WELSH scientists believe we are a lot older than we thought - and life on earth may have began 1.5 billion years earlier than believed.
A team of scientists have uncovered evidence which may shatter the broadly accepted opinions that first sign of animal life emerged on earth 635 million years ago.
But a team have discovered new evidence that an ecosystem for animal life existed 2.1 billion years ago.
The scientists led by Cardiff university experts found evidence of the much earlier environmental conditions in the Franceville Basin near Gabon on the Atlantic coast of Central Africa.
Their research adds to the dispute over whether unexplained formations found there are actually fossils or not.
The scientists looked at the rock around the formations to see if they had evidence of containing nutrients - like oxygen - that could have supported life.
If their theory is correct, the life forms would have been like slime mould - a brainless single-cell organism that reproduces with spores.
The team said the organisms were restricted to an inland sea, did not spread and eventually died out.
Dr Ernest Chi Fru, the paper’s lead author, worked with an international team of scientists.
The Reader at Cardiff University’s School of Earth and Environmental Sciences said: “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.
“We already know that increases in marine phosphorus and seawater oxygen concentrations are linked to an episode of biological evolution around 635 million years ago.
“Our study adds another, much earlier episode into the record, 2.1 billion years ago.”
But other academics - not involved in the research - have some reservations on the findings and said more evidence was needed.
Professor Graham Shields at University College London said: "I'm not against the idea that there were higher nutrients 2.1 billion years ago but I'm not convinced that this could lead to diversification to form complex life."
However, Dr Chi Fru said his work helped prove ideas about 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," 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."
Dr Chi Fru added: “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.
“This created a localised environment where cyanobacterial photosynthesis was abundant for an extended period of time, leading to the oxygenation of local seawater and the generation of a large food resource.
“This would have provided sufficient energy to promote 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.”
Their paper published in the scientific journal Precambrian Research.
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