Is there something strange high up in the world’s tallest mountains If so, is it a big bear Is it a monkey Or is it a kind of man No one knows. This mystery has puzzled the world for years. In 1887, a mountain climber found large footprints in the snow. They looked like the footprints of a very large man. But men don’t walk without shoes in the snow! In 1906, another climber saw more than footprints. Far off, he saw a very large animal standing on two legs. As he watched, it ran very quickly. Fifteen years later, newspaper had new stories about the "something". A mountain climber said he had seen the "Snowman" walk slowly across the snow, far below him. He said it looked like a very large man. From then on, more and more people had stories to tell. But not until 1951 did a mountain climber bring back pictures of large footprints. "The pictures showed clearly that the Snowman walked on two legs." So it was not a bear or a monkey. Could it be an ape (类人猿) man The mystery grew! And the mystery keeps growing. Some day we may find out what it is that makes the large footprints. How long has the mystery of the Snowman puzzled the world since a mountain climber first found the large footprints in the snow By 2011, it is about ______ since a mountain climber first found the large footprints in the snow.