Ancient 'Reef Stirs Debate Over Early Signs of Life in Australian Rocks

摘要

When paleontologists seek the roots of life, they head to rocks of the Archaean Eon, which range from 3.8 billion to 2.5 billion years old. But it's a tough task: The rocks are so battered and time-worn that any evidence of fossils is greeted with suspicion. For many years, an exception was a familiar-looking structure called a stromatolite, which has a modern analog formed by cyanobacteria. But when computer models suggested that simple chemical reactions and physical forces can mimic stromatolites, those fossils too were cast in doubt.