Chaco Canyon, a settlement of the ancient Anasazi culture in North America, had massive buildings. It must have been a major Anasazi center. Analysis of wood samples shows that some of the timber for the buildings came from the Chuska and San Mateo mountains, 50 miles from Chaco Canyon. Only a major cultural center would have the organizational power to import timber from 50 miles away.

In the argument given, the two portions in boldface play which of the following roles?