The expansion of Y-DNA subclade R-Z93 (R1a1a1b2), according to Mascarenhas et al. (2015), is compatible with "the archeological records of eastward expansion of West Asian populations in the 4th millennium BCE, culminating in the socalled Kura-Araxes migrations in the post-Uruk IV period."[38] According to Pamjav et al. (2012), "Inner and Central Asia is an overlap zone" for the R -Z280 and R -Z93 lineages, implying that an "early differentiation zone" of R-M198 "conceivably occurred somewhere within the Eurasian Steppes or the Middle East and Caucasus region as they lie between South Asia and Eastern Europe". [39] According to Underhill et al. (2014/2015), R1a1a1, the most frequent subclade of R1a, split into R-Z282 (Europe) and R-Z93 (Asia) at circa 5,800 before present,[40] in the vicinity of Iran and Eastern Turkey. According to Underhill et al. (2014/2015), "[t]his suggests the possibility that R1a lineages accompanied demic expansions initiated during the Copper, Bronze, and Iron ages."[41]