Doubts radiometric dating
For a long time, geologists have used microscopic crystals called zircons as “time capsules” for dating rock strata.The tiny crystals are so durable it was believed they were virtually impermeable.“If you’re trying to look at archaeological sites at the order of 30,000 or 40,000 years ago, the ages may shift by only a few hundred years but that may be significant in putting them before or after changes in climate,” he says.Take the extinction of Neanderthals, which occurred in western Europe less than 30,000 years ago.
But if there was argon in the rock when it originally formed, then the age calculated will be millions of years too high. The greater the amount of daughter isotope, the greater the apparent age. Climate records from a Japanese lake are set to improve the accuracy of the dating technique, which could help to shed light on archaeological mysteries such as why Neanderthals became extinct.Carbon dating is used to work out the age of organic material — in effect, any living thing.Various geologic, atmospheric and solar processes can influence atmospheric carbon-14 levels.Since the 1960s, scientists have started accounting for the variations by calibrating the clock against the known ages of tree rings.