In a paper that was published in the September 26, 2013 issue of Nature, Dr. Crowe and his colleagues report geological evidence that there were low concentrations of oxygen in the Earth's atmosphere at least 3 billion years ago, 700 million years earlier than was previously thought. This raises new questions about the evolution of early life and how it led to the eventual oxygenation of the Earth's atmosphere. According to Dr. Crowe, "This study now suggests that the process began very early in Earth's history, supporting a much greater antiquity for oxygen producing photosynthesis and aerobic life". These exciting findings have been reported on by the CBC, the BBC, NBC news, Canadian Press, and the International Business Times.
To learn more about Dr. Crowe's findings, see the articles about his findings on:
Faculty of Science (http://science.ubc.ca/news/728)
International Business Times http://www.ibtimes.com/oxygen-appeared-earth-700-million-years-earlier-previously-thought-study-1410906