Tasmanian researchers found that lack of oxygen and nutrient elements caused evolution to come to a standstill for a time period
It is commonly believed that a sudden rise in oxygen levels led to the formation of complex life on Earth 550 million years ago. Prior to this, about 3.6 billion years ago, the first form of life evolved on earth in the form of a layer of slime. This led researchers to wonder why there wasn't any evolution during that one billion year gap. Now Tasmanian researchers may have found an answer to this mystery.
According to them, the lack of oxygen and nutrient elements caused evolution to come to a standstill during that one billion "boring years."
"During that billion years, oxygen levels declined and the oceans were losing the ingredients needed for life to develop into more complex organisms," University of Tasmania geologist, Professor Ross Large, said in a press statement.
For the study, Ross and his Australian, Russian, US and Canadian colleagues analyzed ancient seafloor rocks and found 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. And 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," he said. "We were initially looking at oxygen levels in the ancient oceans and atmosphere to understand how mineral deposits form, and where to look for them today. That's a focus of the Centre for Ore Deposit and Exploration Science (CODES), which we established with ARC and industry funding at UTAS in 1989," Ross explains. "But the technology we have developed to find minerals can also tell us much about the evolution of life."
Contrarily a recently conducted study found that complex life forms on Earth don't need high levels of oxygen to grow or survive. This raises question about the findings of the current study that lack of oxygen caused evolution to come to a standstill.
According to study author Daniel Mills, there may have been other ecological and evolutionary mechanisms at play.
"Maybe life remained microbial for so long because it took a while to develop the biological machinery required to construct an animal. Perhaps the ancient Earth lacked animals because complex, many-celled bodies are simply hard to evolve," he said in a statement.
Researchers of the new study speculate that the second rise in atmospheric oxygen levels led to a significant increase in trace metals in the ocean and triggered the 'Cambrian explosion of life'.
"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," said Ross.
The study was funded by the Australian Research Council and was done in collaboration with the Russian Academy of Science, University of California, the Yukon Geological Survey, Geological Survey of Western Australia, Flinders University, Museum Victoria, and Mineral Resources Tasmania.
Findings were published online in the March issue of the journal Earth and Planetary Science Letters.
