Xinhua News Agency, Lanzhou, August 27th. Title: Has the northwest been dry and rainless?
Listen to how prehistoric animals "say"
Xinhua News Agency reporters Hu Weijie, Yang Yating, Ma Sha
Arid and rainless, desolate and magnificent Gobi, desert, this is the impression many people have of my country's northwestern region.
But has it always been like this here?
Back in time tens of millions of years ago, there was once lush vegetation, dense forests, and tropical and subtropical animals such as giant rhinoceros and shoveltooth inhabited and proliferated here.
Why did the Northwest region become what it is today?
How did this change happen in the time latitude of tens of millions of years?
At the Hezheng Ancient Animal Fossil Museum in Hezheng County, Linxia Hui Autonomous Prefecture, Gansu Province, experts found the answer from the fossil remains of prehistoric animals.
Deng Tao, a researcher at the Institute of Vertebrate Paleontology and Paleoanthropology of the Chinese Academy of Sciences, is mainly engaged in the study of mammals, terrestrial strata and environmental evolution in the Late Cenozoic. He often travels between Linxia Prefecture in Gansu Province and Beijing.
Because of the special basin topography in the Linxia area, a large number of complete ancient mammal fossils have been preserved.
Today, the Hezheng Ancient Animal Fossil Museum has more than 30,000 fossil specimens.
These large numbers of fossil specimens are important clues to unlocking the "code" of climate change in Northwest China.
Deng Tao and his research team discovered that the fossils in the geological sediments of different ages in the Linxia Basin pointed to four different faunas that existed in the area. In chronological order, they were the giant rhinoceros fauna and the shoveltooth fauna. Herd, three-toed horse fauna and real horse fauna.
Each animal group corresponds to a different natural environment.
"The survival of the fittest, the dominant animal group in each period can adapt to the environment at that time." Deng Tao said.
As a result, we can "decrypt" how the climate environment has undergone ups and downs in the past tens of millions of years in northwestern China, as represented by the Linxia region, and even the inland regions of Central Asia.
Walking into the Hezheng Ancient Animal Fossil Museum, a huge restored statue of a prehistoric animal on the left attracts people's attention. It has a long neck and can stand up to 5 meters high at the shoulder.
This is the giant rhinoceros. It lived 42 to 21 million years ago. It is a tall mammal that feeds on the leaves on the top of the canopy.
“The giant rhinoceros could not move in the dense forest. It can be speculated that the natural environment in the northwest was dominated by sparse forest at that time.” Deng Tao believes that the climate at that time was relatively warm and humid, even a little hot.
A large number of shovel-tooth skeleton fossils were unearthed in the Hezheng area. The museum has shovel-tooth skulls from three to four months old to more than 40 years old, and even the skeleton of a shovel-tooth elephant has been restored.
According to experts, the shoveltooth is the second large animal group discovered in Linxia after the giant rhinoceros. They lived in the global warm period, and the temperature was at least 4 to 5 degrees Celsius higher than the current average temperature.
The shovel-tooth elephant made a living by shoveling water weeds, indicating that there were lakes, rivers and dense forests in northern China at that time.
With the uplift of the Qinghai-Tibet Plateau and the end of the global warming period, the shoveltooth fauna was quickly replaced by the three-toed horse fauna.
In the museum, the reporter saw a three-toed horse restored skeleton.
Unlike modern horses, it has 3 toes on each leg and is good at running in open areas.
According to reports, the forest degradation and the rise of grasslands in the northwest at that time were particularly suitable for the survival of the three-toed horse population.
"At that time, it was a bit similar to the current East African prairie, dry and hot." Deng Tao said.
As time passed by 2.5 million years ago, a group of real horses appeared, which was also the fourth dominant animal group to appear in the Linxia Basin.
As the world enters the ice age, the climate in the northwest has become more arid and cold.
"There were a large number of carnivores during this period. They were natural enemies of herbivores. The three-toed horse fauna, which was not as fast as real horses in running and eating, was no longer adapted to the environment at that time." Deng Tao explained that real horses are more similar to modern horses. , Each foot has only one toe, which makes the real horse run faster.
"In Northwest China, the changes in fauna are not only closely related to the global climate, but also affected by the geographical factor of the uplift of the Qinghai-Tibet Plateau." Deng Tao and his team found that there are giant rhinoceros on both sides of the Qinghai-Tibet Plateau. The unearthed fossils indicate that the plateau was far from uplifted to the current height at that time, and the giant rhino fauna could travel freely.
"We speculate that the height of the uplift at that time was below 2,000 meters." Deng Tao said. By the time of the shoveltooth, there was no trace of the distribution of this population on the south side of the plateau, indicating that the plateau had been uplifted to a height that hindered the free migration of the shoveltooth. , "Maybe more than 3000 meters."
It is understood that scientists usually judge the climate and environment at that time based on the distribution of animals, body structure, height of tooth crowns, and food types.
The pollen fossils and spore fossils of some plants can support this judgment.
"The Linxia Basin is a very special area. It is like a'Plateau History Book', which fully records the climate change and the uplift process of the Qinghai-Tibet Plateau in the northwestern region," said Deng Tao.