A rapid rise in oxygen levels ignited a burst of evolutionary innovation that spawned complex multi-cellular animals more than 550 million years ago, new evidence suggests.
At Mistaken Point in Newfoundland, Canada, the oldest fossils of the enigmatic flat, soft-bodied Ediacara-period fauna spread across the sea floor within five million years after oxygen permeated the waters.
The chain of events started with a glaciation that covered much of the planet with thick ice sheets until 580 million years ago. 鈥淎t the end of the Gaskiers glaciation, it鈥檚 like you flicked a switch,鈥� says Guy Narbonne of Queen鈥檚 University in Kingston, Ontario, Canada.
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The rocks change colour within a few metres diplaying differences in mineral concentrations, such as iron. The iron compounds reveal a rapid rise in oxygen to at least 15% of today鈥檚 level, he says.
Complex communities
Narbonne believes the big thaw triggered a boom of phytoplankton that pumped oxygen into the air, which quickly permeated the sea.
Microbes had dominated the planet for billions of years, but oxygen changed the rules and put evolution on fast-forward. The first Ediacara fossils date from 575 million years ago, and 10 million years later complex communities of filter-feeders had spread over the sea floor.
鈥淲e see animals [from the Ediacara period] that are over 2 metres long in Newfoundland,鈥� Narbonne told 快猫短视频.
Animals evolved mobility by 555 million years ago, and the Cambrian explosion of evolutionary diversity began 542 million years ago.
Journal reference: Science (DOI: 10.1126/science/1135013)
