“ I don’t know what gods they prayed to, but this is a dream find.” For decades, many archaeologists have maintained that humans spread across North and South America only at the end of the last ice age.... Potter also questioned some of the dates scientists have assigned to their finds.... If a tool sinks into underlying sediment, for example, it may appear to be older than it really is. The footprints were first discovered in 2009 by David Bustos, the park’s resource program manager....