All complex life on the earth today is multicellular eukaryotes, and the multicellularization of eukaryotes is a necessary condition for the evolution of life to complexity and large-scale, which is considered to be one of the major events in the history of life evolution. However, when does eukaryotes become multicellular? When did multicellular eukaryotes start appearing on Earth? So far, there is no clear answer to this major scientific question.
On January 25, the "Early Evolution of Earth-Life System" team led by Zhu Maoyan, a researcher at the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, published the latest research results in Science Advances: the team 16Fossils of multicellular eukaryotes have been found in strata 300 million years ago. This follows the discovery in 2016 in the Yanshan areaAfter the world's earliest macro-multicellular eukaryotic fossil 600 million years ago, the team made another important breakthrough in the field of early life evolution, further advancing the emergence of multicellular eukaryotes by about 70 million years, making it the earliest fossil record of multicellular eukaryotes discovered in the world so far.
Back in 2016, Zhu Maoyan's team reported on the Yanshan area in Nature Communications15600-million-year-old fossil of macro-body multicellular eukaryotes. This discovery not only advanced the emergence of large multicellular eukaryotes on Earth by nearly a billion years, but also deduced that eukaryotes should have become multicellular earlier.
In order to demonstrate this inference, the team has collected hundreds of Great Wall shale samples at multiple cross-section sites in the Yanshan area over the past eight years, and obtained a large number of microfossil specimens through experimental processing. A total of 278 fossil specimens were found in this batch, which are unbranched filaments composed of a single row of cells, which are similar in shape and size to the fossils of "Magnificent Qingshan Algae" previously reported by other researchers in the shale sections of the Chuanlinggou Formation in central Yanshan, and are classified into the same genus and species in this study.
Previous researchers have interpreted these fossils as primitive green algae, perhaps because the fossils are not clear and the evidence of biological interpretation is insufficient, so they have not attracted the attention of domestic and foreign counterparts since they were reported in 1989. The study found that some of the cells of Magnificent Qingshan contain circular structures with a diameter of about 15 to 20 microns, which is interpreted as a kind of reproductive cell. It can be seen that Magnificent Aoyama algae is an organism that reproduces through spores.
In this study, we made a comprehensive comparison of the morphological complexity, cell size, and reproduction mode of filaments, and found that there is no comparable type in prokaryotes, while there are many filamentous organisms in eukaryotes that resemble magnificent green algae. Therefore, the research team believes that the S. magnificus should be a multicellular eukaryotic fossil. Comprehensive analysis showed that the morphology, cell size distribution and reproduction mode of some surviving green algae were the closest to those of Magnificent Qingshan algae. Therefore, the research team believes that it is not only a multicellular eukaryotic organism, but also probably has the metabolic ability of photosynthesis and belongs to the multicellular algae, although it is currently impossible to attribute it to a specific living phylum.
In order to further verify the eukaryotic properties of Algae magnificia, the research team conducted a spectroscopic analysis of the organic matter composition of Algae magnificia, and the results showed that the organic matter composition of Algae magnificus was significantly different from that of cyanobacterial fossils, which supported the explanation that it was classified as a multicellular eukaryotic organism.
The earliest fossil record of eukaryotes, which is generally accepted by the academic community, was found about 16 years agoIn the Late Paleoproterozoic strata 500 million years ago, this study found that the appearance of Magnificent Qingshan algae was only slightly later than these oldest single-celled eukaryotic fossils, indicating that the emergence of eukaryotes was followed by a rapid complex multicellular evolution.
If Magnificent Qingshan algae can be identified as a eukaryotic algae that are photosynthesizing, then the last common ancestor of eukaryotes should be no later than 16The Late Paleoproterozoic period 300 million years ago is nearly 600 million years earlier than the time generally accepted by the current academic community, and it is basically consistent with the time estimated by the molecular clock. According to Zhu Maoyan, this study provides new thinking for further revealing the mystery of the origin and early evolution of complex life and the evolution of the Earth's environment in the Proterozoic.
*:Light**.