Life on Earth may have started 1.5 billion years earlier than previously thought, according to new evidence discovered by a group of scientists.
According to a report by the BBC, researchers working in Franceville, Gabon have discovered evidence in rocks that indicate the environmental conditions for possible life forms existing 2.1 billion years ago.
But scientists noted that the findings of these potential life forms were limited to an inland sea, did not spread globally, and eventually died out.
This theory challenges the prevailing view among scientists, who generally estimate that animal life began around 635 million years ago. The new research contributes to an ongoing debate over whether so-far unexplained formations found in Franceville, Gabon are actually fossils or not.
The scientists examined the rock around the formations for evidence of nutrients such as oxygen and phosphorus that could have sustained life.
Prof. Ernest Chi Fru from Cardiff University was involved in the research team and told BBC News that if the theory is accurate, these life forms would be similar to slime mold, a brainless single-cell organism that reproduces with spores.
However, not all scientists are convinced. University College London Professor Graham Shields, who was not involved in the study, is a sceptic of the theory.
"I'm not against the idea that there were higher nutrient levels 2.1 billion years ago, but I'm not convinced this would have led to complex life," he said, calling for more evidence to support the claim.
Chi Fru argued that his research provides insight into the processes that create life on Earth.
"We're saying, look, there's fossils here, there's oxygen. It's stimulated the appearance of the first complex living organisms," Fru said.
"We see the same process as in the Cambrian period 635 million years ago. It helps back that up. It helps us understand ultimately where we have all come from."
The initial hint of earlier complex life emerged a decade ago with the discovery of the Francevillian formation. Prof. Fru and his colleagues said the formation contained fossils indicating evidence of life capable of self-movement and wiggling. But the findings were not accepted by all scientists.
To further their investigation, Chi Fru and his team analyzed sediment cores from the rock in Gabon, revealing that the chemistry of the rock is indicative of a "laboratory" for life formed just before the formation appeared.
Scientists believe that high levels of oxygen and phosphorus resulted from volcanic activity triggered by the collision of continental plates underwater, which created a nutrient-rich shallow inland sea.
Chi Fru also said that this protected environment created ideal conditions for photosynthesis, resulting in significant oxygen levels in the water.
"This would have provided sufficient energy to promote increases in body size and greater complex behavior observed in primitive, simple animal-like life forms such as those found in the fossils from this period."
Fru also noted that the isolated environment also led to the demise of the life forms due to a lack of new nutrients to sustain the food supply.
