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A recent study calls into question the validity of taking a strictly molecular approach to the sometimes murky science of species preservation, and it strongly suggests that scientists do not yet know enough about how certain genetic patterns detected in laboratory tests translate into the strengths and weaknesses of a wild animals.

Radio carbon dating information

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The clock was initially calibrated by dating objects of known age such as Egyptian mummies and bread from Pompeii; work that won Willard Libby the 1960 Nobel Prize in Chemistry.

But even he “realized that there probably would be variation”, says Christopher Bronk Ramsey, a geochronologist at the University of Oxford, UK, who led the latest work, published today in Science.

­The carbon-14 atoms that cosmic rays create combine with oxygen to form carbon dioxide, which plants absorb naturally and incorporate into plant fibers by photosynthesis.

Animals and people eat plants and take in carbon-14 as well.

Carbon-14 is radioactive, with a half-life of about 5,700 years.

Since the 1960s, scientists have started accounting for the variations by calibrating the clock against the known ages of tree rings.

By measuring the ratio of the radio isotope to non-radioactive carbon, the amount of carbon-14 decay can be worked out, thereby giving an age for the specimen in question.

But that assumes that the amount of carbon-14 in the atmosphere was constant — any variation would speed up or slow down the clock.

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.

ASTEROIDS: Scientists have discovered a very large asteroid impact site in Antarctica.

As little as 200 years ago mainstream English speaking scientist did not believe that stones fell from the sky contrary to all the anecdotal evidence over the past centuries.

Scientist for the last hundred years have been searching for a crator or remnants of space rock.

Finally in 2008 scientist think they have found an impact site at the bottom of a nearby lake Cheko.

The ratio of radiocarbon to stable carbon atoms in the atmosphere has varied in the past.

This is because the amount and strength of cosmic radiation entering the earth's atmosphere has varied over time.