DNA 'half life'

Reconstructing dinosaurs from ancient DNA has been dealt a blow with a new study finding genetic material can only last one million years.  An international team of researchers reached the finding after analysing DNA extracted from bones of the extinct New Zealand moa. They found that while short fragments of DNA could possibly survive up to one million years, sequences of 30 base pairs or more would only have a 'half-life' of around 158,000 years under certain conditions.