This is eerily well timed with the Jurassic Park rerelease. Scientists are making progress in bringing extinct animals back to life through cloning—and have actually brought one back, the Pyrenean ibex, although it lived only for a few minutes. At a conference in Washington last week, scientists from Australia reported they had attempted to bring back a frog, but they were able only to make early embryos—and even those died. As fun as it sounds to walk with woolly mammoths, other scientists have warned that it could be dangerous to return to the past, such as when there were 3 to 5 billion passenger pigeons. And there likely won’t be any dinosaurs—they haven't left behind any DNA.