Australia is a country of contradictions. The oldest land on Earth, it was one of the last to be found by European sailors during the era of exploration. Aboriginals, the oldest continuously surviving culture in the world, became citizens of the country only 42 years ago. The sixth-largest country in the world by landmass, it has just more than half the population of the state of California. Despite its very low population density, Australia is often considered overpopulated, compared to the amount of water and fertile soil that is available for human use.