The petroglyphs were carved on a granite rock face that was once part of an island, meaning people would have had to make the carvings while standing on a boat, or from a platform constructed on ice, said Martin Ostholm, a project manager with the Foundation for Documentation of Bohuslan's Rock Carvings who is one of the archaeologists who discovered the petroglyphs, told Live Science.Bohuslan is already known for its rock carvings, including Bronze Age art made at Tanum... The team was looking for new petroglyphs in the area when they came across the moss-covered rock face. They noticed some...