Scientists have failed to find any trace of DNA in insects trapped in amber some 30 million years ago. The findings, reported in the 22 April Proceedings of the Royal Society, Biological Sciences, may sound a death knell for efforts to salvage a snip of ancient DNA to help unravel evolutionary relationships between living species and their ancestors.
In the past few years, several groups of scientists have claimed to have extracted genetic material from insects preserved in amber, or from fossilized tree resin. None of these results has been independently replicated, though, and critics have long suspected that the "ancient" DNA was actually contaminants from people handling the amber or other modern DNA sources.
Now a new research project has produced what many regard as a definitively negative result. Evolutionary biologist Jeremy Austin and his colleagues at the Natural History Museum in London bent over backward to avoid contamination. That included getting a spanking-new lab, with never-before-used instruments, at a cost of $240,000. For their analyses, the researchers used samples from the same amber collections that provided a termite and a bee from which scientists claimed in 1992 to have isolated DNA. But after 2 years, Austin's group reports having found nary a wisp of DNA.
That casts serious doubts on the original reports, as well as a 1993 claim by scientists at California State Polytechnic University who said they had extracted DNA from a 125 million year old Jurassic Park-age weevil. Many scientists doubted these claims because cells and their DNA generally start degrading within hours of death. Only in dry and frozen places such as the Tyrolean Alps, where the 5000-year-old "Ice Man" was found, have body tissues and DNA been successfully preserved.
Molecular biologist Svante Pääbo of the University of Munich, one of the scientists who isolated the Ice Man's DNA, says that he is "not surprised at these negative results from amber." But Austin says he and his colleagues had expected to be able to replicate the earlier results. "We had high hopes at the beginning," he says, "so these negative results are disappointing."