The key moment in the history of life on Earth – the tipping point at which there was enough oxygen in the atmosphere to support the evolution of complex animals and plants – occurred about 400 million years earlier than previously thought, a study has found.
Geologists studying rocks in Scotland believe that oxygen – the vital element for energy-hungry life forms – began to rise to useful concentrations in the Earth's atmosphere about 1.2 billion years ago rather than 800 million years ago, which was suggested by previous studies.
The discovery pushes back the point at which complex organisms could have begun to evolve from the simple microbes that had inhabited the planet for much of its history. But it raises the question: what was the ultimate spark that ignited the evolutionary explosion of life, leading to the immense diversity of species today?
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