Things to get right out of the way:
1. I will reference an unpublished draft work that has not been peer-reviewed. So, although the author is way better at math, probabilities, and genetics than I am, this work reflects them talking about their hobby with some good authority. It is well-informed and more technical than one of my posts, but it is citizen science. It is a labor of love from a scientist in a completely different field.
2. I am biased. If you’ve looked back at my older posts, you can see I blame the Danes and the proto-Danes fairly often for R-CTS12023/R-DF95 (and have for over a decade). I have put forward a lot of different possible theories, but this is one of my favorites. In this one, I view the Jutland Peninsula as a lawn sprinkler periodically infecting the rest of Europe with waves of my male line kin. This draft paper is playing right into that bias.
In the Wayback Machine
Where I am in the Northern Hemisphere, the winter solstice has meant dark days and long nights. Typically, we eat too much, drink too much, light things on fire, and give each other presents around this time of year. This winter, Iain McDonald gave the U106 group a gift in the form of a draft paper looking at the possible origins of U106 and its major branches. The paper is titled Phylogeography of R-U106.
Over the years, as a group, Y DNA enthusiasts have been pining for actual ancient DNA that reached some meaningful depth. Ancient DNA that gets into the branches of the major SNPs. I suspect we’re in a golden age for that kind of research. Ancient Y DNA and MTDNA are tagging along with full genome analysis for ancient remains. The focus is typically autosomal DNA, but Y DNA and MTDNA are along for the ride.
Coupled with that, it seems like every study of ancient remains now contains some place or plan for genome analysis. Again, maybe not the main feature, but part of the overall picture. Y DNA and MTDNA are packaged with real cultural and genetic context. That makes these educated guesses better each time.
Previously, the oldest U106 person (RISE98) was found in Lilla Beddinge, Sweden circa 2200 BC. In 2024 another U106 person of a similar age to RISE98, if possibly slightly older, CGG106838 was found in Zealand Denmark. CGG106838 is down the R-Z301 branch under a brother branch to R-Z18, labeled FTT8.
You can get an overview of the siblings of R-Z18 on FTDNA’s site.
In 2021 our new oldest U106 man, PLN001, was found in Plotiště nad Labem, Czechia. He was buried around 2900 BC, 700 or so years before the previous two men I’ve mentioned. He is an early Corded Ware Culture person with a strong Yamnaya autosomal mix. R-U106 and its parent Y SNP, R-L151, have not been found among the Yamnaya. Our man is possibly a descendant of an undiscovered Yamnaya offshoot group, a proto-Yamnaya group, or he gets his Yamnaya-like autosomal DNA from maternal sources. Any mix of those things seems reasonable.
The Corded Ware culture has some gene flow with the Yamnaya, but the most common Y SNP among the Yamna is R-Z2103, a brother branch to R-L151, which eventually leads to R-U106.
The basic idea I get is that we R-Z18 men have a launch pad of Corded Ware people with inter-related steppe ancestry, westward and northern movement, some mysterious gaps to fill in, and about 700 plus years to play with before the oldest R-Z18 person pops up. That assumes that PLN001 is pretty close to the beginning of R-U106.
RISE98’s Slightly Younger Cousins in R-Z18
CGG106838 and RISE98 show that there are U106 men in different branches floating around in modern Denmark and Southern Sweden circa 2200 BC. Family Tree DNA estimates that R-Z18 appeared around 2250 BC. R-Z18 is a decently sized branch under U106, but it is not an immediate child of U106. FTDNA has R-BY30097 and one step farther back, R-Z2265, before reaching R-U106.
The FTDNA estimated gap between R-BY30097 and its child R-Z18 is roughly 600 years. That is a long time for only a single mutation. Either I’m not thinking about it right or something is off. In any case, right around 2200 BC there are U106 peeps in the Nordic zone and the first R-Z18 people are found in that same zone.
These R-Z18 people are presented the McColl study. I made some notes on this study earlier in the year. I commented then that the depth of Y DNA analysis seemed to be kept at a high level. Though not the focus of the study, the amount and timing of R-Z18 samples were worth commenting on by the researchers. They considered the R-Z18 men to be locals in some respect.
FTDNA hasn’t included these results yet in their ancient connections for R-Z18, but I’m hoping they will get access to the raw data and be able to push on these Y results a little more. Here is a close-up of those oldest results on a map of Zealand, Denmark, and Skane, Sweden. They lived and died at the end of the Neolithic and the beginning of the Nordic Bronze Age. There are several men from Karlstrup. The single map point can be misleading; five men are represented on this map.
Back to the Draft U106 Origins and R-Z18
Iain’s paper is well worth the read and his broader scope gives an excellent overview of the different branches of U106 moving through Europe. I will selfishly focus on R-Z18 and the lead-up to it.
Iain points out that burials began to be dominated by U106 or proto U106 men around 2300 BC, where previously R1a men from the corded ware culture dominated. These new people coincide with the Bell Beaker culture. They infiltrate Jutland and then move over the islands to southern Sweden. The majority of the new bronze age burials were R-Z18.
Borrowing from Iain’s paper: R-Z18 represents 37% of U106 testers in Scandinavia today (14% of the total population of U106), but with 9 out of 11 of these burials being R-Z18, it was probably a much higher percentage of the U106 men at the time of these samples (maybe a percentage in the high 70’s) . The estimated origin of R-Z18 is roughly 2300 BC, which puts this plethora of R-Z18 men from roughly 2100 BC right near their source ancestor in time. R-Z18 is so prominent that other samples that are stuck higher up the Y tree are likely R-Z18 results that could not be determined because of degradation.
Iain McDonald’s idea is similar to the McColl study authors’ informal conclusion. R-Z18 appears to be a local variant under R-U106 and BY30097. It is probable that late neolithic or early bronze age Jutland is the source of R-Z18 and that it spread quickly to the Danish Islands and Southern Sweden in those early years with peak saturation around 1900 BC.
The McColl paper touched on this too, but other R-U106 groups don’t seem to show up in any great number for a couple of thousand years. Iain McDonald has multiples of other U106 clades, arriving in Scandinavia around 300 BC.
I steal a lot of great map content from authors around the internet, and this time is no different. Here is a nice pictorial representation from Iain Mcdonald of the various movements of major branches of R-U106 from a bird’s eye view. R-Z18 in grey moves out from its starter zone centered on the Danish Islands spreading north, east and then later west.
Note the question marks at the end of the word homeland. There is always room to learn something new. At this moment, though, we have further evidence of an ancient northern refuge for R-Z18 (and subgroups). Where we move from there, and where we’ve ended up, is a much more personalized journey.