The Proto-Indo-Europeans (PIE) are the hypothetical prehistoric people of the Copper Age and early Bronze Age (or according to some modern theories, Neolithic or Paleolithic) who spoke the reconstructed Proto-Indo-European language, from which their existence from around 4000 BC is inferred. Their genetic phenotypes are unknown. Some things about their culture can be determined with confidence, based on the words reconstructed for their language: they used a kinship system based on relationship… (More on Proto-indo-europeans)