In a crushing blow to Jurassic Park enthusiasts worldwide, the odds of successfully extracting genetic information from fossils preserved in amber appears to be downright nil. That's the verdict from a team of UK scientists who used highly sensitive sequencing techniques in an effort to detect ancient DNA molecules in fossilized insects.
"Because these fossils were captured in amber, there was a possibility that their DNA might resist degradation and be available to extract," says study leader David Penney, PhD, a biologist at the University of Manchester. "Unfortunately, we've shown that this is not the case."
"The blood may contain actual dinosaur DNA."
For decades, however, scientists suspected the opposite. In 1992, researchers out of the University of California, Berkeley, announced that they'd successfully extracted gene fragments from a 40-million-year-old bee that had been preserved in amber. "Sooner or later, we're going to find amber containing some biting insect that filled its stomach with blood from a dinosaur before getting trapped in the resin that eventually turned into amber," the study's leader, Dr. George Poinar, raved to The New York Times following the announcement. "The blood may contain actual dinosaur DNA. That will be an exciting discovery."
Subsequent research called those tantalizing results into question
That finding catalyzed a series of similar ones, including the purported extraction of DNA from ancient beetles, wood gnats, and termites, among other critters. Unfortunately, subsequent research called those tantalizing results into question: other groups of scientists couldn't replicate the findings, leading to a growing consensus that amber did not — as had initially been suspected — preserve fragile DNA segments over millions of years. And as DNA analysis techniques grew more sophisticated, it emerged that some earlier findings had actually isolated more contemporary DNA molecules — essentially sample contaminants — rather than ancient ones.
This new research offers compelling reinforcement of that skepticism. Earlier analyses of amber fossils relied on a technique called PCR amplification, which takes one small piece of DNA and then copies it thousands or millions of times. Unfortunately, Penney says, PCR tends to "selectively amplify more recent DNA that has not undergone as much degradation, which leads to false positives." So his team relied on a newer, more sensitive technique, one that "sequences everything within a sample, and so will pick up even the smallest strands of DNA."
"This would be the end of the road for these investigations."
They used that technique to extract DNA from insects that were trapped inside copal, which is resin that hasn't yet fully hardened into amber. The samples were relatively young (up to 10,600 years old), but the team was unable to detect any viable DNA — a finding which suggests that DNA extraction from even older, amber fossils would be extremely unlikely. "If we cannot pull DNA from copal, then we absolutely cannot do it from amber either," Penney says. "So this would be the end of the road for these investigations."