An international team of scientists has uncovered environmental evidence of the earliest experiments in the evolution of complex life on Earth.
This finding, led by researchers from Cardiff University, challenges the widely accepted timeline that animals first emerged around 635 million years ago.
The team discovered evidence of a much earlier ecosystem in the Franceville Basin near Gabon on the Atlantic coast of Central Africa, dating back over 1.5 billion years earlier than previously thought.
Their study, published in Precambrian Research, describes a unique episode of underwater volcanic activity following the collision of two continents, creating a nutrient-rich environment conducive to early biological evolution.
Dr. Ernest Chi Fru, the lead author and a Reader at Cardiff University’s School of Earth and Environmental Sciences, highlighted the significance of phosphorus availability in the environment as a key component in the evolution of life.
"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," Dr. Chi Fru explained.
The Cardiff-led team identified a link between environmental change and nutrient enrichment, which may have triggered the evolution of large-sized fossils of macroorganisms from this period. These fossils, the earliest of their kind in the geologic record, have been a subject of debate among scientists.
Geochemical analysis of marine sedimentary rocks deposited 2.1 billion years ago provided new insights into these large fossils. Dr. Chi Fru elaborated, "We think that the underwater volcanoes, which followed the collision and suturing of the Congo and S£o 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 isolated environment allowed cyanobacterial photosynthesis to thrive, leading to the oxygenation of local seawater and the generation of a substantial food resource. This, in turn, provided sufficient energy to promote an increase in body size and more complex behavior in primitive animal-like life forms.
However, the restricted nature of this water mass and the hostile conditions beyond it likely prevented these early life forms from spreading globally.
The study suggests a two-step evolution of complex life on Earth: the first major rise in atmospheric oxygen content 2.1 billion years ago, followed by a second rise 1.5 billion years later.
This discovery not only pushes back the timeline for the emergence of complex life but also provides crucial insights into the environmental conditions that facilitated this significant evolutionary leap.
