Oil study fills bacterial gaps in 'boring billion' years
For about a billion years of Earth’s history all life consisted of little more than a layer of slime, but then about 550 million years ago evolution burst back into action and provided it with the stunning array of species from which humans have evolved.
Some scientists refer to the period as the ‘boring billion’ as life seemed to take it easy and put some time into pondering its next move.
Now, a team of Tasmanian researchers have revealed ancient conditions that appear to have caused the long delay, and almost ended life on Earth.
The discovery was made using a new technique developed to hunt for mineral deposits.
According to University of Tasmania geologist Professor Ross Large and his international team, the quiet time was prompted by a lack of oxygen and nutrient elements, which placed evolution in a precarious position.
“During that billion years, oxygen levels declined and the oceans were losing the ingredients needed for life to develop into more complex organisms,” he said.
By analysing ancient seafloor rocks, Prof Large and his Australian, Russian, US and Canadian colleagues were able to show that the slowdown in evolution was tightly linked to low levels of oxygen and biologically-important elements in the oceans.
“We've looked at thousands of samples of the mineral pyrite in rocks that formed in the ancient oceans,” he said
“By measuring the levels of certain trace elements in the pyrite, using a technique developed in our labs, we've found that we can tell an accurate story about how much oxygen and nutrients were around billions of years ago.”
After an initial burst of oxygen, the study plots a long decline in oxygen levels during the ‘boring billion’ years before leaping up about 750-550 million years ago.
“We think this recovery of oxygen levels led to a significant increase in trace metals in the ocean and triggered the Cambrian explosion of life,” Professor Large explained.
“We will be doing much more with this technology, but it's already becoming clear that there have been many fluctuations in trace metal levels over the millennia and these may help us understand a host of events including the emergence of life, fish, plants and dinosaurs, mass extinctions, and the development of seafloor gold and other ore deposits,” he said.
The results of the research so far will be published in the March issue of the journal Earth and Planetary Science Letters.