Claims of early sites present a challenge on two fronts. The first is technical: Dating a site convincingly can be difficult, depending on the context. Sediments can shift or be disturbed. What at first look like artifacts can turn out to be “geofacts,” created not by humans but by natural processes or animals. / As a result, many pre-Clovis sites “enjoy a Warhol-esque 15 minutes of fame, and then they disappear” because of real problems with the geology or the methods, said archaeologist James Adovasio.