In a book written about traditional Greece, the author (Greek) vehemently asserts that the Greek people are of a 'purely Mediterranean temperament', despite their inevitable subjection to 'Eastern influences' due to the long Ottoman occupation. This is the kind of statement that one would expect from very nationalistic Greeks, who believe in some kind of racial 'purity', and who like to forget many indisputable facts, which challenge any notion of racial purity, among them, the fact that there was no nation of Greece until 1830, following the Greek War of Independence, and that the fledging Greek nation at first included only the Peloponnese, Central Greece, and the Cyclades and Sporades island groups. The Ionian islands re-joined the nation in 1864 (ceded to it by the British). Thessaly and part of Ipiros were not added until 1881, and, added only by 1913, after the Second Balkan War, were southern Macedonia (the largest nomos/prefecture in modern Greece), part of Thrace, Crete, another piece of Ipiros, and the northeast Aegean islands. The Dodecanese islands only re-joined Greece in 1948.
Before the centuries of Ottoman occupation (roughly from around the mid15th century until the end of World War I), the regions that make up modern Greece were part of the Byzantine Empire (4th to 15th centuries), which constituted the eastern sector of the Roman Empire. Though united by Greek language, and by Greek Orthodox Christianity, not only Greeks inhabited the territories now belonging to modern Greece; nor were Greeks the only peoples who inhabited those territories during Ottoman times.
There were Vlachs (a semi nomadic shepherd people who speak a Latin based tongue), Sarakatsani, (nomadic shepherds who speak a very ancient Greek dialect), Jewish communities widespread in Hellenistic times both on what is now mainland Greece and on present day Greek islands. There were also gypsies, Slavs, Turks, Arabs, and other peoples. All of them (at least one would think) had to have had some influence on the Greeks with whom they shared common territory.