Decimetre-scale multicellular fossils from the 1.56-billion-year-old rocks of North China (picture by ZHU Maoyan)
New fossils discovered in North China suggest that life "went large" on Earth more than 1.5 billion years ago, or nearly one billion years earlier than previously thought. This research has been published on Nature Communications on May 18, 2016.
According to Prof. ZHU Maoyan from NIGPAS and his colleagues, these 1.56-billion-year-old, macroscopic multicellular eukaryotes fossils are preserved as carbonaceous (carbon-rich) compressions up to 30 cm long and 8 cm wide, which are discovered in the mudstone of the Mesoproterozoic "Gaoyuzhuang Formation" in the Yanshan region, Hebei Province, North China. Among the total 167 measurable fossils, 53 exhibit at least four regular shapes (linear, cuneate, oblong and tongue-shaped). Organic fragments extracted by acid maceration from the host rocks of the macroscopic Gaoyuzhuang fossils show extraordinarily well-preserved multicellular cell structure. Based on the morphometric analyses of these macrofossils and syngenetic cellular microfossils, authors interpret these Gaoyuzhuang fossils as benthic, multicellular and likely photosynthetic eukaryotes with unprecedentedly large size and a modest diversity populated in early Mesoproterozoic seas. However, their exact affinity remains uncertain. Further research will help to shed light on the ancient marine ecosystems.
Before the discovery of the Gaoyuzhuang macrofossils, eukaryotes with comparable size were not known in the fossil record older than the ca. 600 million years Ediacaran seas. So, this new discovery predates the diversification of macroscopic multicellular eukaryotes by nearly 1,000 million years. The Gaoyuzhuang macrofossils represent the compelling evidence for the early evolution of organisms large enough to be visible with naked eyes, and completely renew the current knowledge on early history of life written in textbook that the oldest known macroscopic organism is Grypania, a coiled and ribbon-like fossil smaller than two millimeters wide and a few centimeters long during the early Proterozoic. Therefore, the discovery provides a crucial benchmark for our understanding of early evolution of eukaryotes, and stimulate new thinking on the Proterozoic Earth-life system which has been called as the "Boring Billion" or "Earth’s middle age" exhibiting evolutionary stasis.
The research project was supported by the National Natural Science Foundation of China, the Ministry of Science and Technology of China, the China Geological Survey, and the NASA Astrobiology Institute.