[2][16][17][18] In the region of Southern Central Asia, the Bronze Age Oxus civilization (or BMAC) was characteristic for irrigation and proto-state society based on long distance trade of raw materials and goods.

However, it suddenly disappeared in the Late Bronze Age (c. 1900–1500 BC), and in its place emerged the Early Iron Age (c. 1500/1400 - 1000 BC)[9] Yaz I culture with rural settlements based around fortified structures, control of irrigation systems, with specific hand-made ceramic type, as well as the almost complete disappearance of graves, compared to thousands of kurgans in the north.

[25] 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.

It is probably explained by the bloody revolt of Frada (521 BC) mentioned in Behistun Inscription in which reportedly 55,243 Margians were killed and 6,972 taken as prisoners, and the conquest of Bactria.

[38][39][40] The beak-shaped rim is replaced in form of a flattened roller, vessels are cylindrical-conical,[41] and a bronze three-bladed arrow, iron axes and adzes were discovered.

[42] The widely used name Yaz for the Iron age cultures of southern Central Asia is derived from the type site Yaz-Tepe.

A. Marushchenko initially introduced the term Epoch of Barbarian Occupation due to the "reduction of the area of the settlement and the decline of handcrafts" observed in the archeological record.

[2][52] It looked like a flattened circular hill with an area of 0.5 hectares and height 8 m. The structures were built on a clay platform surrounded by a defensive wall.

[2][53] The single purely Yaz I site in Tajikistan is Karim-berdy which measures 500 x 300 m.[54] Along the Kunduz River are located oasis Naibabad and Farukabad.

[51] There 20 Iron Age sites of Yaz I-III culture (1400–300 BC) in Serakhs oasis, the sub delta of Tedjen River in southern Turkmenistan.

A. Maruschenko considered northern pastoralist influence, V. M. Masson it is connected to the Namazga-Tepe VI, but with a break of 100–150 years in-between, while V. Sarianidi that the Yaz I assemblage arrived from eastern Khorasan.

[62] Recent research confirmed of the three the Masson's thesis that the Yaz I type ceramics in the foothill of Kopet Dag mountain are a natural development of the Late Bronze Age assemblage from Namazga VI period, but without any time lapse and external influence.

[69] Regardless, the identification of the Yaz culture with the civilization described in the Avesta is based on a number of factors that correlate the textual and archeological evidence.

A 2021 study by Kumar et al. shows how by the late Iron Age, the population of this region was characterised by a combination of BMAC and Andronovo ancestries.

[75] Likewise, a 2022 study also shows how the ancestry of modern Tajiks and Yaghnobis largely formed during the early Iron Age by a mixture between these two groups.

[76] Finally, a lack of graves and excarnations emerged in the Early Iron Age, especially in Yaz I and II cultures,[77] the same period in which Zoroastrianism developed (works such as the Gathas often being dated to the second half or end of the 2nd millennium BC); the contemporary occurrence falls in line with certain traditions (see Tower of Silence) and cultural schools of thought, but there is ongoing scholarly debate surrounding such a connection [2][78][79] There is evidence for excarnation in non-Zoroastrian cultures like those in Siberia and Mongolia, as well excarnation and dakhmas in some Bronze Age sites like Gonur Tepe and Altyndepe, thus it could have persisted into Early Iron Age as a notion for the long process of formation of the Proto-Zoroastrianism and Avesta.