Life on Earth just (maybe) got older than everyone decided it was

Complex life on Earth may be older than previously thought. New findings suggest that conditions for life existed 1.5 billion years earlier than it was originally considered to have begun. While some scientists are compelled by the theory, others are not in agreement, claiming that optimal conditions alone do not equate to life being formed earlier. 

The history of rock

The general scientific consensus was that complex life started on Earth approximately 635 million years ago. However, a new theory suggests that animal life may have instead begun around 2.1 billion years ago. A study published in August 2024 in the journal Precambrian Research detailed how formations in rock samples, thought to be fossils, suggest that the conditions required for life appeared much earlier than previously decided. 

The fossil records, found in Gabon, indicate increased phosphorus and oxygen in the seawater, "which has previously been linked to accelerations in evolution," said Science Direct. "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," Ernest Chi Fru, one of the authors of the study, said in a statement. "Our study adds another, much earlier episode into the record, 2.1 billion years ago."

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An unusually large amount of macrofossils were found in the Franceville Basin of Gabon. Those macrofossils might indicate the first complex life on Earth. "These primordial lifeforms, slimy, single-cell organisms that would "wiggle" to move and reproduce with spores, were unearthed in a landlocked water body, indicating the primordial lifeforms never spread globally," said the New York Post. "Nevertheless, their proliferation 'set the stage' for the animal kingdom to evolve before they died out." Essentially, the "chemistry of the rock showed evidence that a "laboratory" for life was created just before the formation appeared," said the BBC. 

Conflicting views

If the theory is correct, "high levels of oxygen and phosphorus were made by two continental plates colliding underwater, creating volcanic activity," said the BBC. "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," said Chi Fru. The underwater volcanoes also "restricted and even cut off [the Franceville Basin] of water from the global ocean to create a nutrient-rich shallow marine inland sea." This could have occurred well before the Cambrian Explosion when most animal life began to form.  

Not everyone is in agreement with the findings of the study, though. "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," Graham Shields, a professor at University College London, said to the BBC. Others are interested in the findings but say more evidence is needed to make a true claim. "Oceanic carbon, nitrogen, iron and phosphorus cycles were all doing something a little bit unprecedented at this point in Earth's history," said Elias Rugen, a PhD student at the Natural History Museum, to the BBC. "There's nothing to say that complex biological life couldn't have emerged and thrived as far back as 2 billion years ago."