A Swedish book (Bojs and Sjölund, Svenskarna och deras fäder, 2016) that is based on the (FamilyTree) analyses of the full genomes of 3000 contemporary Swedes concludes that Y-haplogroup I1 (=I-M253) arrived in great number into Scandinavia from the proximity of Halle (at Saale) in northern Germany beginning in the 16th century BC (the book also claims that I1 originated in this area about 3000 BC).
Incidentally, Halle also happens to be where W. Euler (Sprache und Herkunft der Germanen, 2009) places his Germanic "Urheimat", i.e. the linguistic root of Germanic that explains its Italic influences (Italic tribes dwelled in Bohemia south of Halle). Halle was the northern center of the leading Bronze Age Unetice culture, which is associated with the Sky Disc of Nebra and the impressive mound in Leubingen. The Unetice culture disappeared suddenly in the beginning of the 16th century BC, which fact can have motivated the emigration to Scandinavia where also new business opportunities opened with European demand for amber (available at the Baltic coasts). As a consequence of the immigration, the Nordic Bronze Age exploded in the 16th century BC as though "everything was put in place at once" (sv.Wikipedia).
Thus, it seems that I1 developed in a quite dramatic way: They began as European hunter-gatherers who joined the agricultural society and many centuries later some of them joined the Indo-European band-wagon so successfully that they could establish a clan of their own in the northern Unetice culture where they learnt bronze technology and built the Leubingen mound. When this culture disintegrated they buried the Sky Disc of Nebra and went to Scandinavia where they triggered the Nordic Bronze Age and took part in the creation of Germanic.
Kaj, is there an English text about the content of the book? Its exactly the view I think is correct and I would like to get to know more about it.
Ithink the story of I1 is similar to others, in which one clan rose to prominence in tumultuous times which gave small groups of men the opportunity to gain a dominant position over larger regions and expanding from there on.
We see it in Palaeolithic, latest Mesolithic times already. For Northern-Central Europe and I1 I would propose a scenario like that: Mesolithic (like Villabruna) carriers of I replace earlier inhabitants of Europe which survived the LGM, Neolithic G2a and E replace those while spreading organised farming, but take up some I2 local males, which take over during the turn to more warlike agro-pastoralism and replace in the North G2a. Now my assumption would be, that the ancestor of modern I1 was part of this takeover we can observe with I2. It lurked, most likely, around in groups of TRB, GAC or Baden Culture, when the big thrust from the East brought the steppe lineages (R1a/b CWC, R1b BBC and Yamnaya).
The next phase is that the exclusive BB rule was succeeded by a more mixed, Corded Ware related group with Carpatho-Balkan influences, which resulted in the more diversified Unetice Culture. This is when I1 could have gained a favourable position in Northern Central Europe, probably even coming from Pannonia or the Carpathian region, but this is completely unknown so far without having the right samples. But Unetice went into a crisis, probably also because being attacked by chariot drivers from the East and was replaced by more warlike, clan-based pastoralists once more, resulting in the Tumulus culture. So Unetice did experience a real collapse of its established structures which might have resulted in an actual mass migration, not just the flight of individuals here and there.
Do the authors of the Swedish book contradict this explanation on any level? Do they write anything about where in those Middle to late Neolithic cultures they think I1 survived and spread first?
It is possible that the story I propose is true, generally speaking, but I1 was not part of the Unetice flight, but rose to importance during this time from the local, pre-NBA inhabitants. Because locals could have used their chances like the newcomers, we can't know for sure.