From Science Daily:
Science Daily (Sep. 10, 2009) — Analysis of a rock type found only in the world's oldest oceans has shed new light on how large animals first got a foothold on Earth.
A scientific team led by Professor Robert Frei at the University of Copenhagen in Denmark, and including scientists from Newcastle University, UK, and universities in Uruguay and Southern Denmark, have for the first time managed to plot the rise and fall of oxygen levels in the Earth's atmosphere over the last 3.8 billion years.
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