While there's not much historical record of when the first zip line came along, there is ample evidence that people living in mountainous regions -- particularly the Himalayas and the Alps -- strung up zip lines quite early in their culture to both traverse dangerous country and to receive and carry supplies more efficiently.
Of course, mountain climbers have also been partial to the zip line for some time. While a Tyrolean traverse is a common mountaineering practice (shimmying across a line to cross between two steep points, sometimes without a pulley at all), the zip line one-upped the Tyrolean by using the gravity of the slope to make the process a little quicker.
On a more contemporary note, it might surprise you to know that the people who popularized zip lining were those reckless thrill seekers known as wildlife biologists. Indeed, it was biologists studying densely forested areas that needed a way to unobtrusively snake into -- or above -- a forest canopy.
It was this unlikely reason that zip-line tours -- also referred to as canopy tours -- sprung up as a recreational activity in the rainforest of Costa Rica under the banner of eco-friendly tourism. Promising the adventure of flying like a bird through a natural habitat, these zip-line rides have become a huge industry in the adventure tourism trade of that region.
Zip lines have also become a large part of ropes challenge courses, designed to teach teamwork and provide recreational activities through team-building and problem solving, as there are generally high-fives all around when a high-speed trip down a cable on a frighteningly simple machine ends in all participants still breathing.
Spreading in popularity, zip lines have sprung up throughout the United States and internationally. In fact, according to the Association of Challenge Course Technology, there are more than 150 courses in the United States alone [source: Allen]. Later, we'll check out some of the most extreme and intriguing zip lines in the world. But before we do ... safety first.