So, what's your explanation for why I1 folk went from apparently not existing in Scandinavia to greatly outnumbering the I2 folk who had previously dominated the area? Any time a haplogroup has increased dramatically in numbers, agriculture has been part of it, since that permits larger families than the hunting and gathering lifestyle does. There are still a lot of gaps in our knowledge of exactly how the modern population of Scandinavia was created, and even more with respect to the Baltic, but can you show me any evidence of a large I1 population that was pre-agriculture?
I think that I1 were the hunters that moved into Scandinavia from Finland and lived along the North Coast, I2 were the continential ones that lived along the southern coast of Scandinavia and the North Sea.
I2a2 isn't extinct in Scandinavia also, there is still I2a2 and some I2a1. I2a2 exists at in around 10% in some regions of Sweden as does I2a1, together they make up about 7% of the total population. This isn't much but consider that hunter gather mtDNA U5b/a also make up less than 10% of the overall total population. Mesolithic Scandinavia & Nothern Europe in general was entirely different geographically from modern day, maybe I1 even came from Doggerland who knows. The existence in Finland though shows that it expanded independent from any other group.
The Nordic Bronze Age was characterized first by a warm climate that began with a climate change around 2700 BC (comparable to that of present-day central Germany and northern France). The warm climate permitted a relatively dense population and good farming; for example, grapes were grown in Scandinavia at this time. A wetter, colder climate prevailed after a minor change in climate between 850 BC and 760 BC, and a more radical one around 650 BC.
The cultural change that ended the Bronze Age was affected by the expansion of Hallstatt culture from the south and accompanied by a deteriorating climate, which caused a dramatic change in the flora and fauna. In Scandinavia, this period is often called the Findless Age due to the lack of finds. While the finds from Scandinavia are consistent with a loss of population, the southern part of the culture, the Jastorf culture, was in expansion southwards. It consequently appears that the climate change played an important role in the southward expansion of the tribes, considered
Germanic, into continental Europe
[1]. There are differing schools of thought on the interpretation of geographic spread of cultural innovation, whether new
material culture reflects a possibly warlike movement of peoples ("
demic diffusion") southwards or whether innovations found at Pre-Roman Iron Age sites represents a more peaceful
cultural diffusion. The current view in the Netherlands hold that Iron Age innovations, starting with Hallstatt (800 BC), did not involve intrusions and featured a local development from Bronze Age culture.
[13] Another Iron Age nucleus considered to represent a local development is the
Wessenstedt culture (800 - 600 BC).
The bearers of this northern Iron Age culture were likely speakers of Germanic languages. The stage of development of this Germanic is not known, although
Proto-Germanic has been proposed. The late phase of this period sees the beginnings of the
Germanic migrations, starting with the invasions of the
Teutons and the
Cimbri until their defeat at the
Battle of Aquae Sextiae in 102 BC, presaging the more turbulent
Roman Iron Age and
Age of Migrations.