Complex life forms existed 1.5 billion years earlier than previously believed, study finds
Evidence was found in marine sedimentary rocks near Gabon in Central Africa.
A team of international researchers has challenged the long-held belief that complex life forms first emerged on Earth 635 million years ago, presenting findings that show life may have existed over a billion years earlier.
In a study published in Precambrian Research Monday by scientists from Cardiff University in Wales, researchers found environmental evidence that complex life existed 1.5 billion years earlier than previously believed but failed to "spread" globally.
This evidence, according to the study's authors, could suggest a "two-step" evolution to complex life on Earth.
The evidence was found in marine sedimentary rocks from the Franceville Basin near Gabon in Central Africa, which experienced an episode of underwater volcanic activity from two Precambrian continents, or cratons, colliding 2.1 billion years ago, according to the study.
"The availability of phosphorus in the environment is thought to be a key component in the evolution of life on Earth, especially in the transition from simple single-cell organisms to complex organisms like animals and plants,” Dr. Ernest Chi Fru, lead author of the study from Cardiff University's School of Earth and Environmental Sciences, said in a press release Monday.
The two Precambrian cratons examined in the study are the Congo and São Francisco cratons, which were stable Archaean blocks that were once part of a single landmass in central Africa and eastern Brazil, according to Fru.
“We think that the underwater volcanoes, which followed the collision and suturing of the Congo and São Francisco cratons into one main body, further restricted and even cut off this section of water from the global ocean to create a nutrient-rich shallow marine inland sea," Fru said in the press release.
The researchers believe that the underwater volcanic environment led the way to "cyanobacterial photosynthesis," which created a "generation of a large food resource" to enable the formation of complex life.
Large macroorganism fossils from this period have been the subject of debate by the scientific community, according to Fru, who believes the study's findings may answer questions surrounding the fossils' origins.
"This would have provided sufficient energy to promote an increase in body size and greater complex behaviour observed in primitive simple animal-like life forms such as those found in the fossils from this period,” Fru said.
The complex life forms, however, did not spread globally from the "restricted nature" of the underwater region and eventually died out, according to the study.
"While the first attempt failed to spread, the second went on to create the animal biodiversity we see on Earth today," Fru said.