The Chinese team lasted 30 years of science, ending a cross -century debate

Author:Scientific network Time:2022.07.10

Text ｜ "China Science News" reporter Shen Chunlei

In 1991, Hou Xianguang found Yunnan worm fossils in Chengjiang Mai Tianshan, Chengjiang, Yunnan. At that time, he was a researcher at the Nanjing Institute of Geological Palace (hereinafter referred to as the Nanjing Paramantual Institute) of the Chinese Academy of Sciences.

Through fossil research, Chinese scholars speculate that Yunnan worms may be the earliest vertebrate. Subsequently, this view set off a cross -century question and argument in the international academic community.

Today, this cross -century argument can finally be concluded. The research team of my country's scientific research team found that the Yunnan worm produced by the Cambrian Ji Chengjiang animal group before 518 million has the unique cell cartilage structure of vertebrates, and then confirmed that Yunnan worms are the most primitive group of vertebrates. Related research results were published on July 8th in Science.

The result was completed by Zhu Maoyan team of Nanjing Poto Institute and Jiang Baoyu, a professor of Nanjing University, and Jiang Baoyu. Researcher Zhao Fangchen and Jiang Baoyu of Nanjing Potorate Institute of Poor Bio are the author of the dissertation. The doctoral student of the two was the first author. This is also Tian Qingyi's first science.

The origin of controversy

Evolutionary biologists usually speculate that the ancestors of vertebrates are a type of rear animal with spine, dorsal neurotrants and gill fissures based on the characteristics of the characteristics of the existing head cable. However, this false imagination has never been supported by fossil evidence.

In 1909, foreign researchers discovered the Burgis shale animal group, Canada, which is about 505 million years ago, and then produced a cord animal pickup fish and base trunk vertebrates.

Since 1991, in the Chengjiang Animal Group, China, which is about 518 million years ago, scientific researchers at the Nanjing Potorate Institute have discovered a variety of spine animals, including Kunming fish and doubtful Yunnan insects in the cadres.

These fossils are the oldest spine animals in the world so far, providing precious materials for the mysteries of the origin and early evolution of vertebrates.

"Spine animals include tails, head cable animals, and vertebrates." Zhao Fangchen told the China Science Journal, "Unlike Kunming fish with typical vertebrate characteristics, Yunnan worm form is closer to the head cablewood Wenchang fish. The location of the animal origin and the rear animal system has always been controversial. "

Yunnan worm fossils were first discovered by Hou Xianguang in Chengjiang Mao Tianshan, Chengjiang, Yunnan. In 1995, according to the newly collected Yunnan worm fossils, Chen Junyuan, a researcher at the Nanjing Paramountry Institute, published a paper on Nature.

Yunnan insect specimen, 3.9 cm long (Zhao Fangchen's picture)

Yunnan worm ecological restoration map (directed by Zhao Fangchen, Yang Dinghua drawing)

After the thesis was published, the New York Times and Science Weekly made special comments on the title of "From Yunnan Worm to You" and "Road to the Bone Bone".

Because the Tianshan fossil site was protected at the time, it was difficult to dig, so Chen Junyuan turned his eyes to Haikou Town, Kunming, Kunming, several tens of kilometers. There are sedimentary rocks in the same age as Mattians, and there are most likely a large number of fossils.

Sure enough, Chen Junyuan and others found a large number of new Yunnan worm specimens in the Haikou area of Kunming. They carried out a more fine anatomy structure on these specimens, and on the basis of this research, the Yunnan worm was attributed to the original type, and it believed that its evolution position was between the head cablewood and vertebral eels.

After the above results were published in Nature in 1999, a major discussion on the classification of Yunnan worm was set off in the academic world.

Different scholars have large differences in the interpretation of the details of Yunnan insects to preserve different software tissue. Since the first report of Yunnan worms, it has been classified as vertebrates, head cable animals, semi -cable animals, rear animals, and even the original symmetrical animals.

Zhao Fangchen pointed out that due to the controversy in the classification position of Yunnan insects, the research on the origin of vertebrates based on such key fossils was seriously affected.

127 specimens revealed the secrets from the micro

In 2018, Tian Qingyi began to engage in research related to Yunnan insects. He found that there were many research papers in Yunnan worms, at least 20 to 30 articles. The research level of each paper was high.

He told the Journal of China: "Almost most of the macro structures have been repeatedly described and studied by the predecessors. No breakthrough point. "

In response to the mystery of Yunnan insect classification positions, since conventional morphological research cannot reach consensus, through repeated communication and discussions with mentor Zhao Fangchen and Jiang Baoyu, Tian Qingyi decided to start from the micro structure. "We use a three -dimensional X -ray fault scanning microscope, Fourier infrared spectrum, Raman spectrum, scanning electron microscopy and transmitted electron microscopy. We hope to start with a micro anatomy structure to crack this mystery."

In 2003, Chen Junyuan and his collaborators proposed that Yunnan's gill bow may have cell cartilage. "According to this important clue, we analyzed the gill bow structure of 127 Yunnan worm specimens produced in Haikou area, and for the first time, the three -dimensional stacked cell structure and protein were found on the Yunnan worm's swallow bow. The micro -original fiber structure. "Tian Qingyi introduced.

It is these two characteristics that it proves that Yunnan insects have vertebrates unique and composed of cell cartilage, which indicates that Yunnan worms are primitive vertebrates.

Further research results have confirmed that Yunnan worms are in the most foundation of the vertebrate spectrum, between tails and other vertebrates (including existing and fossil species).

Comparison of Yunnan insect evolution positions and various ridge animal throat shapes (from top to bottom, namely Wenchang fish, Yunnan worm, Hou Sprig fish, sedimental eel, shark) (A) evolved tree and throat morphological patterns distributed.绝 Symbol represents the extinction group (B) side view (C) abdominal view. (Tian Qinghuan's drawing)

For the first pair of swallowed bows that were previously controversial in Yunnan worms, in the position of the new specimen equivalent to the first pair of swallow bows, the research team discovered the structure, gill filament and protein like other gill bows in the rear gill bow. The structure of micro -original fiber. The research team determined that Yunnan worms have 7 pairs of swallow bows with similar to each other and have cell cartilage.

Similar swallow bows also appeared on another type of Cambrian Condroma -Hou Spirge Fish.

As early as the 19th century, anatomists had proposed the theoretical hypothesis of vertebral animal pharyngeal bow, and the discovery of the 7 -pair of throat bows similar to the Yunnan worm supported this hypothesis. That is, the gill bow of fish is the prototype of the jaw bow and the tongue bow. The jaw bow and the tongue bow of the vertebrates and the gill bow behind are the series of homologous structures.

Tian Qingyi explained that although the swallow bows in different positions in the existing vertebrates will develop into different skeletons such as jaw arches, tongue bows, and gill arch, but in the early days of vertebrate evolution, pharyngeal bows in different locations are similar to each other.

Yunnan wormworm fossil pharyngeal structure (A) overall photo of the pharynx; (B -E) micro -structure of pharynx arow: optical photo of the pharynx bow: (B) structural schematic diagram (C) a three -dimensional X -ray CT rendering of a single pharynx (D) ) Scanning electron microscopy photos of carbon residues in the swallow bow, showing the protein micro -original fiber morphological structure of the fossil (E) (Tian Qinghuan diagram)

"This is a milestone work"

After the research papers of Sprigyu in 1993, scientific researchers finally discovered the head of vertebrates through the research of about 100 new specimens. In 2014, it was identified as vertebrates; Published, scientific researchers conducted a micro -scale research on 127 specimens, and in 2022, they were identified as primitive vertebrates.

Why do I need to be determined as vertebrates for so long? Tian Qingyi explained: "Because Yunnan worms have always lacked the macro characteristics of vertebrates that are generally recognized, today, with cutting -edge analysis techniques decades later, we finally found key micro -characteristics."

"Many lives on the planet have not been preserved, and we are lucky because we have found the evidence of life -fossils." Zhao Fangchen hopes that Tian Qingyi, who is visiting the United Kingdom, can use our natural fossil treasure troves while opening up his horizons to do it. More cutting -edge research.

"This Science paper not only identified the oldest close relative of the live vertebrates, the Yunnan worm, but also provided key evidence for revealing the origin and early evolution of vertebrates. The far -reaching influence. "Zhu Maoyan pointed out that from another perspective, the study once again showed the potential of the sophisticated biological structure of the Chengjiang animal group.

The reviewer gave a high evaluation of the study: "This is a major contribution to science, and it will become a key papers in ancient vertebrate zoology, showing the long -awaited, most credible and most credible anatomical structure fossil evidence evidence , Solving the problem of vertebrates of Cambrian Ganzan Group. In the future many years, it is difficult to surpass even higher resolution research. This is a milestone work. "

Related thesis information:

https://www.science.org/doi/10.1126/science.abm2708.

edit |

Capture | Guo Gang

/> />