A further independent tool, linguistics, has contributed hypothetical reconstructions of early European languages and family trees with estimates of dating of splits, in particular theories on the relationship between speakers of Indo-European languages and Neolithic peoples. Some archaeologists believe that the expansion of Neolithic peoples from southwest Asia into Europe, marking the eclipse of Mesolithic culture, coincided with the introduction of Indo-European speakers, whereas other archaeologists and many linguists believe the Indo-European languages were introduced from the Pontic-Caspian steppe during the succeeding Bronze Age.