From an archaeological perspective, the earliest IA burials associated with nomad-warrior cultures were identified in the eastern fringes of the Kazakh Steppe, in Tuva and the Altai region (ninth century BCE).
Following this early evidence, the Tasmola culture in central and north Kazakhstan is among the earliest major IA nomad warrior cultures emerging (eighth to sixth century BCE).
These earlier groups were followed by the iconic Saka cultures located
Interesting excerpts (emphasis mine, changes for clarity):
Here, we report the first genome-wide data of 10 ancient individuals from northeastern Xinjiang. They are dated to around 2,200 years ago and were found at the Iron Age Shirenzigou site. We find them to be already genetically admixed between Eastern and Western Eurasians. We also find that the majority of the East Eurasian ancestry in the Shirenzigou individuals is related to northeastern Asian populations,
The positions of non-Tagar Iron Age groups in the MDS plot were correlated with their geographic position within the Eurasian steppe belt and with frequencies of Western and Eastern Eurasian mtDNA lineages in their gene pools. Series from chronological Tagar stages (similar to the overall Tagar series) were located within the genetic variability (in terms of mtDNA) of Scythian World nomadic groups (Figs 5 and 6; S4 and S6 Tables). Specifically, the Early Tagar series