About Proto-Germanic

[NewEnglander]

In reference to your last line, with the aDNA we have so far, there is in fact evidence that suggests a large-scale movement from Scandinavia into the Jastorf area and through the current more southerly Germanic regions at some unknown point during the IA: the emergence of I1 in the latter regions. Happy to repost on the current samples of various periods and areas if you like. 

I'll happily change my mind if the evidence shows differently in time, but currently I1 is demonstrated to have only got beyond stray finds and up to a significant representation resembling today's levels within the former Jastorf area and beyond in the Germanic south by the Migration Period.

There were 11 samples from the Netherlands in Patterson: one from the late IA, one from the Roman IA and the rest BA. None was I-M253+. What I really would like to see (and I'm sure you would too) is a proper aDNA paper on the Netherlands from the BA and right through the entire IA in particular because I think it would be the best area to test the hypothesis. Hopefully further studies will tell us more soonish about exactly when this influx of I1 DNA got underway in that and other more southerly Germanic areas.

Netherlands was never part of Jastorf. We need aDNA from northern Germany & Jutland

My understanding, correct me if I'm wrong, is that the primary method of burial for the Jastorf culture was cremation. We unfortunately may be out of luck here.