sentences:  The internal timbers often feature bas-relief carvings of ancestors, jewelry, animals, fish and boats with a balance of male and female elements that is essential for Niassan concepts of cosmic harmony.The more opulent houses are further decorated with freestanding wooden carvings and the internally exposed rafters are adorned with jaw bones from pigs that were sacrificed for the workers' feast at the time of the houses' completion.The December 2004 Indian Ocean earthquake and tsunami caused (only) coastal damage to Nias, but the March 2005 Nias earthquake had a devastating effect on the island.