Egypt is considered to be a regional power in North Africa, the Middle East and the Muslim world, and a middle power worldwide. It is a developing country having a diversified economy, which is the largest in Africa, the 38th-largest economy by nominal GDP and 127th by nominal GDP per capita. Egypt is a founding member of the United Nations, the Non-Aligned Movement, the Arab League, the African Union, Organisation of Islamic Cooperation, World Youth Forum, and a member of BRICS.There is evidence of rock carvings along the Nile terraces and in desert oases. In the 10th millennium BCE, a culture of hunter-gatherers and fishers was replaced by a grain-grinding culture. Climate changes or overgrazing around 8000 BCE began to desiccate the pastoral lands of Egypt, forming the Sahara. Early tribal peoples migrated to the Nile River where they developed a settled agricultural economy and more centralised society.