A: Some prehistoric people in Texas dug holes to make homes archeologists call these pit houses. Sometimes artifacts are found where they were left on the floor of some of these houses, well below the surface of the ground. However, that is not usually the reason why archeologists have to dig to recover artifacts. Most of the prehistoric people living in central Texas were what we call hunter-gatherers. They moved around much of the time, using the animal and vegetation resources in an area for a few weeks, then moving on to their next campsite. Because they moved so much, they didn't go to the trouble to build permanent houses.
So why do archeologists have to dig? It's because dirt--what archeologists call sediment--has covered the campsites over time. There are many natural processes that cause sediment to be deposited. Rivers flood and deposit blankets of mud across the landscape. Wind blows sand, burying sites. Gravity can cause sediment to flow down hill rapidly in a landslide, or sites can be buried very slowly in a process called soil creep. All of these processes can lay down the sediment that archeologists dig through when they study a site.
Not all sites are buried this way. Prehistoric people lived in Texas more than twelve thousand years. Wherever they slept, cooked, made tools, butchered animals, or did anything that created trash, archeological sites were formed. Over the years, some of these sites were eroded and destroyed, some just lay at the surface, and some were buried. Archeologists dig because it is the buried sites that usually tell us the most about how prehistoric Texans lived.