Most experts believe that complex life on Earth can be traced back to the Cambrian period about 635 to 800 million years ago, but some researchers say they now have evidence that dramatically rewrites the evolutionary story. According to an international group led by Ernest Chi Fru of Cardiff University, the very first (but ultimately unsuccessful) simple single-celled organisms arrived on Earth 2.1 billion years ago, more than 1.5 billion years earlier than current prevailing theory. However, it is no surprise that skeptics are already heeding such an important claim.
Evidence of the first microbial life on our planet dates back to 3.7 billion years ago, but it took at least another 1.3 billion years for oxygen-based cyanobacteria to arrive. Current fossil records show that some of the earliest forms of animal life, such as sea sponges, emerged about 800 million years ago. Meanwhile, researchers understand that the increase in phosphorus and oxygen levels in seawater in the Cambrian period, 635 million years ago, stimulated the evolutionary track that leads to today’s biodiversity. But the Chi Fru team now claims that at least one other attempt at life occurred in the distant past. The theory, presented in a study published July 25 in the journal Precambrian researchpoints to alleged fossils and rock formations in present-day Gabon as evidence.
“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-celled organisms to complex organisms such as animals and plants,” says Chi Fru. said an accompanying statement on July 29.
According to Chi Fru, these necessary phosphorus and oxygen levels came from rare underwater volcanic activity that followed the collision and bonding of the Congo and São Francisco. cratons into a single body. A subsequently created shallow inland sea then formed a nutrient-rich testing environment for the first experiments in complex biological evolution.
“This created a localized environment where cyanobacterial photosynthesis was abundant for extended periods of time, leading to the oxygenation of local seawater and generating a large food source,” Chi Fru argued. “This would have provided sufficient energy to promote an increase 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.”
[Related: All living birds share an ‘iridescent’ ancestor.]
But don’t expect complexity from the two-billion-year-old deep-sea evolutionary experiments. According to the team, these life forms resembled slimy, single-celled fungal cultures that reproduced using spores. And while these mindless organisms were reportedly capable of small movements, the isolation of the inland water body and the resulting nutrient deficiency eventually caused the proto-slime to eventually become extinct.
Such a bold claim is not without skeptics. Like the BBC As noted on July 28, many experts believe that the so-called “fossils” cited by Chi Fru’s team are not actually fossils at all, but simply masses of (albeit still unexplained) geological formations. Others, meanwhile, are not opposed to the possibility that instances of higher nutrient levels occurred as early as 2.1 billion years ago, but are still not convinced that this was sufficient for complex life to begin.
Either way, critics say it will take a lot more evidence before they push back their evolutionary timeline by 1.5 billion years.