The Cambrian explosion of life was one of the biggest moments in Earth's lifetime, around 540 million years ago, when complex, multi-cellular life burst out all over the planet.
While scientists can pinpoint this pivotal period as leading to life as we know it today, it is not completely understood what caused the Cambrian explosion of life.
Now, researchers led by Arizona State University geologist L. Paul Knauth believe they have found the trigger for the Cambrian explosion.
It was a massive greening of the planet by non-vascular plants, or primitive ground huggers, as Knauth calls them.
This period, roughly 700 million years ago virtually set the table for the later explosion of life through the development of early soil that sequestered carbon, led to the build up of oxygen and allowed higher life forms to evolve.
Knauth and co-author Martin Kennedy, of the University of California, Riverside, have presented an alternative view of published data on thousands of analyses of carbon isotopes found in limestone that formed in the Neoproterozoic period, the time interval just prior to the Cambrian explosion.
"An explosive and previously unrecognized greening of the Earth occurred toward the end of the Precambrian and was an important trigger for the Cambrian explosion of life," said Knauth.
"During this period, Earth became extensively occupied by photosynthesizing organisms," he added.
"The greening was a key element in transforming the Precambrian world - which featured low oxygen levels and simple, bacteria dominant life forms - into the kind of world we have today with abundant oxygen and higher forms of plant and animal life," he explained.
By carefully plotting carbon isotopic data against oxygen isotopic data, a process Knauth said took three years, the researchers began to formulate a very different type of scenario for what led to complex life on Earth.
Rather than a world subject to periods of life-altering catastrophes, they began to see a world that first greened up with primitive plants.
"The greening of Earth made soils which sequestered carbon and allowed oxygen to rise and get dissolved into sea water," Knauth explained.
"Early animals would have loved breathing it as they expanded throughout the ocean of this new world," he added. (ANI)