Scientists claim to have unearthed evidence suggesting complex life on Earth may have existed 1.5 billion years earlier than previously thought. A team working in Gabon, Central Africa, discovered traces in ancient rocks that indicate conditions suitable for animal life as far back as 2.1 billion years ago.
However, these early life forms appear to have been confined to an inland sea and didn't spread globally, eventually dying out. This radical notion, significantly earlier than the commonly accepted 635 million-year-old emergence of animal life, has sparked debate among the scientific community.
The research focuses on the Francevillian Formation, a source of ongoing debate surrounding the potential presence of fossils. The team examined the surrounding rocks for signs of nutrients like oxygen and phosphorus, crucial for supporting life.
Professor Ernest Chi Fru of Cardiff University, leading the international team, suggests that these early life forms resembled slime moulds, simple single-celled organisms that reproduce via spores.
While intrigued by the findings, Professor Graham Shields of University College London, who was not involved in the study, expressed reservations. He acknowledged the potential presence of higher nutrient levels 2.1 billion years ago but questioned whether this could lead to the diversification needed for complex life, urging for further evidence.
Professor Chi Fru maintains that his research sheds light on the processes driving the emergence of 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," he 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 early complex life emerged ten years ago with the discovery of the Francevillian Formation. Professor Chi Fru and his colleagues interpreted it as evidence of life forms capable of independent movement. While not universally accepted, this discovery sparked further investigation.
To solidify their findings, the team analyzed sediment cores drilled from the Gabonese rocks. The chemical composition of the rock revealed a "laboratory" for life, created shortly before the formation itself.
This "laboratory", they suggest, was a result of two continental plates colliding underwater, triggering volcanic activity. The collision isolated a section of water, creating a nutrient-rich, shallow inland sea.
Professor Chi Fru believes that this isolated environment provided the ideal conditions for photosynthesis, leading to a significant increase in oxygen levels within the water. "This would have provided sufficient energy to promote increases 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," he explained.
However, this protected environment ultimately led to the demise of these early life forms. The lack of new nutrients entering the isolated sea resulted in a dwindling food supply.
Elias Rugen, a PhD student at the Natural History Museum not involved in the research, agrees that "oceanic carbon, nitrogen, iron and phosphorus cycles were all doing something a little bit unprecedented at this point in Earthâs history." He added, "Thereâs nothing to say that complex biological life couldnât have emerged and thrived as far back as 2 billion years ago," but highlighted the need for more substantial evidence.
These findings, published in the scientific journal *Precambrian Research*, offer a tantalizing glimpse into the early evolution of life on Earth. While the debate continues, the research serves as a compelling reminder of the vast mysteries still awaiting discovery within our planet's ancient history.
