Lost worlds found

Abstract

Sugar cubes of buried soil reveal how ecosystems warmed after the last ice age.For decades, scientists have debated why the so-called megafauna disappeared from the Arctic and much of the rest of the world. Now, ancient DNA data have entered the fray. By sequencing whatever DNA emerges (called eDNA) from even a thimbleful of ancient soil, researchers are reconstructing ancient ecosystems as far back as 700,000 years ago with astonishing clarity. In 2011, they documented that a decline in the big herbivores' favorite foods as the ice age thawed coincided with the animals' disappearance. And a paper this week shows that local extinctions were also tied to bursts of warming. Other eDNA data—in this case from lake sediments—are illuminating how the postglacial thaw transformed other landscapes too, such as temperate forests. Finally, eDNA from Antarctic ice cores promises to reveal what happened in the Southern Hemisphere many thousands of years ago.