10 October 2012
Reconstructing dinosaurs from ancient DNA has been dealt a blow with a new study finding genetic material can only last 1 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 1 million years, sequences of 30 base pairs or more would only have a half-life of around 158,000 years under certain conditions.
Lead author Dr Morten Allentoft from Murdoch University's Ancient DNA lab in Perth says their results contradict earlier studies which claimed to have extracted DNA fragments several hundred base pairs long from dinosaur bones and preserved insects, claims which underpinned the storyline of the 1993 movie Jurassic Park.
"What we show here with the decay rate of DNA is that this is never going to be possible," Dr Allentoft said.
"It may be that you can have extremely short fragments of DNA, only a few base pairs that persist for maybe a million years, maybe even longer."
Dr Allentoft says the earlier findings may have been due to contamination with human DNA.
Rate of decay
The latest study, published in the Proceedings of the Royal Society B, also establishes a DNA decay rate which could help identify specimens likely to yield useful genetic material.
It might also one day enable DNA to be used to date bones and teeth or even be used for forensic investigation of human remains.
Dr Allentoft says the idea was first hinted at in 1970s, but subsequent studies have failed to pin it down.
"One of the reasons is because there is so much environmental noise, different temperatures, different soil conditions in different places," he said.
The researchers overcame this hurdle by using "a lot of material from the same small area".
The moa bones were excavated from three adjacent sites within a five-kilometre radius in North Canterbury, New Zealand.
According to Dr Allentoft, the next step is to explore how environmental factors affect the rate of decay, which he hopes will lead to a more accurate and more comprehensive model of DNA decay.
