in the early 2000s; its economy is now based predominantly on services. It is a producer and net exporter of machines and electric energy through companies like Automobile Dacia and OMV Petrom. Romania has been a member of the United Nations since 1955, NATO since 2004 and the European Union (EU) since 2007. The majority of Romania's population are ethnic Romanian and religiously identify themselves as Eastern Orthodox Christians, speaking Romanian, a Romance language (more specifically Eastern Romance/Daco-Romance). The Romanian Orthodox Church is the largest religious denomination in the country. Etymology "Romania" derives from the local name for Romanian (), which in turn derives from Latin romanus, meaning "Roman" or "of Rome". This ethnonym for Romanians is first attested in the 16th century by Italian humanists travelling in Transylvania, Moldavia, and Wallachia. The oldest known surviving document written in Romanian, a 1521 letter known as the "Letter of Neacșu from Câmpulung", is notable for including the first documented occurrence of Romanian in a country name: Wallachia is mentioned as . Two spelling forms: and were used interchangeably until sociolinguistic developments in the late 17th century led to semantic differentiation of the two forms: came to mean "bondsman", while retained the original ethnolinguistic meaning. After the abolition of serfdom in 1746, the word rumân gradually fell out of use and the spelling stabilised to the form . Tudor Vladimirescu, a revolutionary leader of the early 19th century, used the term to refer exclusively to the principality of Wallachia. The use of the name Romania to refer to the common homeland of all Romanians—its modern-day meaning—was first documented in the early 19th century. In English, the name of the country was formerly spelt Rumania or Roumania. Romania became the predominant spelling around 1975. Romania is also the official English-language spelling used by the Romanian government. A handful of other languages (including Italian, Hungarian, Portuguese, and Norwegian) have also switched to "o" like English, but most languages continue to prefer forms with u, e.g. French , German and Swedish , Dutch (oe pronounced as Spanish u), Spanish (the archaic form is still in use in Spain), Polish , Russian (), and Japanese (). History Prehistory Human remains found in Peștera cu Oase ("Cave with Bones"), radiocarbon date from circa 40,000 years ago, and represent the oldest known Homo sapiens in Europe. Neolithic agriculture spread after the arrival of a mixed group of people