In early 2000s we used to discuss how the rise of the 1st Hun (Xiongnu) Khaganate resulted in a transition of the steppe from I-Ir to “Altaic”. But we had little idea about the dynamics. But we aDNA we actually see that in action: Note the 2 Hun representatives shown below. One groups with the usual “Altaics” while the other fall in the old IE clade.
Thus, as suggested by philology & linguistic there was an I-Ir component in Mongolia itself in the Xiongnu Khaghanate. This explains some memetic features, alcohol types, probably equestrian capabilities & more speculatively transmission of origin mythologies to the chIna-s like the Pan gu myth ~ puruSha. One also wonders if the predilection for brAhmI in the subsequent Khaghanate was influenced by these I-Ir elements within the hUNa-s.