Answer:
Beginning with the top-most layer (most recent) is necessary so as not to disturb or destroy fragile remains and the only real method. One couldn't start at the bottom and work their way up!
Explanation:
In stratigraphic excavations, deposits from a site are removed in reverse order to determine when they were made. Each deposit is assigned a number, and this number is appended to all objects, including artifacts, bones, and soil samples containing organic matter, found in the layer.
