A study of DNA extracted from the leg bones of extinct moa birds in New Zealand found that the half-life of DNA is 521 years. So every 1,000 years, 75 per cent of the genetic information is lost. After 6.8 million years, every single base pair is gone. Bacterial RNA is much tougher and sequences have been recovered from ice crystals that are 419 million years old. These are only short fragments of 55 base pairs though.