In order to extract information from millions of years old footprints or fossils, researchers turned into detectives one by one and used various "crime-solving" tricks...
These barefoot footprints are over 10,000 years old!
Let the footprints do the talking
Archaeologists have found some bare foot footprints on rocks inside White Sands National Park in the United States. In ancient times, it was a lake, and these footprints were left on the silt by the lake. When the lake water evaporates, only some minerals remain, eventually forming a footprint. "Some of the footprints were hidden, washed away by the rain, and then disappeared." Matthiew Bennett, a professor in the Department of Environmental and Earth Sciences at the University of Bournemouth in the UK, explains: "To make it visible, we used depth radar. "Radar signals can penetrate the ground and go deep underground, and if a change in soil properties is detected, the signal can return to the surface.
With the help of the device, the scientists involved in the exploration detected human footprints on a 1,500-meter round-trip route, as well as the footprints of prehistoric animals, a ground sloth, a Colombian mammoth, to be exact. As for the year of tracing the footprints, they used the deductive method: on the outbound route, the human footprints covered the animals; On the way back, the animal's footprint covered the human one. Therefore, all these footprints are left at the same point in time. "Given that these species disappeared before the end of the glacier, we infer that these traces are at least 10,000 years old." Matthew Bennett added.
Based on the depth, direction, and size of the footprints, archaeologists determined that the footprints belonged to a small woman. Moreover, due to the different depths of the two footprints, it can be inferred that the woman also has a child beside her. This is how the footprints record a moment at the end of the glacier.
The red material in the center of the amber is actually a small skull.
Ask Amber
American paleontologists have studied an animal skull trapped in amber for 99 million years! The fossilized resin was found in Myanmar's Hukang River Valley. "We got not only the skull of the animal in amber, but also the jaw muscles and part of the tongue." Juan Daza, a biologist at Sam Houston State University in the United States, said. The researchers identified an amphibian, Albanerpetontids, that had disappeared for millions of years.
Researchers have compared the animal's skull with fossil samples from other rocks and believe it belongs to the order Salamander. But it can now be confirmed that the animals in amber belong to a different branch. Thanks to the resin, its hyoid bone and associated muscles have been well preserved. However, "the animal is characterized by a retractable tongue, like a chameleon," Professor Dasa noted. Therefore, it is the first animal to prey on with a telescopic tongue, and some Alban newts are even 165 million years old!
The coral reef-dwelling coral clams help analyze climate change!
See through the texture
Yan Hong's team at the Institute of Earth Environment of the Chinese Academy of Sciences studied the world's largest shellfish, Tridacna gigas, which is mainly distributed in coral reefs in Pacific waters. During its lifetime, it develops many small growth layers, corresponding to its different growth stages. The researchers looked inside the shell with a special microscope and found that whenever extreme weather occurs, such as cyclones, cold snaps, and droughts, the texture and chemical composition of the shells are affected. "When a cyclone passes, the growth rate of shells slows down sharply due to high winds, huge waves, excessive rain, reduced sunlight, etc." Researcher Yan Hong explained.
As a result, it is able to accurately record the drastic changes in the climate: the shell layer can be called a real-time weather broadcast. "We have collected hundreds of large clams on coral reefs in the waters of the South China Sea." Yan Hong said. The researchers used carbon dating on the specimens, confirming that they recorded climate change for a full 5,000 years! Today, Yan Hong's team continues to study in the laboratory, trying to distinguish cyclones, droughts and cold snaps in the past. "By analyzing past extremes like we are analyzing warming, we can predict their future frequency and intensity!" Yan Hong concluded.
The bottom of Thatchpoint Blue Hole holds a valuable climate archive.
Digging into the "loopholes" under the sea
There are sometimes caves on the seabed, which form when the sea level is low, when there is no water in the caves. "There is a sediment buildup inside these caves that the waves cannot wash away." Dr. Tylor Winkler of Texas A&M University (TAMU) explains. Taylor and his colleagues focused on the Thatchpoint Blue Hole in the Bahamas, which has been ravaged by numerous hurricanes in the Atlantic Ocean for 170 years.
To study the sediments in the cave, the team piped deep into the depths of the submarine cave to study the extracts layer by layer. "By carbon dating of the plants contained in the sedimentary layer, the age of each layer can be determined." Taylor Winkler explains. If the leaf fragments are large and numerous, it indicates that a certain number of hurricanes have passed. Large gravel accumulations are also true. Conversely, a build-up of fine sand proves to be a period of calm.
In doing so, the team determined hurricanes at sea for 700 years: between 1500 and 1750, the region experienced multiple hurricanes, far more frequently than in the next two centuries. Based on this study and other undersea caves, researchers will be able to "redraw a detailed map of hurricane activity in the region to observe changes in hurricane activity due to climate change," concludes Taylor Winkler. In short, studying the past can help us better predict the future.
The cave is like a natural ice maker, where ice cubes are formed all year round.
Charcoal from ice
At El Malpais National Monument in the United States, ice blocks in some caves were formed centuries ago. Several geophysicists chiseled through the ice to analyze the charcoal wrapped in it. "The carbon layer is more than 30 centimeters thick and covers several square meters." Bogdan Onac, a geoscientist at the University of South Florida, pointed out.
How are these ice cubes formed? "Rain and snow seep into the cave through surface crevices, freezing as temperatures are below zero all year round. In addition, the entrance of the cave is inclined, and hot air cannot enter, and only cold air with a higher density can enter. "The date of carbon deposition can be determined by carbon dating: this carbon layer is derived from ash formed by burning fires between 150 and 950 AD. At that time, the Pueblo people, the Native Americans, lived here.
So why did these people go to the frozen caves to make fires? "They melt the ice here to get a steady enough amount of drinking water," explains Bogdan Onake, "and in El Malpais, you can only rely on melting snow or a few springs for drinking water. "Because the cave was a precious source of water at the time, there were particularly large amounts of carbon deposited here during three special drought periods." We know this by studying tree rings in the area," Bogdan Onak adds, "If the rings are thin, it means that there is not enough rain in the corresponding year. "So the carbon particles in the ice can support the dry period, and also show the wisdom of human response to climate change."
Year rings help determine the year in which anomalies in the atmosphere occurred.
Count the annual rings
Robert Brakenridge, an earth scientist at the University of Colorado, has been focusing on supernovae. A supernova is a violent explosion that some stars experience near the end of their evolution. He speculates that the closest supernova to Earth could lead to an increase in carbon-14 on Earth. To this end, he paid special attention to the field of supernovae and learned that the carbon-14 content in some tree rings was abnormal.
To do this, Brackenridge compared the relevant year-ring data with all known supernova information. Under normal times, atmospheric carbon-14 production remains stable. "However, the high-energy radiation released by supernovae can reach Earth, producing large amounts of carbon-14." Robert Brackenridge explains. So, he studied several periods of dramatic increases in carbon-14 content in tree trunks and found that from 12740 BC to 5340 BC, the four peaks of carbon-14 content in tree rings correspond to four supernovae.
Still, "there is a great deal of uncertainty about the age and distance of these supernovae," Robert Brackenridge cautions, adding, "it's possible that giant solar flares are responsible for this effect." Regardless of future research results, the very fact that trees record cosmic phenomena embodies the perfect combination of botany and astronomy.
Homo sapiens' distant relative, Homo sapiens, was born in the Olduvai Gorge.
Listen to bacterial testimonials
One of the cradles of human civilization is located in the Olduvai Gorge in Tanzania. It is a semi-arid region where modern humans lived 1.5 million years ago. In the area, archaeologists take samples from two strata that are between 1.7 million and 1.8 million years old, looking for traces of biomass (plants, microorganisms, etc.). By chemically analyzing the extracted samples, they discovered a polarophilic bacterium, Thermocrinis ruber. They are invisible to the naked eye but can bring important information about the past of Olduvai Canyon. "The bacteria can only be detected in special environments with high water temperatures, such as hydrothermal sources." Spanish geologist David Martín-Perea noted.
Today, they can be found in hot springs in Yellowstone National Park in the United States. This means that in the age of the able, the Olduvai Gorge was a hot spring area. That's right, even such simple microbes can reveal an overview of a prehistoric landscape!
Written by Emmanuel Deslouis
Compiled by Wu Sumei
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