Yaz I culture is argued to be related to the sedentarisation of the nomadic Indo-Iranians in the Eurasian Steppe, a synthesis with autochthonous traits. It extended from the central part of the Kopet Dag mountains to the fertile delta of the Murghab River. It is characterised for total lack of necropolises and tombs, as well as painted ceramic with triangle and ladder patterns. Recent research shows four groups of patterns, the triangular (triangles and chevrons), lozenges, bands, and of additional elements. It seems to be connected to the Chust culture of Fergana Valley, Mundigak V-VI in Sistan, and Pirak I-III on the Kacchi Plain. Compared to the Chust culture, no tombs from the Yaz culture have been found. Asko Parpola and Fred Hiebert argued that these cultures seemingly derived from the Haladun culture (1750-1200 BCE) of Xinjiang, and some Andronovo culture contacts, indicating a Europid upper strata who spoke East Aryan. The introduction of the culture is seemingly related to the sound change *s > h when Iranian language came in the Indo-Iranian borderlands of Rgvedic tribes around 1500 BCE, seen in the change of the Vedic river Sindhu into Avestan Hindu (Indus River), Sarasvati into Haraxhvaiti.