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Further damning evidence comes from Tasmania, which retained its giant kangaroos (and various other megafauna) for four thousand more years, until falling sea levels allowed humans to finally invade—whereupon the island’s giant kangaroos (among six other large-bodied species) promptly died out.14 Any remaining doubters need only look to New Zealand. When Polynesian people first arrived by boat a mere 700 years ago, they found a unique island ecosystem where—thanks to millions of years of geographical isolation—birds rather than mammals or reptiles had evolved to become the dominant land animals. Giant flightless moas stalked the forests, while enormous eagles, the largest ever known, with wingspans on the order of 3 meters, soared above the mountains. Within as little as a century all—along with half of the islands’ other terrestrial vertebrates—were dead.15 This time there can be no dispute as to the cause of death or the identity of the killers, for Maori dwelling sites are surrounded by piles of moa bones—some so extensive that they have since been quarried for fertilizer. No doubt believing that the abundance of their moas would last forever (another pattern that keeps repeating itself), the Maoris wastefully ate only the upper legs and threw the rest away.16

Only one continent’s large animals survived relatively unscathed. That continent was Africa, whose megafaunal inhabitants had coevolved with hominids over millions of years and had therefore acquired a great deal of useful experience about living with Homo sapiens. As a result, Africa gives us the best idea of what a pre-human landscape might have looked like, with big animals like elephants browsing the undergrowth and herds of wild horses and cattle stirring up dust clouds across the savannah. Indeed, African ecosystems have been used as a model for proponents of “rewilding” parts of North America; if cheetahs, elephants, and camels can be imported into places like Montana, perhaps they could assume the ecological niches vacated by their extinct relatives, some have suggested.17 This is a romantic but vain hope, not least because the ancient homeland of these large surviving animals is seriously endangered by today’s generations of human beings. Africa is safe no more.

Right across the world, these lost big animals left “ghost habitats” behind—trees that still bear specialized fruits hoping some long-gone giant will distribute them, or thorny bushes protecting themselves against browsing by extinct large herbivores. In Brazil, more than 100 tree species still produce obsolete “megafauna fruit,” evolved for dispersal by extinct elephant-like creatures called gomphotheres. Not surprisingly, with no living animals to disperse their seeds, these trees are now themselves becoming endangered. In Madagascar many plants grow thin zigzag branches to protect themselves from leaf-munching elephant birds, another giant flightless bird that became a casualty of Homo sapiens—and that laid eggs so large it is thought to have inspired the legend of the roc in Sinbad the Sailor. Modern-day Siberia’s wet peaty tundra may stem from the loss of the mammoths, whose earlier grazing nourished a much more productive dry steppe-type biome before their extinction at human hands a mere 2,000 years ago.18 In Africa elephants play a key role in opening up forests by pushing over trees—a function their relatives in the Americas would also have served before being wiped out by man. In all cases, the vanished megafauna maintained a more diverse ecosystem than the simplified one that replaced them after their sudden demise.

All told, the Quaternary Megafaunal Extinction between 50,000 and 3,000 years ago carried off about half of the world’s large animals (including 178 species of large mammals). This was an extinction wave that bears comparison with the largest in the geological record—but it is still only a prelude to what was to come. The wipeout that accompanied human migration across