I accept finally the Jaska's opinion: germanic could be ancient in Scandinavia, even if that don't prove the germanic formation took place there OR only there -
I 'm trying to put things one with another : not very easy !
1- H.HUBERT thought germanic People was a mix of nordic people (yet a mix of hunters-gatherers and neolithic peasants ?) indo-europeanized by bearers a culture he named 'carpodace', I suppose coming previously from the North Carpathians or through Carparthians ; I think he saw them as a kind of Illyrians. I don't remember (I have no more the book) where he placed the complete germanization (and first shift). I note illyrian is classified satem by linguists – Corded could have been spoken a partially satemized language -
2- linguistically, some scholars says : germanic shows very late contact with celtic languages, old contacts with italic languages, and between both, contacts with a partially satemized languages or an old form of I-E not evolved completely towards a centum or satem position. This not well evolved or partially satemized language could have been the Corded's one = 1- (I recall the possible satemic substrata in Saami finnic). Male elite Y-R1a (Z645/Z283/Z282 lately >?>Z284? # Z458)
3- on an other side, Y-R1b-U106 seams having evolved in Northern Europe (hypothesis A), being « rich » enough even along Baltic shores until Estonia (it's true that germanic tribes occuped Baltic lands, supposed they were being got down from Scandinavia, and that later « Teutons » knights recovered N-E Europe on cost of Slavs). U106 could have been there in ancient enough times, as Y-R1b-L10 is represented in Northern Europe along with other R1b-subHGs of R-P312... Nevertheless we can imagine a set of Y-R1b-U106 came along with some Y-I2a2 from East Carpathians-West Urkaina (hypothesis B) at Bronze Age or even at B.B. Times (-2500?), passed between future italic(-celtic) Y-R1b-P312(+ some Y-I2a1b) and Corded people along Danau river but taking more northwards in Bohem (Oder, Saale, Elbe rivers) and merging with Corded in Thuringen/S-Saxony-Anhalt : I rather think U106 as a whole separated completely from other Y-R1b even if they merged with their cousins soon enough after due to several movements, present days distribution is clear enough – I keep in mind that an heavy 'corded' demic element was present at some Unetice periods (non-metric survey of teeth + metric surveys) with very lighter element of B.B. Origin (greater influence for culture than for genes) but that as a whole the Unetice population was more homogenous considering males & females, and somewhat different (I thought first it was only the neolithic people element which give differences but perhaps I was wrong)) : I can think too that some centum I-E other than neolithic people element was taking part in Unetice development – I should not be surprised if some more numerous surveys about ancient DNA tought us that some Y-R1b-U106 was already present beside a lot of Y-R1a among Corded people – so : ancient contact at the southern merges of Corded culture between Y-R1a and Y-R1b-U106 without any conclusion about culture here -
4- we can imaginea possible intermediate centum I-E language that could be the famous but not to well known 'northwest block I-E'– some shared words in germanic and satem languages could be loan words by baltic and slavic contacts, whatever the direction of movement, and not only PIE cognates : I have not the knowledge to answer ; this N-W block can have been the language of the bulk of Y-R1b-U106 – the apparently cognates words anterior to the germanic shift could be recent enough, spite of that... when comparing I-E modern languages, slavic and baltic « sons » don't show very more links to germanic than any other european I-E descendant – phonetically concerning PIE *Bh- , *Dh-, *Gh-, slavic is like germanic, but celtic too..., the three of them separated from hellenic and italic for these evolutions but it is rather italic and hellenic that seam marginal here -
5- finally, the germanic quality seam officially acquired lately, not before the 1000 BC, and so not preceding the Iron Age (Hallstatt) which saw some tribes movements from Austria-Bohemia areas northwards to Southern Scandinavia – a lot of skeletons proved that, showing an (elite only?) mixture of numerous near 'nordic' types with rarest other types ('danubian' like among them, certainly of previous neolithic stock, and represented more by autosomals than by Y-DNA, and some 'kymric' or 'iron-celtic' influence too : lower crania, shorter faces : interesting because very different from both 'corded' and 'danubian' types, and 'corded' types dominated in Eastern Hallstatt, so the people that « climbed » to Denmark at Iron Ages showed some Western Hallstatt mixing) – so this near 'nordic' type was not indentical too 'corded', so certainly Y-R1a was surely present but I don't discard the Y-R1b-U106 and lesser yet Y-R1b-P312 and downstreams... the contemporan U106 of Austria are a thorn in my foot : I don't know if they have been present there for a long time (the genitors of the portion of U106 I should place very easy among the first Belgae Celts, centred on Bohemia perhaps) or if they represent the later arrived Germanics from North ??? I avow I don't imagine the 60% U106 in Y-R1b as only from celtic times... and Belgae had the possibility to take U106 from more northern lands... my meaning of an ancient northern well separated position for Y-R1b-U106 still seams the best explanation of today distribution -
6- when reading about Trichterbecher and Jastorf in Wikipedia, and too germanic languages , I concluded that neolithical Trichterbecher was of Long Barrows culture inspiration or at least dominance, atlantic and maritime – the ancient germanic loan words in finnish are anterior to Jastorf culture, seamingly, according to someones – if true, that could prove the germanic or proto-germanic was spoken yet in Scandinavia before Iron Age and that the Hallstatt « Ironers » going to Denmark was more on the celtic side and just influenced positively the late mix of Trichterbecher + Nordic Bronze Age to create Jastorf and neighboring cultures : period of the celtic loanwords in germanic ? -
7-the problem of the shift is very boring because we can assume that some populations in Central Europe had the 'hardning' or 'unvoicing' tendancy (see the second high germanic shift and the same tendancy to invoicing in hungarian, according to some linguists, and I think in genuine rhaetic language) and the finnic languages have the same one... people merging with Celts who have the inverse tendancy! In modern german language the focus appears being south the Danau river, in Switzerland and Austria, maybe rhaetian ? (but I suppose diverging facts are more reliable than converging facts?) so the question of geographical source of unvoicing is still there – and it is not sure that the Iron Age people going northwards was the cause of the shift, upon all if they was of celtic inspiration : rather the contrary ...
8- So for me, some Y-I1 quasi autochtonous bearers passed in Scania from South Baltic shores, through Denmark : unknown language for me – some mixtures of neolithic southeaterners and of atlantic megalithers (Y-R1B-P312>>-L21 in the mix?) settled in the same regions after, maybe already I(E speakers, maybe not) – at Chalcolithic times or Early Bronze Age, a lot of Y-R1a ('corded') passed through Denmark , surely with Y-I1 and some rarest Y-R1b-U106 : quasi sure : I-E language partially satemized – only after, but before Iron Age, a contribution of B.B. People (centum) of unknown previous DNA, but having accultured a lot of R1b people (more P312/U152 around south Rhinelands, more U106 around north Rhineland and frisia) and the osmose subseuqnelty made like that with ancient nordic (first I1s) habits gave way to the proto-germanic language where the 'nordic' package were very scarce and that have been completed by celtic loanwords only after – I don't oppose Denmark (continental) from Scandinavia : I believe it has been the strongest center of attraction and diffusion (« market », « pass ») - I think the BB accultured people was centum I-E speakers, but not celtic (northwest I-E) or not already celtic – the U152 of North Denmark and southern coastal Norway could very well be linked to celtic Cimbri and Teutons, after all : from Bohemia Hallstatt ? I red the cauldron from Denmark, considered and denied as celtic, show technics and some stuff of celtic Gallia or Bavaria – the language shift in germanic could well have taken place in or close around Scandinavia, and we are not obliged to separate continent and Scandinavia for the cristallization of germanic -
Just some thoughts – a try to summarize and synthetize -