From Philip Metherell, Lindfield, West Sussex, UK
If Stone Age people did indeed use the flight of wild birds as a tool for navigation, could they also have taken their own birds? If these were unable to land on water, e.g. eagles or corvids, when released they would fly ever higher looking for distant land. If they saw land, they would fly towards it, but if there was no land, they would be forced to come back and land on the boat. What could be simpler? (31 January, p 32)
