Put Francisco Pizarro from your mind. Forget those tales of gold, Toledo steel and Spanish greed. It was nasty weather and more than 3,000 years of ecological damage that killed the Incas. The military daring of the conquistadores played only a minor part.
Scientists investigating plant growth changes in Peru have discovered that the Andes suffered devastating habitat disruptions that contributed to the Incas' defeat by a handful of Spanish soldiers.The project, by Alex Chepstow-Lacy of the University of Cambridge's plant sciences depart-ment, is the latest of several recent studies to show that eradication of habitats, extinction of species and pollution have followed Homo sapiens ever since we spread out of Africa 100,000 years ago.
The Cambridge project has studied pollen in soil at Marcacocha, a town close to Ollantaytambo, an Inca citadel, and ice cores from the Quelccaya glacier.
"Humans moved into South America more than 10,000 years ago," said Chepstow-Lacy. "By 4,000 years ago, farmers had completely stripped the trees from mountain sides and planted tubers, like potatoes, and cereals, like quinoa, from which people made bread."
Then, 2,000 years ago, the climate cooled and the crops failed, bringing widespread soil erosion, triggering an exodus from the Andes. Later, in about 1200 A.D., the climate improved and people returned. The resulting agrarian societies were unified into the Inca civilization, stretching from present-day Colombia to Bolivia.
But the underlying ecology was still fragile. Around 1500, the climate cooled again and the crops began failing - just as Pizarro arrived with his band of adventurers.
Weakened by seriously depleted food stocks, the Incas were in trouble even without the Spaniards. With them, their fate was sealed.
"It was a double whammy," said Chepstow-Lacy. "The Incas - for all their sophistication - never got over it. They were finally defeated at Ollantaytambo and disappeared from history. The Spanish then chopped down the trees they had begun replanting and that was that for the Andean ecology."
It's a grim but common picture. Studies of ancient nests made by rock hyraxes, a species of rodent, has shown that the ancient Jordanian city of Petra starved because people cut down its surrounding oak and pistacchio forests, creating an eroded, shrub-lined desert. Farming became impossible.
Another example is provided by the Clovis people, highly accomplished hunters descended from the first settlers who crossed the Bering land bridge that linked Russia to Alaska. Within a few hundred years of spreading across North America 12,000 years ago, they wiped out 75 species of large mammal, including mammoths and mastodons.
Similarly, around 50,000 years ago, Stone Age man arrived in Australia and promptly destroyed dozens of species, including giant kangaroos; the Diprotodon, a sort of browsing, rhinoceros-sized wombat, and a lion-like marsupial carnivore.
Later, as humans spread through the South Pacific, more than 2,000 species of birds were wiped out, and habitats set on fire and destroyed - long before European settlers reached those islands.
It's a frightening catalogue of extinctions carried out using only stone tools. Now that we have modern technology, the eradications have multiplied.
A United Nations global bio-diver-sity assessment shows that a total of 5,400 animals and 4,000 plant species, out of the small number so far scientifically examined, are threatened with extinction. Only 2 percent of the dry tropical forest of Central America now exists; the U.S. has lost 54 percent of its wetlands; and half of Thailand's mangroves have been destroyed.
"The adverse effects of human impacts on the Earth's biodiversity are increasing dramatically and are threatening the very foundations of sustainable development," according to Reuben Olembo, deputy executive director of the United Nations Environment Program.
In short, the story of the Incas is being repeated across the globe.