Those who cling to the thought of cloning dinosaurs will have to be content with the “Jurassic Park” series (now with a fourth installment slated to premiere in June 2015). A new scientific study shows that obtaining the DNA to clone a dinosaur from amber-preserved insects is a technique destined to remain in the fiction section.
In “Jurassic Park,” the company that clones the terrifying T-rex and other denizens of Isla Nublar does so by extracting dino DNA-containing blood from mosquitoes preserved in amber. In the story, the mosquitoes were engulfed in tree resin just after snacking on a dinosaur, thus preserving them (and their meals) for millions of years. But the story hasn't just been limited to fiction; in the early 1990s, some scientists claimed to have successfully extracted DNA from amber-preserved insects up to 130 million years old.
Nowadays, most scientists think that the results are probably erroneous, the result of stray contamination. A new study from University of Manchester researcher David Penney and colleagues, published in the journal PLoS ONE, seems to firmly shut the book on those old discoveries. While using the latest sequencing technology in extremely clean environments, the team was not able to extract the DNA from even relatively young preserved insects.
“When we set about doing this, we weren’t trying to hammer a nail in the coffin of ‘Jurassic Park,’ as it were,” Penney said in a phone interview. “The reason we did it is because [previously,] researchers have managed to extract DNA from insects preserved in museum collections -- insects that had been on pins for up to 80 or 90 years.”
For their experiments, Penney and his colleagues examined two preserved stingless bees, one less than 60 years old, another around 10,600 years old, both hailing from Colombia. The insects were preserved in copal, which is hardened tree resin on its way to becoming amber. In the 60-year-old bee, the researchers managed to recover a tiny bit of DNA, but not from the bee itself; the biggest bit was a fragment of genetic material from a bacteria called Bradyrizobium japonicum. No ancient DNA was found in the 10,600-year-old bee.
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“We were therefore unable to obtain any convincing evidence for the preservation of ancient DNA in either of the two copal inclusions that we studied, and conclude that DNA is not preserved in this type of material,” the authors wrote. “Our results raise further doubts about claims of DNA extraction from fossil insects in amber, many millions of years older than copal.”
Scientists in the 1990s were using slightly different DNA sequencing techniques that would have amplified any modern contaminants that got into the mix. The sequencing methods the team used give equal treatment to all genetic material found in a sample; they’re much less likely to amplify any modern contaminants, according to Penney.
So, what sort of stray material might have fooled those previous researchers, anyway?
“Could be human skin cells, could be tuna cells off [their] tuna sandwiches,” Penney says.
SOURCE: Penney et al. “Absence of Ancient DNA in Sub-Fossil Insect Inclusions Preserved in ‘Anthropocene’ Colombian Copal.” PLoS ONE published online 11 September 2013.