Scholars have proposed different theories on the origins of the Mycenaeans. According to one theory, Mycenaean civilization reflected the exogenous imposition of archaic Indo-Europeans from the Eurasian steppe onto the pre-Mycenaean local population. An issue with this theory, however, entails the very tenuous material and cultural relationship between Aegean and northern steppe populations during the Bronze Age. Another theory proposes that Mycenaean culture in Greece dates back to circa 3000 BC with Indo-European migrants entering a mainly depopulated area; other hypotheses argue for a date as early as the seventh millennium BC (with the spread of agriculture) and as late as 1600 BC (with the spread of chariot technology). In a 2017 genetic study conducted by Lazaridis et al., "the Minoans and Mycenaeans were genetically similar, [but] the Mycenaeans differed from Minoans in deriving additional ancestry from an ultimate source related to the hunter–gatherers of eastern Europe and Siberia, introduced via a proximal source related to the inhabitants of either the Eurasian steppe or Armenia." However, Lazaridis et al. admit that their research "does not settle th[e] debate" on Mycenaean origins. Historian Bernard Sergent notes that archaeology alone is not able to solve the issue and that the majority of Hellenists believed Mycenaeans spoke a non-Indo-European Minoan language before Linear B was deciphered in 1952.