For three San trackers, their quarry wasn't the usual animals that roam the Kalahari desert. Their prey were a long - dead people whose tracks could still be followed in some of Europe's deepest caves.The trackers were invited by two German academics to interpret Stone Age footprints that have been left in the mud and clay of caves. For years, researchers have tried to work out what our ancestors were up to in these caves.European researchers had thought a set of tracks were left from a dance, but the trackers had a more mundane explanation and have provided an insight into what they were doing there.