadically.
At that time, the results were not finalized.
The debate on the age of Sanxingdui has never stopped, and various theories have emerged one after another. Most of them tend to advance the age of Sanxingdui to the early Shang Dynasty—that is to say, before the earliest age of bronze civilization in China, it seems to have emerged out of thin air. of.
This unfounded conjecture conforms to and fuels the trend of turning Sanxingdui into a "myth".
"Based on this, various imaginative sayings have emerged. For example, the Sanxingdui bronze civilization is a 'visitor from outside the sky'." Wu Xiaohong said.
In fact, these speculations all come from the people, and no such inferences have appeared in the academic world.
The main reason is that there is no widely convincing dating data.
At that time, the conventional carbon-14 dating method was used, which required a large amount of samples.
After the animals and plants in the two utensil pits are burned, the organic components are poorly preserved, and it is difficult to extract a sufficient amount of pure organic components.
As a result, the two sets of data finally obtained have a large error, and the age range of the 95.4% confidence level is as large as 500 to 600 years. In the eyes of archaeologists, it is not enough for detailed discussion.
The lack of reliable absolute age data for pits 1 and 2 leaves room for widespread controversy.
The opportunity came after more than 30 years.
In 2019, archaeologists at the Sanxingdui Workstation recovered the edge of the earth and stone construction platform of the No. 1 and No. 2 pits and found a corner similar to the buried pit.
Immediately, six sacrificial pits reappeared, and field excavations began the following year.
This time, archaeologists systematically collected carbon-14 dating samples.
Moreover, the six pits are sandwiched between the first and second pits, and the eight pits seem to be closely related, and it may be possible to find out their ages at the same time.
Today, the domestic carbon 14 dating technology is very different from that in the past.
Wu Xiaohong told China News Weekly that Peking University has been equipped with accelerator mass spectrometry instruments, making it possible to measure tiny carbon 14 samples, which can measure 1mg of carbon samples, which is thousands of carbon less than the conventional carbon 14 dating method. times.
For the carbonized plant debris in Sanxingdui, accelerator mass spectrometry technology came in handy.
The results show that there is a 95.4% probability that the formation ages of pits 3, 4, 6 and 8 for which sufficient carbon 14 dating data have been obtained falls between 1200 BC and 1010 BC.
On this conclusion, Wu Xiaohong concluded in the article: "There is no suspense when the Sanxingdui burial pit was buried in the late Shang Dynasty. If you ask whether it can be said that it has entered the beginning of the Zhou Dynasty, from the perspective of the distribution of chronological data, it is possible. Yes, but the probability of that is very low."
What mysteries can dating solve
Although the age has been determined, the controversy has not yet subsided.
There are too many questions about Sanxingdui, and the problems that can be clarified by this excavation and research are very limited.
To borrow the words of archaeologist Xu Hong, archaeological work is always "unknown is always much more than known".
For example, these pits, which are called "blind boxes", have not yet reached a consensus on their basic nature.
Regarding the nature of the eight pits, there are currently two main views, one is the "buried pit" caused by accidental events, and the other is the "sacrificial pit" that was planned to be built many times.
"Buried pits" means that these pits were formed at one time. Archaeologists who support this view speculate that the ancient country of Sanxingdui suffered a major or even catastrophic change, so that a large number of destroyed and exquisite artifacts were dug and buried.
What exactly happened?
There are "war theory", "coup theory", "temple fire theory" and so on.
If it is a "sacrificial pit", it means that the buried objects are more routine and ritual, and are gradually buried over a long period of time.
Those who hold this view, including some experts from the Sichuan Provincial Institute of Cultural Relics and Archaeology, the host unit of the excavation, published an official archaeological report in 1999 named "Sanxingdui Sacrificial Pit".
When Ran Honglin, director of Sanxingdui Archaeology Institute of Sichuan Provincial Academy of Archaeology mentioned "sacrificial pit" in his paper, he also had to explain: "This article uses the name of 'sacrificial pit' used in the past, but it does not mean that we agree with what 'sacrificial pit' represents. The nature of K1 and K2 are sacrificial pits, on the contrary, we believe that they are not sacrificial pits." This means that there are also different opinions within the Sichuan Provincial Institute of Archaeology.
The two different views on the utensil pit may lead to different conclusions when understanding some unsolved mysteries of Sanxingdui.
Sun Hua, a professor at the School of Archaeology and Museology at Peking University who has been studying Sanxingdui for a long time, believes that the Sanxingdui Artifact Pit is a "buried pit".
He explained to the media that the dating results fell between about 1100 BC and 1050 BC, which was the time when the Shang Dynasty declined and the Zhou Dynasty rose. According to this background, the temple in Sanxingdui was burned and buried. The formation may be related to the disputes within the Sanxingdui Kingdom at that time.
Perhaps in terms of choosing goodwill objects, some nobles agreed to rely on businessmen, and some nobles advocated supporting Zhou people. Different political opinions and other factors led to the turmoil in Sanxingdui.
Experts who agree with the "sacrificial pit" point of view believe that the national nature of Sanxingdui as a sacrificial center has led to excessive concentration of human and material resources and consumption of social wealth. Ability, about the late Shang Dynasty, the ancient Sanxingdui theocracy gradually lost control, and eventually a serious survival disaster and social panic occurred.
So, can the results of this carbon 14 dating resolve the debate over the nature of the artifact pit?
Wu Xiaohong, the person in charge of the dating work, pointed out that the formation time of the several buried pits found in Sanxingdui is roughly the same.
At present, there is no way to obtain more detailed age data, and in this case, it is not helpful to further compare the early and late relationship between each buried pit from the perspective of carbon 14 dating data.
Through this dating, it is not yet possible to determine whether these artifacts were buried at one time or in batches in an orderly manner, so as to solve the problem of the nature of the artifact pits.
Moreover, this dating conclusion is generally close to the previous judgment based on stratigraphy and typology.
The archaeological report "Sanxingdui Sacrificial Pit" in 1999 concluded that the artifacts of No. 1 Sacrificial Pit should be buried at the end of the first and second phases of Yin Ruins; between four periods.
Yin Ruins was the capital of the late Shang Dynasty, which means that the age of the Sanxingdui utensil pits coincided with the late Shang Dynasty, and it has long been known.
Prior to this, experts deduced that Sanxingdui was inextricably linked with the Xia and Shang eras in the Central Plains through the correlation between Sanxingdui artifacts and Central Plains artifacts.
There are some typical artifact clues, such as the bronze statue on the top of the head, the yazhang in the hand, and the image of a large number of dragons, showing the profound penetration of the Central Plains culture into the southwest.
The bronze statues, copper pots and copper pots unearthed in Sanxingdui are typical bronze wares of Yin and Shang culture in the Central Plains. The discovery of a large number of gold objects is consistent with the ancient tradition of using gold objects in the half-moon zone.
"It can be said that the ancient Shu people and the Central Plains have a considerable degree of agreement in core values or cognitive systems," Lei Yu, head of the Sanxingdui Site Workstation of the Sichuan Provincial Institute of Cultural Relics and Archaeology, said in an interview with the media, "although not by (the Central Plains) ) directly, but should have long been a big family in terms of cultural identity.”
To explore the age of Sanxingdui culture, it is not enough to just study the eight pits found in the sacrificial area. These pits can only represent the later period of Sanxingdui civilization.
The early cultural relics of Sanxingdui include the Rensheng Village cemetery on the west side of the Sanxingdui site, the second-phase city wall of Sanxingdui Dacheng, as well as the remains of the jade pits in the Yanjia courtyard in Yueliangwan, the remains of Gaopian pits, and the remains of warehouses and bags in Yueliangwan, etc. .
Zhu Naicheng, a researcher at the Institute of Archaeology of the Chinese Academy of Social Sciences, inferred that the Sanxingdui civilization began to form between 1600 BC and 1500 BC, and ended around 1050 BC, and existed for about 500 years.
"I think the issue of Sanxingdui needs to be taken slowly, and the entire excavation and research work is just the beginning." An expert who has been deeply involved in the archaeological work of Sanxingdui said that there are many differences in terms of the age of Sanxingdui, whereabouts of Sanxingdui, and important buildings. Da, "There are still many phenomena that are very important. We need to study them bit by bit, and don't rush to make a conclusion."
"China News Weekly" Issue 24, 2022
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