The World's highest and most spectacular mountains, the Himalayas of Nepal, India, and Bhutan, are built on the foundations of a much older mountain system, University of Arizona (UA) geoscientists have discovered. They have dated rocks that show Himalayas is predated by ancestral mountains that existed in the same area between 450 million and 500 million years ago. ''We conclude that the modern Himalaya mountains are built on the foundations of an ancient mountain range that may have been of similar dimensions,'' said UA geosciences Professor George Gehrels.