Scientists have widely accepted that complex life first appeared on Earth around 635 million years ago (during the Ediacaran Period). However, an international team of paleontologists from Cardiff, Toulouse and Poitiers universities and China Nonferrous Metals (Guilin) Geological Mining Co., Ltd. has discovered evidence of a much older ecosystem more than 1.5 billion years ago in the Franceville Basin near Gabon on the Atlantic coast of Central Africa.
Artist's impression of a lobe-like macrofossil that lived in a shallow inland sea formed by the collision of two continents 2.1 billion years ago. Image by Abderrazak El Albani, University of Poitiers.
“The availability of phosphorus in the environment is thought to have been a key factor in the evolution of life on Earth, particularly in the transition from simple single-celled organisms to complex organisms such as animals and plants,” said Dr Ernest Chi-Ful, from Cardiff University.
“We already know that elevated marine phosphorus and oxygen concentrations in seawater are linked to an evolutionary event about 635 million years ago.”
“Our study adds an even older event to the record, going back 2.1 billion years.”
Scientists have widely debated the validity of the fossils of megafauna from the Ediacaran period, the oldest of their kind in the geological record.
But Dr Chi Hulu and his colleagues identified a link between changes in the environment before their emergence and increased nutrients, which may have triggered their evolution.
Geochemical analysis of marine sedimentary rocks dating back 2.1 billion years has shed new light on this unusually large fossil assemblage in the Franceville Basin.
A 2.1 billion year old lobe-like macrofossil from the Franceville Basin. Image by Abderrazak El Albani, University of Poitiers.
“We think that after the Congo and San Francisco cratons collided and sutured together, undersea volcanoes further restricted water in this area and even cut it off from the global oceans, forming a nutrient-rich shallow inland marine sea,” Dr Chi-Hulu said.
“This created a localized environment of abundant cyanobacterial photosynthesis for extended periods, leading to oxygenation of local ocean waters and the generation of large food resources.”
“This would have provided enough energy to fuel the increased body size and more complex behaviors seen in the primitive, simple animal-like life forms found in fossils from this period.”
However, the restricted nature of this body of water, combined with the harsh conditions that existed beyond this environmental boundary for billions of years afterward, likely prevented these enigmatic life forms from colonizing the entire planet.
The study suggests that these observations may indicate a two-stage evolution of complex life on Earth.
Step 1 followed the first significant increase in atmospheric oxygen content 2.1 billion years ago, and step 2 followed a second increase in atmospheric oxygen levels about 1.5 billion years later.
“While the first attempt failed to catch on, the second attempt led to the creation of the diversity of animals seen on Earth today,” Dr Chi Hulu said.
of result Published in the journal Precambrian Studies.
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Ernest Chi-Ful others2024. Hydrothermal seawater eutrophication triggers a localized macrobiological experiment in the 2100 Ma Paleoproterozoic Franceville Subbasin. Precambrian Studies 409: 107453; doi: 10.1016/j.precamres.2024.107453
Source: www.sci.news
