With his hunt for ancient DNA, Eske Willerslev was a maverick for years. Nobody believed it was possible, but Willerslev stubbornly kept believing in his plan. After many years of failure, Willerslev finally found what no one expected: the genetic traces of a lush forest from before the ice age, more than two million years ago. An entire ecosystem with several species could be identified from their DNA. It heralded a new era in which scientists use DNA to travel back millions of years and piece together vanished ecosystems.