MADRID — In Vilcabamba, a small town in southern Ecuador, people live to be more than 100 years old. In Quechua, the town’s name Huillopamba means Sacred Valley, but for the rest of the world, it is known as the Valley of Longevity or “the land of the oldest old people in the world.” More than a decade ago, this peculiarity attracted too many tourists which damaged the inhabitants’ source of livelihood: The Vilcabamba River was modified to widen the road leading to the town. Altering the river’s natural course caused flooding. The way of life and even the average age of the people in the valle…