In recent months, researchers have unraveled the secret of a 500-year-old creature’s eternal youth, discovered the more or less exact age of the “common ancestor” of all living things, and even found out how the Egyptians built their first pyramid. To this collection of extraordinary events, we have to add another milestone. Researchers seem to have stumbled upon the oldest “complex life form,” rewriting what we thought was the “origin of life on Earth.”
The discovery. Until now, the consensus was that the first animals appeared around 635 million years ago. Now, an international team of researchers say that rock samples indicate an increase in phosphorus and oxygen in seawater, which other studies have previously linked to an acceleration in evolution.
A new analysis of marine sedimentary rocks in the Franceville Basin in Gabon, located off the west coast of Africa, has revealed that they date back about 2.1 billion years.
The mold that would change everything. If the study is accurate, researchers would have evidence to support their theory that complex life on Earth began 1.5 billion years earlier than previously thought. Researchers must now confirm that these are indeed ancient fossils.
Professor Ernest Chi Fru of Cardiff University led the research, which involves an international team of scientists. As Chi Fru told the BBC, if his theory is correct, these life forms would have been like slime mold, a brainless single-celled organism reproduced by spores.
Macrofossils found in the Franceville basin.
According to the researcher, “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.”
Franceville, a special place. The research team went to the site with many clues. Many fossils, large enough to be seen without a microscope, had been discovered in the basin. Previous studies have also suggested that these macrofossils could be the first complex life forms on the planet.
In the paper, the team links the water’s nutrient enrichment to the collision of two ancient continents, which created a shallow inland sea and conditions for cyanobacterial photosynthesis. This chemical process would have led to an underwater environment more conducive to biological complexity.
A natural laboratory. Following this hypothesis, the researchers say that such an environment would eventually create a kind of natural laboratory for organismal diversity and evolutionary leaps in size and structure. However, because the body of water remained isolated, these more sophisticated life forms wouldn’t have been able to spread elsewhere or survive the next leap forward.
For Chi Fru, the undersea volcanoes were key at this point because “they 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.”
Life in two parts. The work suggests that complex life on Earth evolved in two stages: one after the first significant increase in atmospheric oxygen 2.1 billion years ago and another after a second increase 1.5 billion years later.
“These observations make it possible that the appearance of macrofossils at Franceville may mark a unique window into our understanding of the conditions that enabled and constrained the evolution and disappearance of the first macrobiological life forms on Earth,” the researchers conclude.
This article was written by Miguel Jorge and originally published in Spanish on Xataka.
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