This important work on the ethnogenesis of the Mongols has been finally published. A few comments follow:
https://www.sciencedirect.com/science/article/pii/S0092867420313210?via%3Dihub
First around 3300 BCE and before. The red is the Afanasievo: the 1st Indo-European invasion of the East. What is striking (to me at least) is that

some of the Bactria Margiana (BMAC) ancestry is seen in the East (brow) the black and green are ancient north east Asian and ancient northern Eurasian. Next, around 2000 BCE+-200 yrs the second IE invasion of the east took place now likely by an Indo-Iranian group. This brought

the Sintashta ancestry (orange) into Mongolia. Another new ancestry appears in the form of the Baikal bronze age people in cyan. Even in the bronze age we see some admixture with the BMAC & Indo-Iranians. In the early Fe age by 1000 BCE we see that the BMAC is strongly resurgent

in the central Asian Eastern Saka communities. THis next brings us to the first Hun Khaganate, the Xiongnu. Here we see the imprint of the 3rd IE invasion of the Iranian Sarmatians (dark orange) & the emergence of the new dominant ancestry from the Chandman of NE Mongolia (pink)&

some east Asian Han-like Ancestry. This establishes beyond doubt the role of Iranian influx into Mongolia in the emergence of the 1st Hun Khaganate. Next we've the Blue TurK Uighur period during which that Chandman ancestry which started declining in late Hun period now vanishes

Here we see the 4th IE invasion of the East in the form of the Iranian Alani (blue). Finally we come to the Khitan and Chingizid Mongols where the East Asian Han like component becomes widespread & the Alan ancestry persists. This establishes beyond doubt the links the Mongolic

some Turkic people had with the steppe Iranians and earlier probably even with Sintashta Indo-Aryans. The admixture with BMAC seen here but not among Indians suggests that the invasion of India was swift& that group did not linger on with BMAC but cut through them to reach India