In most cases, they wait for an amateur to get lucky, then make their move. Anthropologists can’t see what’s under the first layer of earth without digging—ground-penetrating radar isn’t sensitive enough to distinguish fossils from the surrounding rock—and there’s too much land and too few anthropologists to dig up every site where the geology favors bone preservation. So most anthropologists wait until a farmer, geologist, or curious child stumbles upon an interesting bone. Then they use geological maps, Google Earth, and good, old-fashioned walking around to determine the likelihood that there’s more to discover in the vicinity.
Caves are particularly promising areas for excavation. Early humans used them to hide from predators and the elements. Neanderthals, and possibly other early humans, may even have buried their dead in caves as early as 200,000 years ago. (Skeptics argue that early man simply liked to rest in hollows with a little snack and sometimes died in his comfy spot.) Some researchers, therefore, survey caves— particularly those in Siberia, where scientists are looking for evidence of the early humans of Eurasia and North America—without waiting for a fortuitous amateur find. They look for painted walls and artifacts like tools or bones lying on the ground. If they find nothing, they may dig a test hole about 1 meter square and a few inches deep. If that doesn’t turn anything up, they usually abandon the site.