By midnight the coffee had stopped working on Sam, but he’d learned enough to keep him awake. The Eemian was the last period of interglacial warming before our current warmer era, the Holocene. Something strange had occurred in the Eemian. 100,000 years ago, in the middle Pleistocene, within only a few hundred years, the levels of greenhouse gases had mysteriously gone off the charts and Earth had warmed a few degrees Celsius—enough to melt the ice covering most of Greenland and much of Antarctica. During this period of unexplained warming—sometimes called the Marine Isotope Stage 11, sometimes the Yarmouth Event—sea levels rose more than 50 feet, to cover much more of the Earth’s surface than they do today. It took thousands of years for the planet to cool down enough to once more cover the poles in ice and the sea levels to fall, and then, for the next 80,000 years, glaciers covered most of North America and Europe. But 20,000 years ago Earth began warming again, and after a further thaw some 12,000 years ago, humans began to develop agriculture and build cities: civilization.
But what had happened to the human population during the Eemian warming? How had our ancestors dealt with such relatively rapid change? Sam knew just whom to ask: his Anthropogeny professor, Harry Bickford. But that would have to wait. Tomorrow was his father’s welcoming party, and he’d promised to attend.