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“Tracing past human male movements in northern/eastern Africa and western Eurasia: new clues from Y-chromosomal haplogroups E-M78 and J-M12.” Cruciani et al. (2007)

While caution should be exercized when attributing the genetic features of modern populations to prehistoric events, it is nonetheless worthwhile to try to locate a signature of expansion into the interior Europe from the Balkans consistent with the dates given by D'iakonov (5th to 3rd millennium BC). In a recent article [Cruciani et al. (2007) “Tracing past human male movements in northern/eastern Africa and western Eurasia: new clues from Y-chromosomal haplogroups E-M78 and J-M12.” Molecular Biology and Evolution 24(6): 1300-1311], such a signature was found for two Y chromosome haplogroups, E-V13 and J-M12. The authors determined that the frequency of these two haplogroups is correlated, i.e., a high frequency of one statistically predicts a high frequency in the other, suggesting a common history:
In order to evaluate whether the present distribution of these two haplogroups can be the consequence of the same expansion/dispersal microevolutionary event, we first compared the two frequency distributions in Europe (J-M12 frequencies obtained from both published and new data; supplementary table 2). We observed a high and statistically significant correspondence between the frequencies of the two haplogroups (r=0.84, 95% C.I. 0.70-0.92).
The authors further studied the features of Y chromosomes within these two haplogroups in Europe, detecting a star-like pattern.
We then constructed a microsatellite network of 43 European J-M12 chromosomes (supplementary table 3) and found a clear star-like structure (fig. 4C), a further feature shared with E-V13.
Such a pattern emerges when individual Y chromosomes, deviate over time from a single founder individual. This means that, by and large, E-V13 and J-M12 in Europe can be traced to two individual men of the past. The next step would be to determine when the expansion of their descendants took place:

By taking into consideration two different demographic expansion models (see methods), we obtained TMRCA estimates very close to those of E-V13, i.e. 4.1 ky (95% C.I. 2.8-5.4 ky) and 4.7 ky (95% C.I. 3.3-6.4 ky), respectively. Thus, the congruence between frequency distributions, shape of the networks, pair-wise haplotypic differences and coalescent estimates point to a single evolutionary event at the basis of the distribution of haplogroups E-V13 and J-M12 within Europe, a finding never appreciated before [...] Our estimated coalescence age of about 4.5 ky for haplogroups E-V13 and J-M12 in Europe (and their C.I.s) would also exclude a demographic expansion associated with the introduction of agriculture from Anatolia and would place this event at the beginning of the Balkan Bronze Age, a period that saw strong demographic changes as clearly testified from archeological records (Childe, 1957; Piggott, 1965; Kristiansen, 1998). The arrangement of E-V13 (fig. 2D) and J-M12 (not shown) frequency surfaces appears to fit the expectations for a range expansion in an already populated territory (Klopfstein, Currat and Excoffier 2006).

Thus, Y chromosome haplogroups E-V13 and J-M12 in Europe seem to have expanded from the south Balkans at the beginning of the Balkan Bronze Age. Moreover, similarly to the results reported by Pericic et al. (2005) for E-M78 network α, the dispersion of E-V13 and J-M12 haplogroups seems to have mainly followed the river waterways connecting the southern Balkans to north-central Europe, a route that had already hastened by a factor 4-6 the spread of the Neolithic to the rest of the continent (Tringham, 2000; Davison et al. 2006).
The authors do not attempt to relate this expansion to a linguistic spread, but its timing is consistent with the model of the Indo-Europeanization of Europe from a proximate Balkan source at the Early Bronze Age.