All complex life known to humans on Earth today are multicellular eukaryotes. When did eukaryotes first become multicellular? When did multicellular eukaryotes begin to appear on Earth? According to news from the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, on the 25th, a scientific research team from the institute discovered a 1.63 billion-year-old multicellular eukaryotic fossil, which is also the oldest multicellular eukaryotic fossil discovered so far.
Relevant research results were published in Science Advances, a sub-journal of the American magazine Science.
In 2016, the scientific research team of the institute discovered 1.56 billion-year-old macrobody multicellular eukaryotic fossils in the Yanshan area. Zhu Maoyan, a researcher at the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, said: "This discovery advances the emergence of large multicellular eukaryotes on Earth by nearly 1 billion years from the previously thought 600 million years ago. From this, we infer that eukaryotes should have become multicellular earlier."
In order to prove this inference, Miao Lanyun, a member of the team, collected hundreds of samples from strata 1.6 billion years ago in the past eight years, and finally discovered microscopic multicellular eukaryotic fossils.
Miao Lanyun said that there are 278 fossil specimens discovered in this batch. They are unbranched filaments composed of single rows of cells. The maximum length of filaments is 860 microns. The overall structure is relatively simple, but shows a certain degree of complexity. Some filaments shrink uniformly toward one end, and the cells are columnar, barrel-shaped or cup-shaped. In particular, in some specimens, reproductive spore structures were found. Comprehensive analysis and comparison of various characteristics and components of the fossils indicate that these fossils belong to multicellular eukaryotes.
"By measuring two ratios that can characterize changes in filament morphology and the distribution frequency of filament diameters, we found that these filaments showed continuous transition and change in morphology, which indicates that they belong to the same species. At the same time, these filaments are similar in shape and size to the 'Magnificent Qingshan Alga' fossil found in the Yanshan area, so this study classified them into the same genus and species," said Miao Lanyun.
According to reports, the earliest fossil record of eukaryotes that is currently generally accepted by the academic community was found in the late Paleoproterozoic strata in North China and northern Australia about 1.65 billion years ago. "Magnificent Green Mountain Alga" appeared only slightly later than these oldest single-cell eukaryotic fossils, indicating that much more complex cellular evolution quickly occurred after the emergence of eukaryotes.
"If 'Magnificent Green Mountain Alga' can be confirmed to be a photosynthetic eukaryotic algae, then the last common ancestor of eukaryotes should be no later than the late Paleoproterozoic 1.63 billion years ago, which is nearly 600 million years earlier than the time generally accepted by the current academic community." Zhu Maoyan said that this provides new thinking for further revealing the origin and early evolution of complex life, as well as the evolution of the Earth's environment in the Proterozoic.