Genetics
R1a1a (R-M17 or R-M198) sub-clade is the one most commonly associated with Indo-European speakers. Most discussions purportedly of R1a origins are actually about the origins of the dominant R1a1a (R-M17 or R-M198) sub-clade. Data so far collected indicates that there two widely separated areas of high frequency, one in South Asia, around North India, and the other in Eastern Europe, around Poland and Ukraine. The historical and prehistoric possible reasons for this are the subject of on-going discussion and attention amongst population geneticists and genetic genealogists, and are considered to be of potential interest to linguists and archaeologists also. Recent findings indicate that R1a's origin is likely to be in South Asia, but probably at a date earlier than the expansion of the Indo-Iranian language family.
Out of 10 human male remains assigned to the Andronovo horizon from the Krasnoyarsk region, 9 possessed the R1a Y-chromosome haplogroup and one C-M130 haplogroup (xC3). mtDNA haplogroups of nine individuals assigned to the same Andronovo horizon and region were as follows: U4 (2 individuals), U2e, U5a1, Z, T1, T4, H, and K2b.
90% of the Bronze Age period mtDNA haplogroups were of west Eurasian origin and the study determined that at least 60% of the individuals overall (out of the 26 Bronze and Iron Age human remains' samples of the study that could be tested) had light hair and blue or green eyes.
A 2004 study also established that during the Bronze Age/Iron Age period, the majority of the population of Kazakhstan (part of the Andronovo culture during Bronze Age), was of west Eurasian origin (with mtDNA haplogroups such as U, H, HV, T, I and W), and that prior to the 13th-7th century BCE, all Kazakh samples belonged to European lineages.
Read more about this topic: Indo-Iranian Peoples