In 1905, Harvard University students George Will and Herbert Spinden made the first scholarly archaeological study of a Mandan earthlodge village site. At Double Ditch, they excavated portions of six midden mounds, two houses, six cache pits, and the two fortification systems visible on the surface. Study of the artifacts and other material remains found in these features allows archaeologists to date the span of village occupation and identify changes in Mandan diet, health, and lifeways. Some midden mounds consisted mostly of earth, while others contained many broken animal bones, corn, beans, layers of charcoal and ash, pottery, stone tools, and other items. The oldest items are generally found at the bottom of the midden mounds, and careful scientific excavation can show how Mandan artifacts and lifeways, including tools and diet, changed over time.