ABSTRACT
Gazing down over the world from above in the Middle Ages, in AD 1300 perhaps, one of the heavenly creatures which people thought existed – an angel or a dragon or the swift eagle Garuda – might have discerned changes since ancient times; swathes of forest removed; new machines being used, plowing taking place faster over longer stretches of fi eld, trade reviving and extending further. The huge seas bore little traffi c as yet, but there were daring Polynesian voyagers, Chinese junks, and Inca rafts in the Pacifi c, European and Arab traders on the Mediterranean Sea and Indian Ocean, Vikings venturing in the Atlantic to Iceland, Greenland, and far western Vinland, and Maya canoes in the Caribbean and Gulf of Mexico. These were widely separated pioneers on nearly empty waters. But the sky visitor would have observed more people on Earth. Built-up areas were spreading and, with them, clearance, erosion, and advancing desert. The Earth as a whole was, however, full of life in many thriving ecosystems. Parts of the continents were still covered with forests. Those places might have looked wild, but peoples had lived there for centuries or millennia, and had learned to subsist within their local ecosystems. Elsewhere, the rate at which humans were altering the face of the Earth was slow but accelerating. It was not increasing at a steady pace, but it was faster than it had ever been. Certain societies were learning skills that would in future times become more effective. They were learning to learn about the world – haltingly, with insuffi cient methods – but learning nonetheless. In the age to come, they would break forth upon the rest of the Earth. Preparations for rapid modern changes were made in the Middle Ages.
