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Pre Historic Puzzles: Rocking the Cradle of Civilization For more than a century, archeologists were convincing that the cradle of civilization lay in Greece, Egypt, and Mesopotamia. The learning of the advanced peoples of this region, it was thought, gradually moved west into Europe. But in the last few decades these theories have been overturned, thanks to Nobel Prize-winning physicist Willard F. Libby and a substance knows as carbon 14. Carbon 14 is a radioactive substance that exists in minute quantities. In the late 1940's Libby discovered that all plants and animals absorb it. When they die, the carbon-like all radioactive substances-begins to decay at a regular rate. Libby was able to measure this rate and could thus use carbon 14 as an archeological calendar. Today it is known that half of the carbon 14 in living organism disappears in 5,730 years, half of what remains in an additional 5,730 years, and so on. How old is old? Many of the items found at prehistoric sites are made of organic material. By measuring the amount of carbon 14 remaining in the shaft of an old ax or a piece of pottery, for example, scientists can accurately determine its age. Radiocarbon dating has proved to be phenomenally accurate: it can date to within 100 years going back to 50,000 B.C. It is particularly useful on wood because it can be checked against Dendron-chronology, dating by tree rings. A new ring forms every year in the trunk of a tree as it grows: counting the number of rings enables one to determine the age of any tree. Where did civilization begin?