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First Life

October 20, 2015

Life on earth may have emerged even earlier than previously thought.



Signs of life from the dawn of our planet. I’m Bob Hirshon and this is Science


Earth is 4.5 billion years old, and rocks 3.8 billion years old contain traces of microorganisms. Now, UCLA geochemist Elizabeth Bell reports in the Proceedings of the National Academy of Sciences on signs of life going back even further: carbon isotopes linked to living cells preserved in zircon crystals four point one billion years old.


Many of our earlier ideas about the early earth, which it was traditionally seen as sort of a dry, hellish landscape, bombarded constantly by meteorites, and these zircons are telling us a very different story.


The zircons formed under cooler conditions than were thought to exist on Earth that far back, and possibly in the presence of water. If so, they could not only change our understanding of the evolution of life, but of the planet itself. I’m Bob Hirshon, for AAAS, the science society.