The Sherpa migrated from eastern Tibet to Nepal hundreds of years ago. Prior to Western intrusion in the twentieth century, the Sherpa didn't climb mountains, they reverently passed by the high peaks of the Himalaya, believing them to be the homes of the gods. The Sherpa eked their livelihood from high-altitude farming, cattle raising, and wool spinning and weaving.
It wasn't until the 1920s that Sherpa became involved in climbing. The British, who controlled the Indian subcontinent at the time, planned mountain climbing expeditions and hired Sherpa as porters. From that point on, due to their willingness to work and ability to climb the world's tallest peaks, mountaineering became part of the Sherpa culture.
Though numerous expeditions made the attempt, it wasn't until 1953 that Edmund Hillary and a Sherpa named Tenzing Norgay managed to reach the 29,028 foot (8,848 meter) peak of Mount Everest. After 1953, countless teams of climbers invaded the Sherpa homeland, making western snacks more common than traditional Sherpa food. In 1976, the Sherpa homeland and Mount Everest became protected as part of Sagarmatha National Park. The park was created through the efforts not only of the government of Nepal, but also through the work of the Himalayan Trust, a foundation established by Hillary.
With the transformation of the Sherpa culture and way of life has also come increased income. Sherpa who work as guides, cooks, and base camp staff have an income far exceeding that of the average Nepalese. For the most part, Sherpa no longer serve as porters - they contract that job out to other ethnicities but retain positions such as head porter.
Through the Sherpa have experienced westernization, their income from climbers has helped them to preserve their society. They've managed to keep alive most of the important parts of their culture.