Haplogroup I-M253, also known as I1, is a Y chromosome haplogroup. The genetic markers confirmed as identifying I-M253 are the SNPs M253,M307.2/P203.2, M450/S109, P30, P40, L64, L75, L80, L81, L118, L121/S62, L123, L124/S64, L125/S65, L157.1, L186, and L187. It is a primary branch of Haplogroup I-M170 (I*).
Haplogroup I1 is believed to have been present among Upper Paleolithic European hunter-gatherers as a minor lineage but due to its near-total absence in pre-Neolithic DNA samples it cannot have been very widespread. Neolithic I1 samples are very sparse as well, suggesting a rapid dispersion connected to a founder effect in the Nordic Bronze Age. Today it reaches its peak frequencies in Sweden (52 percent of males in Västra Götaland County) and western Finland (more than 50 percent in Satakunta province). In terms of national averages, I-M253 is found in 38-39% of Swedish males, 37% of Norwegian males, 34.8% of Danish males, 34.5% of Icelandic males, and about 28% of Finnish males. Bryan Sykes, in his 2006 book Blood of the Isles, gives the members – and the notional founding patriarch of I1 the name "Wodan".
All known living members descend from a common ancestor 6 times younger than the common ancestor with I2.
Before a reclassification in 2008, the group was known as I1a, a name that has since been reassigned to a primary branch, haplogroup I-DF29. The other primary branches of I1 (M253) are I1b (S249/Z131) and I1c (Y18119/Z17925).
More than 99% of living men with I1 belong to the DF29 branch which is estimated to have emerged in 2400 BCE. All DF29 men share a common ancestor born between 2500 and 2400 BCE. The oldest ancient individual with I1-DF29 found is Oll009, a man from early Bronze Age Sweden.
Origins
While haplogroup I1 most likely diverged from I* as early as 27,000 years ago in the Gravettian, so far DNA studies have only been able to locate it in three Paleolithic and Mesolithic hunter-gatherers. As of November 2022, only 6 ancient DNA samples from human remains dating to earlier than the Nordic Bronze Age have been assigned to haplogroup I1:
A hunter-gatherer from the Azilian in Spain in 11,466 BCE classified as having a now extinct branch of I-Z2699. Burial SF11 Date: 7500 BP - The first is a DNA sample from a Scandinavian hunter-gatherer with the label SF11 found on Stora Karlsö on Gotland. SF11 was found to have carried 9 of the 312 SNPs that define haplogroup I1. SF11 was classified as I1-Z2699*. SF11 was not assigned to a specific archaeological culture due to the skeleton being found in the Stora Förvar cave on Stora Karlsö. Burial BAB5 Date: 7300-5900 BP - The second is an individual sample from Balatonszemes-Bagodomb labelled BAB5, from Neolithic Hungary. BAB5 was found to have carried 1 of the 312 SNPs that define haplogroup I1. BAB5 may also be classified as I1-Z2699*. BAB5 had a genetic affinity to other contemporary Neolithic farmers of Central Europe. Burial RISE179 Date: 4010-3776 BP - Additionally, the third ancient I1 sample is from an individual found in a kurgan burial dating to the late Neolithic Dagger Period in Scandinavia labelled RISE179. The grave is located close to Abbekås on the south coast of Skåne RISE179 had a genetic affinity to the populations of the Corded Ware culture and the Unetice culture. Burial oll009 Date: 3930-3750 BP - The fourth ancient I1 sample predating the Nordic Bronze Age (1700–500 BCE) is labelled oll009 and was sequenced in the study titled "The genomic ancestry of the Scandinavian Battle Axe Culture people and their relation to the broader Corded Ware horizon". Oll009 is dated to the Scandinavian late Neolithic and was found in a burial in Sweden close to Öllsjö on the east coast of Skåne. Similar to RISE179, he carried a high percentage of Western Steppe-Herder ancestry and had a genetic affinity to the population of the Battle Axe culture and other populations of the Corded Ware horizon. oll009 has Y11204 but does not seem to have Y164553 or Y11205.
Despite the high frequency of haplogroup I1 in present-day Scandinavians, I1 is completely absent among early agriculturalist DNA samples from Neolithic Scandinavia (which also is the case with other haplogroups across Europe). Except for a single DNA sample (SF11), it is also absent from Mesolithic hunter-gatherers in Scandinavia. I1 first starts to appear in Scandinavia in notable frequency during the late Neolithic in conjunction with the entrance of groups carrying Western Steppe Herder ancestry into Scandinavia, but does not increase significantly in frequency until the beginning of the Nordic Bronze Age.