The temples have distinctive architecture, typically a complex trefoil design, and were used from 4000 to 2500 BC. Animal bones and a knife found behind a removable altar stone suggest that temple rituals included animal sacrifice. Tentative information suggests that the sacrifices were made to the goddess of fertility, whose statue is now in the National Museum of Archaeology in Valletta. The culture apparently disappeared from the Maltese Islands around 2500 BC. Archaeologists speculate that the temple builders fell victim to famine or disease, but this is not certain.