The rate, however, isn't slow enough for humans to take blood from an amber-encased mosquito and clone dinosaurs, like in Jurassic Park. "We believe this is the last nail in the coffin," of claims that scientists can get DNA from million-year-old fossils, says Morten Allentoft, a scientist from Copenhagen's Natural History Museum who worked on the project. Even in ideal preservation conditions, the scientists calculated that every single DNA bond would be broken at 6.8 million years: The youngest dino fossils are 65 million years old. And because scientists need long stretches of DNA to replicate it, they estimate that the oldest usable DNA will actually be one to two million years old. The record holder right now is DNA found in ice cores, at 500,000 years old.