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Scientists following two different lines of evidence have just published research that may help resolve "Darwin's dilemma," a mystery that plagued the father of evolution until his death more than a century ago.Biologists and geologists have been puzzled for decades over why life began so early on this planet, and then took so long to get interesting.Some estimates indicate the earth was only a few tens of millions of years old when the first simple organisms appeared. There was a little evolution over the first billion years when single-celled organisms morphed into bacteria, slimy algae and other simple kinfolk, but it was still pretty dull.It didn't get much better until nearly 600 million years ago when the most dramatic period in the biological history of the planet erupted in what has become known as the "Cambrian Explosion."
* * * A paper published last week in Science by Noah Planavsky of Yale University and Christopher Reinhard of Georgia Institute of Technology, based on ancient sediments from China, Australia, Canada and the United States, suggests that scientists have long overestimated the amount of oxygen in the earth's atmosphere in the pre-Cambrian era just before the "explosion."Many had thought the air was about 40 percent oxygen (around twice what it is today) but oxidized chromium -- which is directly linked to oxygen in the atmosphere -- in those sediments indicates the percentage was only about one-10th of one percent.No complex organism known today could survive in a world with that little oxygen, so if this team is correct, the stage was not yet set for rapid evolutionary processes. Something had to change before the explosion could occur. * * *
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Topic: 'Darwin's Dilemma' May Be Solved (Read 772 times)
