Evidence has been 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 appeared on Earth 635 million years ago, presenting findings that show life could have existed more than a billion years earlier.
In a study published Monday in Precambrian Research by scientists at Cardiff University in Wales, the researchers found environmental evidence that complex life existed 1.5 billion years earlier than previously thought, but failed to “spread” globally.
This evidence, according to the study authors, could suggest a “two-step” evolution toward 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, the study said.
“The availability of phosphorus in the environment is considered a key element in the evolution of life on Earth, particularly in the transition from simple single-celled organisms to complex organisms such as 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 Archean blocks that were once part of a single landmass in central Africa and eastern Brazil, Fru said.
“We believe that submarine volcanoes, which followed the collision and suture of the Congo and São Francisco cratons into a single 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.
Researchers believe the underwater volcanic environment paved the way for “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 within the scientific community, according to Fru, who believes the study’s findings could answer questions surrounding the fossils’ origins.
“This would have provided enough energy to promote increased body size and more complex behavior seen in simple, animal-like primitive life forms, such as those found in fossils from this period,” Fru said.
However, according to the study, these complex life forms did not spread globally from the “restricted nature” of the underwater region and eventually became extinct.
“While the first attempt failed to propagate, the second gave rise to the animal biodiversity we see on Earth today,” Fru said.
