Culture is a powerful human tool for survival, but it is a fragile phenomenon. It is constantly changing and easily lost because it exists only in our minds. Our written languages, governments, buildings, and other man-made things are merely the products of culture. They are not culture in themselves. For this reason, archaeologists can not dig up culture directly in their excavations. The broken pots and other artifacts of ancient people that they uncover are only material remains that reflect cultural patterns--they are things that were made and used through cultural knowledge and skills.