Preprint Allentoft et al. 2024

The preprint of the study estimates the age of the I1 male population of Southern Scandinavia to be around 4000 years and defines the direction of their arrival as northeast. The time period coincides with the late Scandinavian Neolithic (Scandinavian Dagger Period) and the early Scandinavian Bronze Age. The newcomers are connected to the stone cist burial, a new type of burial common in southern Scandinavia. The burial method in question was common in Gotland as well, and the oldest graves in this area in Estonia are associated with western influences and migration from the west (interestingly, the Gotland saga, Gutasaga, mentions a migration to an island in Estonia, probably to Saaremaa and also to Poland.  Then the Danish prehistorical tradition tells about elite groups who migrated from the north, warred against jutes and beat them.  They formed the root of Danes). Later, the Scandinavian influence decreased in Estonia and a new burial method, the Tarand burial, took its place.

Today's oldest I1 clades based on living human samples are 4600 years old. The oldest I1 samples based on ancient DNA are 7000-7500 years old and were found in Gotland (Stora Förvar 11) and Hungary (BAB5). The Hungarian sample exclusively represents the early European Neolithic population, while the Gotland sample represents mainly local hunter-gatherers, but with a piquant European Neolithic addition. As a side note, Sweden's most common clade, L22, is 3900 years old according to the Yfull website, the main group of Finnish I1 men is 2300 years old and its upstream group is 2800 years old.  Regarding to the Estonian I1 we know only the size of proportion, because so far the research has shed light only on clades of Estonian haplotypes N1 and R1a.  The proportion of Estonian I1 is 15% according to earlier studies.

Stone cist graves in Gotland

Stone cist graves in Estonia

Estonian Tarand graves, usually connected to the Baltic Finnic migration from the east.  Tarand graves followed the stone cist period.  

In Finland, Bronze Age graves are common, there are thousands of discovered Bronze Age graves and stone cairns assumed to be graves, but I could not find maps specific to the grave type. After reading several archaeological studies related to stone cist burials, I am still unsure of their origin and historical chronology. One of the reasons for this may be that archaeologists did basic research in both Finland and Sweden before the digital revolution, and these studies are not available online.