1921–1933, 1947–1958 and 1962–1964. Malta became an independent Commonwealth realm known as the State of Malta in 1964, and it became a republic in 1974. Since 2004, the country has been a member state of the European Union. Geology Malta stands on an underwater ridge that extends from North Africa to Sicily. At some time in the distant past, Malta was submerged, as shown by marine fossils embedded in rock in the highest points of Malta. As the ridge was pushed up and the Strait of Gibraltar closed through tectonic activity, the sea level was lower, and Malta was on a bridge of dry land that extended between the two continents, surrounded by large lakes. Some caverns in Malta have revealed bones of elephants, hippopotamuses, and other large animals now found in Africa, while others have revealed animals native to Europe. Neolithic (5900 BC - 3850 BC) While until recently, it was believed that Malta's first inhabitants arrived in the islands in 5700 BC, it has now been established that this occurred around 5900 BC, as is evidenced by studies of ancient soils. These first Neolithic people have generally been assumed to have arrived from Sicily (about north), but DNA analysis shows that they originated from different parts of the Mediterranean, including both Europe and Africa. They were mainly farming and fishing communities, with some evidence of hunting activities. They apparently lived in caves and open dwellings. During the centuries that followed there is evidence of further contacts with other cultures, which left their influence on the local communities, evidenced by their pottery designs and colours. The farming methods degraded the soil; at the same time prolonged drought set in, and the islands became too dry to sustain agricultural practices. This occurred partly due to climate change and drought, and the islands were uninhabited for about a millennium. Research carried out as part of the FRAGSUS project, comprising analysis of soil cores from valleys, which contained ancient pollen and animal evidence from past environments, revealed that "climate change fluctuations made Malta uninhabitable in some periods of prehistory. There was a substantial break of around 1,000 years between the first settlers and the next group who settled permanently on the Maltese islands and eventually built the megalithic temples." Temple period (3850 BC - 2350 BC) A second wave of colonization arrived from Sicily in around 3850 BC. Prof. Caroline Malone has