"When doing paleontological research, you especially need to be able to sit on the bench." said Yin Zongjun, a researcher at the Nanjing Institute of Geology and Paleontology, Chinese Academy of Sciences. For more than ten years, he has been focusing on this unpopular subject, hoping to uncover the hidden history of animal evolution behind fossils. This persistence comes from love, as well as from the progress of scientific research and the support of the institute.
Tiny fossils with a diameter of about 1 mm were carefully separated from the rocks and placed under a microscope for three-dimensional scanning using ultra-high-resolution X-ray microtomography. The three-dimensional structure is reconstructed on the display. Based on this analysis, the animal evolutionary history hidden behind the fossils can be revealed.
This is the daily work of Yin Zongjun, a researcher at the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences. The research team led by this 35-year-old young scientist used the latest three-dimensional non-destructive imaging technology to scan more than 300 rotifer fossil specimens, showing that there is cell division inside the rotifer - this development method is similar to that of early animal embryos. Development is very similar. "The 600-million-year-old Weng'an spinworm is an ancient close relative of modern animals." He recently came to this conclusion in a paper published in Science Advances, a subsidiary magazine of Science.
"This is my preliminary answer to 'Darwin's Dilemma'." Yin Zongjun said. He is short in stature, has an active mind, and speaks very fast. The slogan "Self-discipline gives me freedom" is printed on his sweater, which is very similar to his usual style of conduct. For more than ten years, this research and his dream have never stopped.
Passionate and obsessed with the mystery of the origin of animals
In 2006, Yin Zongjun, a junior student at China University of Geosciences (Wuhan), gave up his postgraduate admission qualification and chose to take the postgraduate entrance examination - to the Chinese Academy of Sciences Nanjing The Institute of Geology and Paleontology, the national paleontological research highland, launched an attack.
Why are you so determined? This is related to the research path he set for himself. Yin Zongjun grew up in the Dabie Mountains. His sister gave him a set of "Natural Encyclopedia for Primary School Students". "This set has 6 books. I like "Earth Science" and "Animals" the most. One talks about rocks, minerals, and famous mountains on the earth. Dachuan, a book about ancient animals and the birth of human beings, I couldn’t put it down and quickly turned over the book,” said Yin Zongjun.
Isn’t it the intersection of geoscience and zoology that is paleontology? Looking back many years later, he realized that the seeds of science had been quietly planted in his heart at that time.
When taking the college entrance examination, Yin Zongjun applied for the geology major. Senior brothers and sisters said that undergraduates majoring in geology are the most popular and have "money prospects", but instead they go on to study for master's or doctoral degrees in paleontology, which is becoming increasingly unpopular. But Yin Zongjun decided early to go to graduate school. He learned in class that Darwin once mentioned a difficult problem that challenged the theory of evolution: the ancestors of most modern higher animals suddenly appeared in the strata in the form of a large explosion during the early Cambrian period 541 million to 518 million years ago. , this phenomenon was later called the "Cambrian Explosion of Life"; however, in the long history of the earth before the Cambrian, there was a lack of fossil records related to animals.
Darwin’s explanation for this is the incomplete preservation of fossil records. Animals before the Cambrian may not have left any fossil records. This explanation caused great controversy over the next 100 years and was known as "Darwin's Dilemma." "More than 100 years have passed, why is 'Darwin's Dilemma' still a mystery?" Yin Zongjun's goal for himself is to become a scientist and explore the boundaries of knowledge.
Delve into the biological codes in tiny fossils
With questioning, Yin Zongjun came to Nangu Institute for graduation project. The target he chose was the Weng'an biota.
The Weng'an Biota is mainly produced in the phosphorus-bearing strata of the Beidou Mountains in Weng'an, Guizhou. It preserves fossils 600 million years ago through phosphate formation and was born before the Cambrian explosion. Therefore, this fossil library, which may contain the oldest animals in the world, is regarded by academic circles as "the dawn of the animal world."
"In the summer of 2006, I collected hundreds of kilograms of stones from Beidou Mountain, packed them and sent them to Nanjing, searching for fossils like a needle in a haystack." In Yin Zongjun's memory, that summer was very hot, so he first used chemical methods to separate several Hundreds of kilograms of rocks were melted, and fossils were found bit by bit in the residue and observed with a microscope. I didn't dare to turn on the fan because I was afraid that the stone residue would be blown away by the wind.
Finally, Yin Zongjun found a large number of fossils that he had never seen before. One of the fossils is very special. It has a diameter of less than 1 mm, looks like a modern animal embryo, and has spiral coils on its surface. This is the fossil that was later called the "Weng'an Spiral Worm" fossil.
Observing and analyzing the morphological structure of newly discovered fossils through microscopes and scanning electron microscopes is enough to complete your graduation thesis. But what is the structure inside the mysterious fossil? Are they animals, plants, or algae? These still need to be studied in depth.
"I want to engage in research that interests me, and there is only one way to go to the end." Yin Zongjun said. In the second year of his master's degree, he was selected and given the opportunity to study directly for a doctoral degree.
These fossil specimens were so tiny that the thinnest blades of the time were thicker than they were. If you want to reproduce the internal structure, you need to use professional equipment like CT scanners in hospitals. At that time, Europe had the most advanced synchrotron radiation accelerator in the world, which could scan the internal structure of objects at the micron level. During his PhD studies, Yin Zongjun applied to study in France, taking thousands of samples with him to explore the biological codes in small fossils.
But even with the equipment, "doing CT" is not easy. This large-scale scientific device is not tailor-made for scanning microfossils. Therefore, when used to "do CT" for microfossils, the scanning method and many parameters must be repeatedly explored and adjusted. For example, if the light source setting is too weak, the signal cannot penetrate, and if it is too strong, it will easily be overexposed.
"It took me several months of study to master the scanning technology. Unfortunately, the Weng'an Spiralis fossils have very thick capsules, and most of the internal structures are rotten, and the internal structures were not scanned in all samples. , so there is no way to know what it is. "Fortunately, Yin Zongjun also gained other things while studying abroad: by scanning other samples he brought, he discovered the earliest sponge animals and the earliest embryonic fossils...
These. Research is still a long way from answering "Darwin's Dilemma". "We can't go all the way to Europe every time and use other people's machines to scan fossils." Yin Zongjun began to think about having advanced technology and letting his team "do CT" for fossils.
Innovation, let cutting-edge technology help ancient disciplines
It is not realistic to "move" the advanced synchrotron radiation accelerator back. There is no other way but to rely on innovation.
With the support of the Nangu Institute, after graduating with a PhD in 2012 and staying at the institute, Yin Zongjun set out to establish a fossil micro-CT laboratory, which was completed in 2015. Walking into this laboratory, you will find all kinds of instruments and equipment: in terms of hardware, there are "CT machines", microscopes, graphics workstations, and digital screens; in terms of software, there are various professional image data processing and three-dimensional visualization tools. It is not only used for the study of Weng'an biota fossils, but also supports research on insect diversity in amber, the origin of forests and other paleontological topics.
"This laboratory has original innovation and integrated innovation." Yin Zongjun said that the patent-pending multi-sample scanning technology is an independent innovation. "Manually placing the samples one by one on the sample stage for scanning is time-consuming and labor-intensive. If automatic and uninterrupted scanning can be realized, it can help scientific researchers free up their hands and greatly improve the efficiency of equipment utilization." Yin Zongjun said that cutting-edge information technology and this ancient discipline Can create sparks. He sets parameters and programs through software so that the sample stage not only "knows" the scanning time and method of each sample, but can also "find" the next sample in line and "invite it to the stage."
In June last year, a breakthrough was made in the research on the Weng'an Spiralis fossils. After analysis of the internal structure and biological information of the fossils, it was confirmed that they are single-celled life and belong to the "sister group" of animals. "Based on this, we can understand the biological information of the common ancestors of animals, which provides important fossil information for understanding where the first animals came from.
"When doing paleontological research, you especially need to be able to sit on the bench. The reason why I can persevere is not only my own love, but also the unconditional support of the institute and the progress in the research process. Let young scientists show off their talents at the initial stage and taste the joy of success." Yin Zongjun said that the truth of animal evolution is gradually emerging, and "Darwin's Dilemma" will one day be completely solved.