Ancient DNA (broadcast Friday, August 10th, 2007)

Antarctic dry valleys David Marchant / National Science Foundation

Researchers have been able to extract frozen bacteria from Antarctic ice samples ranging in age from 100,000 years up to eight million years old. Working in a lab, they were able to revive the bacteria -- with warmth and food, the bacterial colonies began to grow again. The younger bacteria grew much more healthily than the older samples did, however -- a finding that could cast a shadow on some theories of how life got its initial start on Planet Earth. The researchers found that in the Antarctic samples, every 1.1 million years the DNA was chopped in half. If bacteria were to have arrived on Earth riding on a comet or asteroid, the DNA of the organisms would likely have been too corrupted by damage from cosmic rays during their multi-million year voyage to be viable. An article describing the new findings is being published this week in the journal Proceedings of the National Academy of Sciences.